The authors would like to thank Dr. John Harbell for his scientific support and time dedicated to the EIT project. The authors also would like to thank Beiersdorf AG (Germany), IIVS (USA), Mary Kay Inc. (USA), Avon Products Inc. (USA), Procter &#38; Gamble/Cosmital (Switzerland), Laboratoire Pierre Fabre (France), Harlan Laboratories (United Kingdom), and LVMH Parfume (France) for participation in Multi-center International Pre-Validation and Validation Studies of the Eye Irritation Test15.

<ol>
	<li>National Toxicology Program (NTP) Interagency Center for the Evaluation of Alternative Toxicological Methods (NICEATM). <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Request+for+Ocular+Irritancy+Test+Data+From+Human,+Rabbit,+and+In+Vitro+Studies+Using+Standardized+Testing+Methods.">Request for Ocular Irritancy Test Data From Human, Rabbit, and In Vitro Studies Using Standardized Testing Methods.</a> Federal Register. 72 (109), 31582-31583 (2007).</li><li>. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Regulation+(EC)+No+1907/2006+of+the+European+Parliament+and+of+the+Council+of+18+December+2006+concerning+the+Registration,+Evaluation,+Authorisation+and+Restriction+of+Chemicals+(REACH),+establishing+a+European+Chemicals+Agency,+amending+Directive+1999/45/EC+and+repealing+Council+Regulation+(EEC)+No+793/93+and+Commission+Regulation+(EC)+No+1488/94+as+well+as+Council+Directive+76/769/EEC+and+Commission+Directives+91/155/EEC,+93/67/EEC,+93/105/EC+and+2000/21/EC.">Regulation (EC) No 1907/2006 of the European Parliament and of the Council of 18 December 2006 concerning the Registration, Evaluation, Authorisation and Restriction of Chemicals (REACH), establishing a European Chemicals Agency, amending Directive 1999/45/EC and repealing Council Regulation (EEC) No 793/93 and Commission Regulation (EC) No 1488/94 as well as Council Directive 76/769/EEC and Commission Directives 91/155/EEC, 93/67/EEC, 93/105/EC and 2000/21/EC.</a> OJ. L396 (49), 1-849 (2006).</li><li>. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Globally Harmonized System of Classification and Labelling of Chemicals (GHS). , (2013).</li><li>Draize, J. H., Woodard, G., Calvery, H. O. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Methods+for+the+Study+of+Irritation+and+Toxicity+of+Substances+Applied+Topically+to+the+Skin+and+Mucous+Membranes.">Methods for the Study of Irritation and Toxicity of Substances Applied Topically to the Skin and Mucous Membranes.</a> J Pharmacol Exp Ther November. 82, 377-390 (1944).</li><li>Adriaens, E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Retrospective+analysis+of+the+Draize+test+for+serious+eye+damage/eye+irritation:+importance+of+understanding+the+in+vivo+endpoints+under+UN+GHS/EU+CLP+for+the+development+and+evaluation+of+in+vitro+test+methods.">Retrospective analysis of the Draize test for serious eye damage/eye irritation: importance of understanding the in vivo endpoints under UN GHS/EU CLP for the development and evaluation of in vitro test methods.</a> Arch tox. 88, 701-723 (2014).</li><li>Balls, M., Botham, P. A., Bruner, L. H., Spielmann, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+EC/HO+international+validation+study+on+alternatives+to+the+Draize+eye+irritation+test.">The EC/HO international validation study on alternatives to the Draize eye irritation test.</a> Toxicol in Vitro. 9, 871-929 (1995).</li><li>Curren, R. D., Harbell, J. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Ocular+safety:+a+silent+(in+vitro)+success+story.">Ocular safety: a silent (in vitro) success story.</a> Altern Lab Anim. 30, 69-74 (2002).</li><li>Wilhelmus, K. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+Draize+Eye+Test.">The Draize Eye Test.</a> Survey of Ophthalmology. 45, 493-515 (2001).</li><li>Curren, R. D., Harbell, J. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=In+vitro+alternatives+for+ocular+irritation.">In vitro alternatives for ocular irritation.</a> Environ health persp. 106, 485-492 (1998).</li><li>McCain, N. E., Binetti, R. R., Gettings, S. D., Jones, B. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Assessment+of+ocular+irritation+ranges+of+market-leading+cosmetic+and+personal-care+products+using+an+in+vitro+tissue+equivalent.">Assessment of ocular irritation ranges of market-leading cosmetic and personal-care products using an in vitro tissue equivalent.</a> Toxicologist. 66, 243 (2002).</li><li>Niranjan, P., Dang, A. H., January, B. G., Gomez, C., Harbell, J. