apoio financeiro da DFG (projectos SM 82 / 13-1) é reconhecido agradecimento.

1. Preparação de Solução Stock de pectina amidada <ol><li> Misturar 20 g de pectina amidada com 980 g de água (2,0% em peso). O grau de amidação é de 25% em peso. </li><li> Homogeneizar a solução com um agitador de alta velocidade (10.000 rpm) durante 2 minutos para se obter uma solução viscosa homogénea. </li><li> Medir o pH usando tiras de pH ou medidor de pH. Se o pH é inferior a 6,5, titula-se com NaOH 0,5 M para neutralizar a solução (a pH 7,0). </li><li> Adicionar carbonato de cálcio numa proporção de 0,1825 g por grama de pectina amidada seco (q = 1). &quot;Q&quot; denota o grau de reticulação. </li><li> Para 1 kg de solução de pectina amidada 2,0% em peso, adicionar 3,65 g de carbonato de cálcio (q = 1) 7 por 20,0 g de pectina seca. </li><li> Para uma maior reticulação, adicionar 0,3650 g de carbonato de cálcio por grama de pectina amidada seco (q = 2). </li></ol> 2. Produção de hidrogéis <ol><li> Homogeneizar a mistura carbonato de pectina / cálcio amidado usando o homogeneizador de alta velocidade (10.000 rpm) para se obter umdispersão homogénea branco. </li><li> Transferir a suspensão em moldes abertos ou de polipropileno placas de Petri de vidro. </li><li> Colocar os moldes na autoclave de alta pressão. Selar o autoclave. </li><li> Pressurizar a autoclave com o CO2 gasoso até 5 MPa, à TA. Consulte Gurikov et al. 7 para mais informações. Manter a pressão durante 24 horas. </li><li> Lentamente despressurizar o autoclave a 0,2 MPa / min. </li><li> Abrir o autoclave e remover os moldes. Retire os hidrogéis dos moldes por entregá-los. Se necessário, utilizar uma espátula. </li></ol> 3. Procedimento de solvente Troca <ol><li> Preparar 10 g de 10:90 (w / w) de etanol / água mistura por grama de hidrogel. </li><li> Mergulhar os hidrogéis no 10:90 (w / w) de uma mistura de etanol / água durante 12 horas. </li><li> Continue este processo com concentrações crescentes de etanol, isto é, entre 10:90 (w / w) de uma mistura de etanol / água a 30:70 (w / w) de etanol / água mistura. Após 12 horas, a transferência para 50:50 (w / w) de uma mistura de etanol / água, em seguida a 70:30 (12 horas), em seguida, 90:10 (12 horas) e, em seguida, uma solução de etanol a 100% (12 h). </li><li> Embeber o gel ainda mais em etanol puro para que a concentração final no interior do gel é mais do que 98% (w / w). Medir a concentração usando o medidor de densidade. O alcogel está agora pronto para CO2 supercrítico secagem. </li></ol> 4. Produção de Aerogels por CO2 supercrítico Secagem <ol><li> Coloque as amostras na mesma autoclave de alta pressão utilizado para a preparação do hidrogel (ver passo 2.3). </li><li> Encher o autoclave com etanol adicional (2-10% do volume do autoclave) para evitar a evaporação prematura do solvente a partir dos géis. imersão completa de gel no solvente não é necessária. </li><li> Selar o autoclave. Ligar o aquecimento autoclave. Defina a temperatura de trabalho autoclave a 323 K. pressurizar o autoclave com dióxido de carbono a 12 MPa usando um compressor ou bomba. </li><li> Periodicamente substituir o CO 2no interior da autoclave 10,11 com CO 2 fresco mantendo a pressão constante. 6-7 volumes de residência são necessárias ao longo de um período de 6 h. Consulte Gurikov et al. 7 para mais informações. </li><li> Lentamente despressurizar o autoclave a 0,2 MPa / min. </li><li> Abra o autoclave e recolher o aerogel. Armazenar o aerogel num exsicador ou um recipiente fechado. </li></ol>