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Use+of+the+EpiOcular+assay+for+preclinical+qualification+of+formulas+for+human+clinical+studies.">Use of the EpiOcular assay for preclinical qualification of formulas for human clinical studies.</a> Toxicologist. 96, 249 (2007).</li><li>Yin, X. J. <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+ocular+irritation+potential+of+surfactants-based+formulations+at+different+concentrations+using+the+EpiOcular+model.">Prediction of ocular irritation potential of surfactants-based formulations at different concentrations using the EpiOcular model.</a> Toxicologist. 108, 378 (2009).</li><li>Harbell, J., Curren, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=In+vitro+methods+for+the+prediction+of+ocular+and+dermal+toxicity.">In vitro methods for the prediction of ocular and dermal toxicity.</a> Handbook of Toxicology. , (2001).</li><li>Kaluzhny, Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Development+of+the+EpiOcular(TM)+eye+irritation+test+for+hazard+identification+and+labelling+of+eye+irritating+chemicals+in+response+to+the+requirements+of+the+EU+cosmetics+directive+and+REACH+legislation.">Development of the EpiOcular(TM) eye irritation test for hazard identification and labelling of eye irritating chemicals in response to the requirements of the EU cosmetics directive and REACH legislation.</a> Altern Lab Anim. 39, 339-364 (2011).</li><li>Pfannenbecker, U. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cosmetics+Europe+Multi-Laboratory+Pre-Validation+of+the+EpiOcular+Reconstituted+Human+Tissue+Test+Method+for+the+Prediction+of+Eye+Irritation.">Cosmetics Europe Multi-Laboratory Pre-Validation of the EpiOcular Reconstituted Human Tissue Test Method for the Prediction of Eye Irritation.</a> Toxicol in vitro. , (2013).</li><li>MatTek Corporation. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> EpiOcular™ Eye Irritation Test (OCL-200-EIT) for the prediction of acute ocular irritation of chemicals for use with Reconstructed Human EpiOcular Model (OCL-200-EIT). Protocol#MK-24-007-0055. , (2014).</li><li>Kaluzhny, Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=EpiOcular+Eye+Irritation+Test+(EIT)+for+Hazard+Identification+and+Labeling+of+Eye+Irritating+Chemicals:+Protocol+Optimization+for+Solid+Materials+and+Extended+Shipment+Times.">EpiOcular Eye Irritation Test (EIT) for Hazard Identification and Labeling of Eye Irritating Chemicals: Protocol Optimization for Solid Materials and Extended Shipment Times.</a> Altern Lab Anim. 43 (2), 101-127 (2015).</li><li>Kolle, S. N., Kandarova, H., Wareing, B., van Ravenzwaay, B., Landsiedel, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=In-house+validation+of+the+EpiOcular(TM)+eye+irritation+test+and+its+combination+with+the+bovine+corneal+opacity+and+permeability+test+for+the+assessment+of+ocular+irritation.">In-house validation of the EpiOcular(TM) eye irritation test and its combination with the bovine corneal opacity and permeability test for the assessment of ocular irritation.</a> Altern Lab Anim. 39, 365-387 (2011).</li><li>. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Reconstructed+Human+Cornea-like+Epithelium+(RhCE)+Test+Method+for+Identifying+Chemicals+Not+Requiring+Classification+and+Labelling+for+Eye+Irritation+or+Serious+Eye+Damage.+Draft+proposal+for+a+new+test+guideline..">Reconstructed Human Cornea-like Epithelium (RhCE) Test Method for Identifying Chemicals Not Requiring Classification and Labelling for Eye Irritation or Serious Eye Damage. Draft proposal for a new test guideline..</a> OECD Guideline for the Testing of Chemicals. , (2014).</li><li>Blazka, M. E., Harbell, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Evaluating+the+ocular+irritation+potential+of+54+test+articles+using+the+EpiOcular+Human+tissue+Construct+Model.">Evaluating the ocular irritation potential of 54 test articles using the EpiOcular Human tissue Construct Model.</a> Toxicol. In Vitro. , (2003).</li><li>Kandarova, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+EpiDerm+Test+Protocol+for+the+Upcoming+ECVAM+Validation+Study+on+In+Vitro+Skin+Irritation+Tests+&#8212;+An+Assessment+of+the+Performance+of+the+Optimised+Test.">The EpiDerm Test Protocol for the Upcoming ECVAM Validation Study on In Vitro Skin Irritation Tests &#8212; An Assessment of the Performance of the Optimised Test.</a> Altern Lab Anim. 33, 351-367 (2005).</li></ol>

Publication fees for this article were paid by MatTek Corporation. The authors are employees of MatTek Corporation.