<ol>
	<li>Kistler, S. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Coherent+expanded-aerogels.">Coherent expanded-aerogels.</a> J. Phys. Chem. 36 (1), 52-64 (1932).</li><li>Aegerter, M. A., Leventis, N., Koebel, M. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Aerogels Handbook. , (2011).</li><li>Raman, S. P., Gurikov, P., Smirnova, I. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Hybrid+alginate+based+aerogels+by+carbon+dioxide+induced+gelation:+Novel+technique+for+multiple+applications.">Hybrid alginate based aerogels by carbon dioxide induced gelation: Novel technique for multiple applications.</a> J. Supercrit. Fluids. 106, 23-33 (2015).</li><li>Draget, K. I., Skj&#229;k-Br&#230;k, G., Smidsr&#248;d, O. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Alginate+based+new+materials.">Alginate based new materials.</a> Int. J. Biol. Macromol. 21 (1), 47-55 (1997).</li><li>Garc&#237;a-Gonz&#225;lez, C. A., Alnaief, M., Smirnova, I. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Polysaccharide-based+aerogels-Promising+biodegradable+carriers+for+drug+delivery+systems.">Polysaccharide-based aerogels-Promising biodegradable carriers for drug delivery systems.</a> Carbohydr. Polym. 86 (4), 1425-1438 (2011).</li><li>Alnaief, M., Alzaitoun, M. A., Garc&#237;a-Gonz&#225;lez, C. A., Smirnova, I. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Preparation+of+biodegradable+nanoporous+microspherical+aerogel+based+on+alginate.">Preparation of biodegradable nanoporous microspherical aerogel based on alginate.</a> Carbohydr. Polym. 84 (3), 1011-1018 (2011).</li><li>Gurikov, P., Raman, S. P., Weinrich, D., Fricke, M., Smirnova, I. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+novel+approach+to+alginate+aerogels:+carbon+dioxide+induced+gelation.">A novel approach to alginate aerogels: carbon dioxide induced gelation.</a> RSC Adv. 5, 7812-7818 (2015).</li><li>Meyssami, B., Balaban, M. O., Teixeira, A. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Prediction+of+pH+in+model+systems+pressurized+with+carbon+dioxide.">Prediction of pH in model systems pressurized with carbon dioxide.</a> Biotechnol. Prog. 8 (2), 149-154 (1992).</li><li>Subrahmanyam, R., Gurikov, P., Dieringer, P., Sun, M., Smirnova, I. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=On+the+Road+to+Biopolymer+Aerogels-Dealing+with+the+Solvent.">On the Road to Biopolymer Aerogels-Dealing with the Solvent.</a> Gels. 1 (2), 291-313 (2015).</li><li>Garc&#237;a-Gonz&#225;lez, C. A., Camino-Rey, M. C., Alnaief, M., Zetzl, C., Smirnova, I. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Supercritical+drying+of+aerogels+using+CO2:+Effect+of+extraction+time+on+the+end+material+textural+properties.">Supercritical drying of aerogels using CO2: Effect of extraction time on the end material textural properties.</a> J. Supercrit. Fluids. 66, 297-306 (2012).</li><li>&#214;zbak&#305;r, Y., Erkey, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Experimental+and+theoretical+investigation+of+supercritical+drying+of+silica+alcogels.">Experimental and theoretical investigation of supercritical drying of silica alcogels.</a> J. Supercrit. Fluids. 98, 153-166 (2015).</li><li>Rudaz, C., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Aeropectin:+Fully+Biomass-Based+Mechanically+Strong+and+Thermal+Superinsulating+Aerogel.">Aeropectin: Fully Biomass-Based Mechanically Strong and Thermal Superinsulating Aerogel.</a> Biomacromolecules. 15 (6), 2188-2195 (2014).</li><li>Quraishi, S., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Novel+non-cytotoxic+alginate-lignin+hybrid+aerogels+as+scaffolds+for+tissue+engineering.">Novel non-cytotoxic alginate-lignin hybrid aerogels as scaffolds for tissue engineering.</a> J. Supercrit. Fluids. 105, 1-8 (2015).</li><li>Martins, M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Preparation+of+macroporous+alginate-based+aerogels+for+biomedical+applications.">Preparation of macroporous alginate-based aerogels for biomedical applications.</a> J. Supercrit. Fluids. 106, 152-159 (2015).</li><li>Davidovich-Pinhas, M., Bianco-Peled, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+quantitative+analysis+of+alginate+swelling.">A quantitative analysis of alginate swelling.</a> Carbohydr. Polym. 79 (4), 1020-1027 (2010).</li><li>Mallepally, R. R., Bernard, I., Marin, M. A., Ward, K. R., McHugh, M. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Superabsorbent+alginate+aerogels.">Superabsorbent alginate aerogels.</a> J. Supercrit. Fluids. 79, 202-208 (2013).</li><li>Porta, G. D., Del Gaudio, P., De Cicco, F., Aquino, R. P., Reverchon, E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Supercritical+Drying+of+Alginate+Beads+for+the+Development+of+Aerogel+Biomaterials:+Optimization+of+Process+Parameters+and+Exchange.">Supercritical Drying of Alginate Beads for the Development of Aerogel Biomaterials: Optimization of Process Parameters and Exchange.</a> Ind. Eng. Chem. Res. 52 (34), 12003-12009 (2013).</li><li>Brown, Z. K., Fryer, P. J., Norton, I. T., Bridson, R. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Drying+of+agar+gels+using+supercritical+carbon+dioxide.">Drying of agar gels using supercritical carbon dioxide.</a> J. Supercrit. Fluids. 54 (1), 89-95 (2010).</li><li>Betz, M., Garc&#237;a-Gonz&#225;lez, C. A., Subrahmanyam, R. P., Smirnova, I., Kulozik, U. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Preparation+of+novel+whey+protein-based+aerogels+as+drug+carriers+for+life+science+applications.">Preparation of novel whey protein-based aerogels as drug carriers for life science applications.</a> J. Supercrit. Fluids. 72, 111-119 (2012).</li><li>Antonyuk, S., Heinrich, S., Gurikov, P., Raman, S., Smirnova, I. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Influence+of+coating+and+wetting+on+the+mechanical+behaviour+of+highly+porous+cylindrical+aerogel+particles.">Influence of coating and wetting on the mechanical behaviour of highly porous cylindrical aerogel particles.</a> Powder Technol. 285, 34-43 (2015).</li></ol>

Os autores declaram que não têm interesses financeiros concorrentes.

Ao usar a técnica de gelificação induzida CO 2, pode-se eliminar a necessidade de substitutos químicos (por exemplo, ácido acético ou glucono-delta-lactona (GDL)) necessária para induzir a reticulação do biopolímero. As áreas de superfície dos aerogeles de pectina amidada estão situados nas gamas mais elevadas de 5 valores da literatura, no entanto, os volumes de poros são muito mais elevados do que os apresentados na literatura 5. Volumes de poros mais elevados também foram observados para os aerogéis de alginato preparadas pelo CO 2 gelificação induzida 7. No entanto, ele continua a ser verificado se a razão para este alto volume de poros (4-150 nm poros Faixa de tamanho) deve-se à técnica de gelificação ou uma propriedade inerente dos biopolímeros anteriormente não abordados na literatura. Pectina aerogéis têm sido relatados na literatura como possuindo propriedades 12 e aerogeles de alginato preparadas por esta técnica superinsulating também possuem uma condutividade térmica na gama superinsulating3,7. Por conseguinte, podem também prever-se os aerogéis de pectina amidada produzidos por esta técnica de possuir propriedades superinsulating. A taxa de despressurização na Secção Protocolo 2 é um passo importante na preparação de hidrogel. despressurização rápida pode conduzir a um aumento da macroporosidade dos géis. Este fenómeno pode ser aplicado para aplicações de engenharia de tecidos onde a macroporosidade do material com a interconexão é uma característica importante para o crescimento e proliferação de células 13,14. Além disso, o grau de reticulação na Secção Protocolo 1 desempenha um papel importante na propriedade sinérese e inchaço dos hidrogéis de pectina amidada. Isto é semelhante ao hidrogéis de alginato cujo comportamento de inchamento é influenciada pela concentração de agente de reticulação, bem 15. Assim aerogels feitas por pectina amidada também pode ser ajustado para possuir propriedade superabsorvente semelhantes aos relatados por aerogéis de alginato 16. &lt;p classe = &quot;jove_content&quot;&gt; Utilizando o CO 2 gelificação induzida considerando pectina amidada (ou alginato) como o sistema primário, ainda mais a diversidade podem ser incorporados nas aerogéis através da introdução de diferentes transversal agentes e combinações biopoliméricas ligando. Vários carbonatos de metal (por exemplo, zinco, níquel, cobalto, cobre, estrôncio, bário) poderia ser usado para reticulação 3, onde catiões pode ser libertado por uma descida do pH no meio aquoso com CO 2 pressurizado (3-5 MPa). No entanto, sais insolúveis de alguns desses cátions não podem formar dispersões estáveis ​​para as concentrações de biopolímeros mais baixos e podem estabelecer-se na parte inferior levando a géis não homogéneos. Este é um problema geral com o método de definição de gelificação interna, inclusive CO 2 gelificação induzida 3 e, assim, a usabilidade do técnica de um aplicativo deve ser avaliada caso a caso. Várias misturas preparadas utilizando bio solúvel em águapolímeros, tais como amido, carragenina, metil e carboximetilcelulose, goma de gelano, lignina, gelatina e outros; polímeros sintéticos solúveis em água tais como polietileno glicol (PEG), álcool polivinílico (PVA), Pluronic P-123 e outros; e solúvel em água precursores inorgânicos tais como silicato de sódio pode também ser misturado com pectina amidada para produzir aerogeles híbridas semelhantes a 2 alginato com propriedades ajustáveis. Como CO2 supercrítico de secagem (secagem SCCO 2) é um passo por excelência na produção aerogel, qualquer combinação de passos de pré-processamento, tais como a troca do solvente e secagem utilizando CO 2 ou de gelificação 17,18, troca de solvente e de secagem usando CO 2 7 poderia fornecer uma vantagem de processamento clara. A vantagem é vista como um processo integrado pote: onde dispersões de biopolímero pode ser convertido em aerogéis biopolímero utilizando CO2 como o meio de processamento principal num autoclave. Paracertas aplicações farmacêuticas, também se pode prever a execução de uma etapa quatro: gelificação, a troca do solvente, secagem supercrítica e ativo processo de componente de carga 5,19 em um único autoclave usando CO 2 como o meio de processamento. Pós-tratamento, tal como revestimento protector dos aerogéis carregadas com droga em certos casos é necessário para liberação do fármaco alvo 20. Para concluir, o presente trabalho demonstra a utilização de CO pressurizado 2 para gelificação de sistemas de pectina com base amidada. Além disso, está prevista a utilização de CO 2 pressurizado como um meio comum para precursor da conversão do produto para aplicações-alvo, em um único autoclave.