We have presented the Eye Irritation Test (Figure 1) that was developed for the EpiOcular tissue model. The EIT is able to separate ocular irritants and corrosives (GHS Categories 1 and 2 combined) from materials that do not require labeling (GHS No Category) with high degree of sensitivity and specificity17. The EIT as presented herein does not discriminate between GHS Category 1 from Category 2 chemicals. The EIT was validated for classification and labeling of ocular irritation potential of a wide range of chemicals, including cosmetic and pharmaceutical ingredients. In conjunction with other in vitro tests, the EIT will serve as a replacement for the in vivo rabbit eye irritation test.
The EIT uses two similar but distinct protocols for liquid and solid materials, which vary in the length of exposure and post-exposure incubation periods (Figure 1). The endpoint used in the EIT is tissue viability, determined by the MTT assay, which has been previously used in validated human epithelial tissue models20,21. To perform this assay, no special equipment besides standard cell culture equipment is needed. Due to the high level of tissue-to-tissue reproducibility, n = 2 tissues instead of the usually recommended n = 3 are used. The ability to use n= 2 tissues is a critical aspect of the protocol, since it allows an experienced operator to process two tissues simultaneously, thereby minimizing the variability of the assay that can arise due to the different handling of individual tissues14. Also, by using n = 2 tissues per test article, the irritancy of 10 test substances of the same physical state (liquid or solid), along with the positive and negative controls, can be evaluated using one kit (24 tissues).
Other key points that ensure reliable classification of materials are specifications for the positive control substance (tissue viability &#8804;50.0%), reproducibility between duplicate tissues (difference &#60;20.0%), and negative control OD readings (&#62;0.8 and &#60;2.5).
When performing the EIT test, it is important to adhere to the validated protocol and to the suggested dosing and rinsing schedules (Tables 3 and 4), since deviation from the protocol or changes in the incubation periods may result in altered outcome. Likewise, deviations from the 3 hr time for MTT incubation will result in different MTT readings and may affect assay result.
Occasionally, a test chemical may have optical or other properties which may interfere with MTT tissue viability assay or cause reduction of MTT. For instance, a test chemical may directly reduce MTT into blue-purple reaction product, or may be a colored substance that absorbs light in the same range as MTT formazan (~570 nm). However, these test chemicals will present a problem only, if at the time of the MTT assay, a sufficient amount of the material is still present on (or absorbed by) the tissue. To avoid this interference, extensive rinsing procedures are incorporated into the EIT protocol. If rinsing does not remove the TA and the TA interferes with MTT reduction, additional controls must be used to detect and correct for it. Briefly, if direct MTT reduction of the test chemical is suspected, 50 &#181;l (or 50 mg for solids) of the chemical in question is incubated for 3 hr with working MTT solution at SCC (NC, 50 &#181;l of sterile deionized water, should be run concurrently). If the MTT solution turns blue-purple, the test article is presumed to have reduced the MTT. In this case a functional check using freeze-killed tissue controls should be performed to evaluate whether the test material is binding to the tissue and leading to a false MTT reduction signal. If there is appreciable MTT reduction in the TA-exposed, killed tissue control (relative to the amount in the untreated viable tissue), the mean tissue viability of the test article must be corrected by subtracting the mean viability of the killed control.