Os aerogéis são uma classe de materiais porosos, que podem ser preparados utilizando uma variedade de precursores que vão desde inorgânica (tais como sílica, titânia, zircónia e outros), sintéticos (tal como formaldeído de resorcinol, de poliuretano e outros) ou biopolimeros (polissacáridos, proteínas e outros ) 2. O que os diferencia dos materiais porosos convencionais é a sua capacidade de possuir simultaneamente todas as três características; ou seja, a área de superfície elevada, ultra-baixa densidade e distribuição de tamanho de poro mesoporosa (ou seja, tamanhos de poro de 2-50 nM). Com características acima mencionadas, os aerogéis são amplamente aplicados nas áreas de aplicações de isolamento, biomedicina, catálise, adsorção e absorção, produtos farmacêuticos e nutracêuticos 2. Tendo em conta as possibilidades acima, a produção de sistemas de gel de biopolímero e sua posterior transformação para aerogels abre uma infinidade de oportunidades para com alto valor adicionado com base biomateriais. Este esforço é retomado neste estudo utilizando pectina amidada como um exemplo. Os aerogéis são tipicamente produzidos pela técnica de sol-gel. Os geles são sistemas que consistem de líquido aprisionado numa matriz e pode ser preparada por ligação covalente, iónica, pH induzida, transversal térmica ou crio ligando 3. Para este sistema específico, nós utilizamos reticulação iónico, isto é, um catião bivalente (por exemplo, cálcio) para reticular cadeias biopolimêricos juntos. Para realizar a reticulação iónica controlável de biopolímeros tais como pectina ou alginato amidado, pode-se utilizar o método de difusão ou método de configuração interna 4. No método de difusão, a gelificação ocorre em primeiro lugar na camada externa, seguido por propagação de difusão, como os catiões de difundir a partir da solução externa a uma pectina amidada ou gotícula de alginato ou camada 4. No método de configuração interna, a forma insolúvel de o agente de reticulação está homogeneamente disperso no solutio biopolímeron e cátions são liberados, iniciando uma 4,5,6 alteração do pH. No entanto, ambas as técnicas de enfrentar um problema em relação à homogeneidade do gel final, quando produzido em laje ou forma monolítica. Este trabalho demonstra o uso de CO 2 alta pressão (5 MPa) para a produção de hidrogéis de pectina amidada construção ainda em trabalhos anteriores sobre géis de alginato 3,7. Em resumo, é uma técnica de gelificação configuração interna que utiliza CO pressurizado 2 para reduzir o pH em vez de ácidos fracos para produzir géis homogéneos. Com um aumento na pressão, a solubilidade do dióxido de carbono em aumentos de água acompanhadas por uma diminuição do pH a 3,0 8. Isto faz com que o carbonato de cálcio para solubilizar, libertar os iões de cálcio. Os iões de cálcio reticular com o biopolímero pectina amidada para produzir hidrogeles. Geles homogéneos estáveis ​​para baixo a concentrações muito baixas de biopolímero (0,05% em peso) pode ser produzido utilizando esta técnica 7. como Gelatde iões tem lugar num meio aquoso, a troca de solvente para um solvente orgânico é necessário para uma lacuna devido a miscibilidade no sistema de CO 2 / água. Tipicamente álcoois de baixo peso molecular (metanol / etanol / isopropanol) e cetonas (acetona) pode ser usado para o processo de troca de solvente. No entanto, imersão directa em um banho com etanol puro ou outros solventes orgânicos conduz a retracção irreversível significativa. Para evitar este inconveniente, a troca do solvente por etapas é realizada 5,9. Quando a concentração de solvente no interior do gel atinge&gt; 98%, o solvente orgânico é seco com CO2 supercrítico (12 MPa) deixando para trás um aerogel.

<table border="0" cellpadding="0" cellspacing="0" width="1321">
	<tbody>
		<tr height="26">
			<td height="26" style="height:26px;width:289px;">Equipment</td>
			<td style="width:196px;"></td>
			<td style="width:240px;"></td>
			<td style="width:596px;"></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Ultraturrax homogenizer</td>
			<td>IKA, Germany</td>
			<td>T 25 Digital</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Polypropylene molds</td>
			<td>TH. Geyer, Germany</td>
			<td>9,033,201</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">High pressure autoclave&#160;</td>
			<td>Ernst Haage, Germany</td>
			<td>custom made</td>
			<td>Setup constuction done in-house</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Compressor</td>
			<td>Andreas Hofer</td>
			<td>MKZ 185-40</td>
			<td>Setup constuction done in-house</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Nitrogen adsorption</td>
			<td>Quantachrome</td>
			<td>Nova 4000e</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Density meter</td>
			<td>Anton Paar</td>
			<td>DMA 4000</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Name</td>
			<td>Company</td>
			<td>Catalog Number</td>
			<td>Comments</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:289px;">Chemicals</td>
			<td style="width:196px;"></td>
			<td style="width:240px;"></td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Amidated pectin</td>
			<td>Herbstreith and Fox, Germany</td>
			<td>CU 025</td>
			<td>CAS # 56645-02-4; provided by company for research purposes</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Sodium Hydroxide</td>
			<td>Sigma Aldrich, Germany</td>
			<td style="width:240px;">S8045</td>
			<td>CAS # 1310-73-2; required only in case the pectin solution needs to be neutralized to pH 6.5-7.5</td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;">Calcium carbonate</td>
			<td>Magnesia GmbH, Germany</td>
			<td style="width:240px;">4421 Calcium carbonat, leicht, pr&#228;zipitiert, EP, E170</td>
			<td>CAS # 471-34-1</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Ethanol, 99.8 %</td>
			<td>Sigma Aldrich, Germany</td>
			<td>32205</td>
			<td>CAS # 64-17-5</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Carbon dioxide, 99.9 %</td>
			<td>AGA Gas GmbH, Germany</td>
			<td></td>
			<td>CAS # 124-38-9; in-house tank available (3 ton)</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Deionised Water</td>
			<td></td>
			<td></td>
			<td>CAS # 7732-18-5;&#160; available in-house (6.4-7.0 pH)</td>
		</tr>
	</tbody>
</table>

preparation of biopolymer aerogels using green solvents

Although the first reports on aerogels made by Kistler1 in the 1930s dealt with aerogels from both inorganic oxides (silica and others) and biopolymers (gelatin, agar, cellulose), only recently have biomasses been recognized as an abundant source of chemically diverse macromolecules for functional aerogel materials. Biopolymer aerogels (pectin, alginate, chitosan, cellulose, etc.) exhibit both specific inheritable functions of starting biopolymers and distinctive features of aerogels (80-99% porosity and specific surface up to 800 m2/g). This synergy of properties makes biopolymer aerogels promising candidates for a wide gamut of applications such as thermal insulation, tissue engineering and regenerative medicine, drug delivery systems, functional foods, catalysts, adsorbents and sensors. This work demonstrates the use of pressurized carbon dioxide (5 MPa) for the ionic cross linking of amidated pectin into hydrogels. Initially a biopolymer/salt dispersion is prepared in water. Under pressurized CO2 conditions, the pH of the biopolymer solution is lowered to 3 which releases the crosslinking cations from the salt to bind with the biopolymer yielding hydrogels. Solvent exchange to ethanol and further supercritical CO2 drying (10 - 12 MPa) yield aerogels. Obtained aerogels are ultra-porous with low density (as low as 0.02 g/cm3), high specific surface area (350 - 500 m2/g) and pore volume (3 - 7 cm3/g for pore sizes less than 150 nm).

Os hidrogéis típicos obtidos após o passo de gelificação, com maior grau de reticulação (q = 2) (conforme indicado na secção Protocolo 2) são mostrados na Figura 1. As amostras à esquerda (amostra A e B) são a 2% em peso e 1% em peso geles de pectina obtidas pelo CO 2 induziram a gelatinização. Ao diminuir a concentração de biopolímero (0,5% em peso ou inferior), os géis se tornar transparente (Amostra C). Nova redução na concentração de biopolímeros (0,25%) também produz hidrogéis estáveis ​​(amostra D), mas esses géis são muito frágeis e podem quebrar durante o manuseio. As bolhas observadas no interior dos hidrogeles são criados durante a despressurização, quando o CO 2 dissolvido sai do sistema de água de gel devido à diminuição da solubilidade de CO2. As características de pectina amidada de aerogel são apresentados na Tabela 1. Os aerogéis obtidos são ultra-poroso, com baixa den<html> sidade (tão baixos como 0,013 g / cm 3) medida como a razão entre a massa do aerogel e do seu volume. A área superficial é medida por adsorção de azoto. Para aerogéis de pectina, que produziu uma área superficial específica entre 350 - 500 m 2 / g. O volume de poros de tamanhos de poro na gama de 4-150 nm é medida pelo modelo Kelvin de enchimento de poros usando azoto (método BJH). O volume de poro para os aerogéis de pectina amidada era entre 3-7 cm3 / g para os tamanhos de poro entre 4 e 150 nm. <img alt="figura 1" src="/files/ftp_upload/54116/54116fig1.jpg" /> Figura 1. hidrogéis pectina amidada com maior grau de reticulação (q = 2) superior esquerda: 2% em peso (amostra A);. superior direito: 1% (Amostra B); canto inferior esquerdo: 0,5% (Amostra C); canto inferior direito: 0,25% (Amostra D). Géis tornar transparente com a diminuição da concentração de biopolímeros. As bolhas são produzidas durante a co 2 despressurização.https://www.jove.com/files/ftp_upload/54116/54116fig1large.jpg &quot;target =&quot; _ blank &quot;&gt; Clique aqui para ver uma versão maior desta figura. <table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always"><tbody><tr><td> Concentração de pectina [% em peso] </td><td> Cross-linking grau q </td><td> Densidade aparente [g / cm3] </td><td> Área de superfície específica [m2 / g] </td><td> Volume de poro específico [cm3 / g] </td><td> Tamanho de poro médio (diâmetro) [nm] </td></tr><tr><td> 2,00 </td><td> 1 </td><td> 0,081 </td><td> 502 </td><td> 4.1 </td><td> 14 </td></tr><tr><td> 1.00 </td><td> 1 </td><td> 0,044 </td><td> 491 </td><td> 7.1 </td><td> 27 </td></tr><tr><td> 0.50 </td><td> 1 </td><td> 0,035 </td><td> 357 </td><td> 3.8 </td><td> 27 </td></tr><tr><td> 0,25 </td><td> 1 </td&gt; <td> 0,013 </td><td> 335 </td><td> 4.9 </td><td> 41 </td></tr><tr><td> 2,00 </td><td> 2 </td><td> 0,069 </td><td> 447 </td><td> 3.1 </td><td> 13 </td></tr><tr><td> 1.00 </td><td> 2 </td><td> 0,048 </td><td> 441 </td><td> 3.6 </td><td> 26 </td></tr><tr><td> 0.50 </td><td> 2 </td><td> 0,030 </td><td> 429 </td><td> 5.8 </td><td> 25 </td></tr><tr><td> 0,25 </td><td> 2 </td><td> 0,017 </td><td> 347 </td><td> 5 </td><td> 24 </td></tr></tbody></table> Tabela 1. Características dos aerogéis de pectina amidada.

Watch this Scientific Journal Video about Preparation of Biopolymer Aerogels Using Green Solvents at JoVE.com

Preparation of Biopolymer Aerogels Using Green Solvents

A new way for the production of biopolymer-based aerogels by carbon dioxide (CO2) induced gelation is shown. The technique utilizes pressurized carbon dioxide (5 MPa) for the production of biopolymer hydrogels and supercritical CO2 (12 MPa) to convert gels into aerogels. The only solvents needed besides CO2 are water and ethanol.

Preparação de Biopolymer Aerogels utilizando solventes verdes

Although the first reports on aerogels made by Kistler1 in the 1930s dealt with aerogels from both inorganic oxides (silica and others) and biopolymers ...

preparation-of-biopolymer-aerogels-using-green-solvents

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17.5K visualizações.  Hamburg University of Technology. A new way for the production of biopolymer-based aerogels by carbon dioxide (CO2) induced gelation is shown. The technique utilizes pressurized carbon dioxide (5 MPa) for the production of biopolymer hydrogels and supercritical CO2 (12 MPa) to convert gels into aerogels. The only solvents needed besides CO2 are water and ethanol.

Vídeo: Preparation of Biopolymer Aerogels Using Green Solvents

Exploring the Radical Nature of a Carbon Surface by Electron Paramagnetic Resonance and a Calibrated Gas Flow

While the first Electron Paramagnetic Resonance (EPR) studies regarding the effects of oxidation on the structure and stability of carbon radicals date back to the early 1980s the focus of these early papers primarily characterized the changes to the structures under extremely harsh conditions (pH or temperature)1-3. It is also known that paramagnetic molecular oxygen undergoes a Heisenberg spin exchange interaction with stable radicals that extremely broadens the EPR signal4-6. Recently, we reported interesting results where this interaction of molecular oxygen with a certain part of the existing stable radical structure can be reversibly affected simply by flowing a diamagnetic gas through the carbon samples at STP7. As flows of He, CO2, and N2 had a similar effect these interactions occur at the surface area of the macropore system.
This manuscript highlights the experimental techniques, work-up, and analysis towards affecting the existing stable radical nature in the carbon structures. It is hoped that it will help towards further development and understanding of these interactions in the community at large.

Stable radicals that are present in carbon substrates interact with paramagnetic oxygen through a Heisenberg spin exchange. This interaction can be significantly reduced under STP conditions by flowing a diamagnetic gas over the carbon system. This manuscript describes a simple method to characterize the nature of those radicals.

Explorando a Natureza Radical de uma superfície de carbono por ressonância paramagnética eletrônica e um fluxo de gás Calibrado

While the first Electron Paramagnetic Resonance (EPR) studies regarding the effects of oxidation on the structure and stability of carbon radicals date ...

Química

Real-time Monitoring of Reactions Performed Using Continuous-flow Processing: The Preparation of 3-Acetylcoumarin as an Example

By using inline monitoring, it is possible to optimize reactions performed using continuous-flow processing in a simple and rapid way. It is also possible to ensure consistent product quality over time using this technique. We here show how to interface a commercially available flow unit with a Raman spectrometer. The Raman flow cell is placed after the back-pressure regulator, meaning that it can be operated at atmospheric pressure. In addition, the fact that the product stream passes through a length of tubing before entering the flow cell means that the material is at RT. It is important that the spectra are acquired under isothermal conditions since Raman signal intensity is temperature dependent. Having assembled the apparatus, we then show how to monitor a chemical reaction, the piperidine-catalyzed synthesis of 3-acetylcoumarin from salicylaldehyde and ethyl acetoacetate being used as an example. The reaction can be performed over a range of flow rates and temperatures, the in-situ monitoring tool being used to optimize conditions simply and easily.

Real-time monitoring allows for fast optimization of reactions performed using continuous-flow processing. Here the preparation of 3-acetylcoumarin is used as an example. The apparatus for performing in-situ Raman monitoring is described, as are the steps required to optimize the reaction.

Monitoramento em tempo real de Reações realizada utilizando processamento de fluxo contínuo: A Preparação de 3-Acetylcoumarin como Exemplo

By using inline monitoring, it is possible to optimize reactions performed using continuous-flow processing in a simple and rapid way. It is also possible ...

Synthetic Methodology for Asymmetric Ferrocene Derived Bio-conjugate Systems via Solid Phase Resin-based Methodology

Early detection is a key to successful treatment of most diseases, and is particularly imperative for the diagnosis and treatment of many types of cancer. The most common techniques utilized are imaging modalities such as Magnetic Resonance Imaging (MRI), Positron Emission Topography (PET), and Computed Topography (CT) and are optimal for understanding the physical structure of the disease but can only be performed once every four to six weeks due to the use of imaging agents and overall cost. With this in mind, the development of &#8220;point of care&#8221; techniques, such as biosensors, which evaluate the stage of disease and/or efficacy of treatment in the clinician&#8217;s office and do so in a timely manner, would revolutionize treatment protocols.1 As a means to exploring ferrocene based biosensors for the detection of biologically relevant molecules2, methods were developed to produce ferrocene-biotin bio-conjugates described herein. This report will focus on a biotin-ferrocene-cysteine system that can be immobilized on a gold surface.

The synthesis of asymmetric species of ferrocene is challenging using solution techniques. This report focuses on the methods carried out to produce a ferrocene-biotin bioconjugate using facile and clean reactions accomplished via solid-phase synthesis. Incorporation of a thiolate moiety is shown to impart the ability for immobilization on gold surfaces.

Metodologia sintética para Asymmetric Ferroceno Derivados Sistemas Bio-conjugadas via Metodologia base de resina em Fase Sólida

Early detection is a key to successful treatment of most diseases, and is particularly imperative for the diagnosis and treatment of many types of cancer. ...

Characterization, Quantification and Compound-specific Isotopic Analysis of Pyrogenic Carbon Using Benzene Polycarboxylic Acids (BPCA)

Fire-derived, pyrogenic carbon (PyC), sometimes called black carbon (BC), is the carbonaceous solid residue of biomass and fossil fuel combustion, such as char and soot. PyC is ubiquitous in the environment due to its long persistence, and its abundance might even increase with the projected increase in global wildfire activity and the continued burning of fossil fuel. PyC is also increasingly produced from the industrial pyrolysis of organic wastes, which yields charred soil amendments (biochar). Moreover, the emergence of nanotechnology may also result in the release of PyC-like compounds to the environment. It is thus a high priority to reliably detect, characterize and quantify these charred materials in order to investigate their environmental properties and to understand their role in the carbon cycle.
Here, we present the benzene polycarboxylic acid (BPCA) method, which allows the simultaneous assessment of PyC&#39;s characteristics, quantity and isotopic composition (13C and 14C) on a molecular level. The method is applicable to a very wide range of environmental sample materials and detects PyC over a broad range of the combustion continuum, i.e., it is sensitive to slightly charred biomass as well as high temperature chars and soot. The BPCA protocol presented here is simple to employ, highly reproducible, as well as easily extendable and modifiable to specific requirements. It thus provides a versatile tool for the investigation of PyC in various disciplines, ranging from archeology and environmental forensics to biochar and carbon cycling research.

Characterization, Quantification and Compound-specific Isotopic Analysis of Pyrogenic Carbon Using Benzene Polycarboxylic Acids BPCA

We present the benzene polycarboxylic acid (BPCA) method for assessing pyrogenic carbon (PyC) in the environment. The compound-specific approach uniquely provides simultaneous information about the characteristics, quantity and isotopic composition (13C and 14C) of PyC.

Caracterização, quantificação e específicos do Composto isotópica Análise de Pirogênica carbono, usando Benzeno policarboxílicos Acids (BPCA)

Fire-derived, pyrogenic carbon (PyC), sometimes called black carbon (BC), is the carbonaceous solid residue of biomass and fossil fuel combustion, such as ...

Green and Low-cost Production of Thermally Stable and Carboxylated Cellulose Nanocrystals and Nanofibrils Using Highly Recyclable Dicarboxylic Acids

Here we demonstrate potentially low cost and green productions of high thermally stable and carboxylated cellulose nanocrystals (CNCs) and nanofibrils (CNF) from bleached eucalyptus pulp (BEP) and unbleached mixed hardwood kraft pulp (UMHP) fibers using highly recyclable dicarboxylic solid acids. Typical operating conditions were acid concentrations of 50 - 70 wt% at 100 &#176;C for 60 min and 120 &#176;C (no boiling at atmospheric pressure) for 120 min, for BEP and UMHP, respectively. The resultant CNCs have a higher thermal degradation temperature than their corresponding feed fibers and carboxylic acid group content from 0.2 - 0.4 mmol/g. The low strength (high pKa of 1.0 - 3.0) of organic acids also resulted in CNCs with both longer lengths of approximately 239 - 336 nm and higher crystallinity than CNCs produced using mineral acids. Cellulose loss to sugar was minimal. Fibrous cellulosic solid residue (FCSR) from the dicarboxylic acid hydrolysis was used to produce carboxylated CNFs through subsequent mechanical fibrillation with low energy input.

Here we demonstrate a novel method for green and sustainable productions of highly thermally stable and carboxylated cellulose nanocrystals (CNC) and nanofibrils (CNF) using highly recyclable solid dicarboxylic acids.

Produção-Baixo custo de verde e de estabilidade térmica e carboxilado Celulose Nanocristais e nanofibrilas Usando altamente reciclável Dicarboxílicos Acids

Here we demonstrate potentially low cost and green productions of high thermally stable and carboxylated cellulose nanocrystals (CNCs) and nanofibrils ...

Preparation and Evaluation of 99mTc-labeled Tridentate Chelates for Pre-targeting Using Bioorthogonal Chemistry

Pre-targeting combined with bioorthogonal chemistry is emerging as an effective way to create new radiopharmaceuticals. Of the methods available, the inverse electron demand Diels-Alder (IEDDA) cycloaddition between a radiolabeled tetrazines and trans-cyclooctene (TCO) linked to a biomolecule has proven to be a highly effective bioorthogonal approach to imaging specific biological targets. Despite the fact that technetium-99m remains the most widely used isotope in diagnostic nuclear medicine, there is a scarcity of methods for preparing 99mTc-labeled tetrazines. Herein we report the preparation of a family of tridentate-chelate-tetrazine derivatives and their Tc(I) complexes. These hitherto unknown compounds were radiolabeled with 99mTc using a microwave-assisted method in 31% to 83% radiochemical yield. The products are stable in saline and PBS and react rapidly with TCO derivatives in vitro. Their in vivo pre-targeting abilities were demonstrated using a TCO-bisphosphonate (TCO-BP) derivative that localizes to regions of active bone metabolism or injury. In murine studies, the 99mTc-tetrazines showed high activity concentrations in knees and shoulder joints, which was not observed when experiments were performed in the absence of TCO-BP. The overall uptake in non-target organs and pharmacokinetics varied greatly depending on the nature of the linker and polarity of the chelate.

Preparation and Evaluation of 99mTc-labeled Tridentate Chelates for Pre-targeting Using Bioorthogonal Chemistry

Here, we describe a protocol for radiolabeling and in vivo testing of tridentate 99mTc(I) chelate-tetrazine derivatives for pre-targeting and bioorthogonal chemistry.

Preparação e Avaliação de<sup&gt; 99m</sup&gt; Tc-rotulados tridentadas Quelatos de Pré-alvo Usando Bioorthogonal Química

Pre-targeting combined with bioorthogonal chemistry is emerging as an effective way to create new radiopharmaceuticals. Of the methods available, the ...

Fabrication and Testing of Catalytic Aerogels Prepared Via Rapid Supercritical Extraction

Protocols for preparing and testing catalytic aerogels by incorporating metal species into silica and alumina aerogel platforms are presented. Three preparation methods are described: (a) the incorporation of metal salts into silica or alumina wet gels using an impregnation method; (b) the incorporation of metal salts into alumina wet gels using a co-precursor method; and (c) the addition of metal nanoparticles directly into a silica aerogel precursor mixture. The methods utilize a hydraulic hot press, which allows for rapid (&#60;6 h) supercritical extraction and results in aerogels of low density (0.10 g/mL) and high surface area (200-800 m2/g). While the work presented here focuses on the use of copper salts and copper nanoparticles, the approach can be implemented using other metal salts and nanoparticles. A protocol for testing the three-way catalytic ability of these aerogels for automotive pollution mitigation is also presented. This technique uses custom-built equipment, the Union Catalytic Testbed (UCAT), in which a simulated exhaust mixture is passed over an aerogel sample at a controlled temperature and flow rate. The system is capable of measuring the ability of the catalytic aerogels, under both oxidizing and reducing conditions, to convert CO, NO and unburned hydrocarbons (HCs) to less harmful species (CO2, H2O and N2). Example catalytic results are presented for the aerogels described.

Here we present protocols for preparing and testing catalytic aerogels by incorporating metal species into silica and alumina aerogel platforms. Methods for preparing materials using copper salts and copper-containing nanoparticles are featured. Catalytic testing protocols demonstrate the effectiveness of these aerogels for three-way catalysis applications.

Fabricação e teste de catalítico Aerogels preparado através da rápida extração supercrítica

Protocols for preparing and testing catalytic aerogels by incorporating metal species into silica and alumina aerogel platforms are presented. Three ...

Preparation of Functional Silica Using a Bioinspired Method

The goal of the protocols described herein is to synthesize bioinspired silica materials, perform enzyme encapsulation therein, and partially or totally purify the same by acid elution. By combining sodium silicate with a polyfunctional bioinspired additive, silica is rapidly formed at ambient conditions upon neutralization. 
The effect of neutralization rate and biomolecule addition point on silica yield are investigated, and biomolecule immobilization efficiency is reported for varying addition point. In contrast to other porous silica synthesis methods, it is shown that the mild conditions required for bioinspired silica synthesis are fully compatible with the encapsulation of delicate biomolecules. Additionally, mild conditions are used across all synthesis and modification steps, making bioinspired silica a promising target for the scale-up and commercialization as both a bare material and active support medium.
The synthesis is shown to be highly sensitive to conditions, i.e., the neutralization rate and final synthesis pH, however tight control over these parameters is demonstrated through the use of auto titration methods, leading to high reproducibility in reaction progression pathway and yield. 
Therefore, bioinspired silica is an excellent active material support choice, showing versatility towards many current applications, not limited to those demonstrated here, and potency in future applications.

Here, we present a protocol to synthesize bioinspired silica materials and immobilize enzymes therein. Silica is synthesized by combining sodium silicate and an amine &#39;additive&#39;, which neutralize at a controlled rate. Material properties and function can be altered either by in situ enzyme immobilization or post-synthetic acid elution of encapsulated additives.

Preparação de sílica funcional usando um método Bioinspirada

The goal of the protocols described herein is to synthesize bioinspired silica materials, perform enzyme encapsulation therein, and partially or totally ...

A Rapid Synthesis Method for Au, Pd, and Pt Aerogels Via Direct Solution-Based Reduction

Here, a method to synthesize gold, palladium, and platinum aerogels via a rapid, direct solution-based reduction is presented. The combination of various precursor noble metal ions with reducing agents in a 1:1 (v/v) ratio results in the formation of metal gels within seconds to minutes compared to much longer synthesis times for other techniques such as sol-gel. Conducting the reduction step in a microcentrifuge tube or small volume conical tube facilitates a proposed nucleation, growth, densification, fusion, equilibration model for gel formation, with final gel geometry smaller than the initial reaction volume. This method takes advantage of the vigorous hydrogen gas evolution as a by-product of the reduction step, and as a consequence of reagent concentrations. The solvent accessible specific surface area is determined with both electrochemical impedance spectroscopy and cyclic voltammetry. After rinsing and freeze drying, the resulting aerogel structure is examined with scanning electron microscopy, X-ray diffractometry, and nitrogen gas adsorption. The synthesis method and characterization techniques result in a close correspondence of aerogel ligament sizes. This synthesis method for noble metal aerogels demonstrates that high specific surface area monoliths may be achieved with a rapid and direct reduction approach.

A rapid, direct solution-based reduction synthesis method to obtain Au, Pd, and Pt aerogels is presented.

Um método de síntese rápida para Au, Pd e Pt Aerogels através de redução direta baseada em solução

Here, a method to synthesize gold, palladium, and platinum aerogels via a rapid, direct solution-based reduction is presented. The combination of various ...

Achieving Moderate Pressures in Sealed Vessels Using Dry Ice As a Solid CO2 Source

Herein is presented a general strategy to perform reactions under mild to moderate CO2 pressures with dry ice. This technique obviates the need for specialized equipment to achieve modest pressures, and can even be used to achieve higher pressures in more specialized equipment and sturdier reaction vessels. At the end of the reaction, the vials can be easily depressurized by opening at room temperature. In the present example CO2 serves as both a putative directing group as well as a way to passivate amine substrates, thereby preventing oxidation during the organometallic reaction. In addition to being easily added, the directing group is also removed under vacuum, obviating the need for extensive purification to remove the directing group. This strategy allows the facile &#947;-C(sp3)-H arylation of aliphatic amines and has the potential to be applied to a variety of other amine-based reactions.

Achieving Moderate Pressures in Sealed Vessels Using Dry Ice As a Solid CO2 Source

Here we present a protocol for performing reactions in simple reaction vessels under low-to-moderate pressures of CO2. The reactions can be performed in a variety of vessels simply by administering the carbon dioxide in the form of dry ice, without the need for costly or elaborate equipment or set-ups.

Atingir pressões moderadas em vasos selados usando gelo seco como uma sólido CO2 fonte

Herein is presented a general strategy to perform reactions under mild to moderate CO2 pressures with dry ice. This technique obviates the need for ...

Preparação de Biopolymer Aerogels utilizando solventes verdes

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