The EIT errs on the side of safety, as demonstrated by the low incidence of false negative classifications14,15,18. Importantly, none of the GHS Category 1 chemicals, which are corrosive to the eye and which represent the most serious ocular hazard, were classified as non-irritating in this assay14,15,18,19. Finally, one of the major advantages of the RhCE in vitro test method is the possibility of testing neat liquid and solid materials (which is not possible with two-dimensional, submerged cell cultures).
The EIT will &#160;contribute significantly in determining the ocular irritation potential of a wide range of materials according to the UN GHS classification and labeling system. The replacement of animals to determine ocular toxicity has been a goal of toxicological research for many years. The EIT test method has completed a formal validation study supported by EURL ECVAM in 2014 and the EpiOcular EIT was implemented into the OECD test Guidelines as OECD TG 492&#160;in 2015.

Consumer products such as cosmetics, detergents, and household cleaners include a variety of chemicals that may induce serious damage if they contact the eyes. Therefore, testing of these agents for eye irritation is required by the US and EU regulatory agencies to ensure consumer safety1. An assessment of the eye irritation potential of mixtures and formulations is also a requirement for complying with REACH (Registration, Evaluation, Authorization, and Restriction of Chemicals) legislation for the labeling of cosmetic ingredients under the EU Cosmetics Directive for transport of chemicals, and for the labeling of pesticides and household products2. Currently, regulatory agencies require ocular hazard assessment using the Globally Harmonized System of Classification and Labeling of Chemicals (GHS)3. GHS is mainly based on the Draize eye irritation test, the most widely used eye irritation assay in which foreign substances and mixtures are introduced directly into the conjunctival sac of the rabbit eye4. According to GHS classification, GHS Category 1 (ocular corrosives) refers to test chemicals that cause severe initial injury to the eye tissues or serious damage to the eye and vision which is not fully reversible within 21 days following exposure3,5. GHS Category 2 refers to test chemicals that produce significant changes in the eye that are fully reversible within 21 days of exposure. Test chemicals that are not corrosives or irritants are referred to as GHS No Category.
For more than 40 years, the Draize rabbit eye test has been criticized for its lack of reproducibility, overestimation of human responses, and the use of live animals5-8. These concerns have encouraged many proposals for refinement, reduction, and replacement of the in&#160;vivo&#160;test9. The need for validated non-animal alternatives was further strengthened by the adoption of the Seventh Amendment to the Cosmetics Directive, which banned the use of animals in the safety evaluation of cosmetic products (in 2005) and ingredients (in 2009)2.
Since 1996, the reconstructed cornea-like tissue model has been widely used by the cosmetic industry to evaluate the irritation potential of raw materials, surfactant-based formulations, and compounded mixtures that are designed for use in, or in the vicinity of, the eye10-13. Use of the RhCE tissue model allows direct topical application of the test material onto the tissue surface in its native, undiluted form. In this way, non-water soluble formulations can be tested without diluting them with solvents. In response to EURL ECVAM&#8217;s (European Union Reference Laboratory European Centre for the Validation of Alternative Methods) request for a widely applicable, straightforward, and economic method the Eye Irritation Test (EIT) which utilizes a single exposure time and is able to separate ocular irritants and corrosives from materials that do not require labeling was developed (Figure 1)14. Based on the results for 83 chemicals (44 liquids and 39 solids), the EIT achieved 95.5/68.2/ and 81.8% sensitivity/specificity and accuracy (SS&#38;A) for liquids, 100.0/68.4/ and 84.6% SS&#38;A for solids, and 97.6/68.3/ and 83.1% for overall SS&#38;A.
In 2007, a multi-laboratory pre-validation study sponsored by Cosmetics Europe (formerly Colipa) under the auspices of the EURL ECVAM assessed the relevance and reliability of the EIT with the goal of bringing it to formal validation15. In this study, 298 independent trials were performed in seven independent laboratories. Study results demonstrated 99.7% agreement in prediction with low coefficients of variation across all participating laboratories15. As a result, in 2010 the EIT protocol entered a formal EURL ECVAM validation program. The validation study utilized 104 coded test chemicals, including individual substances and chemical mixtures, for which in vivo reference data (Draize eye irritation data) were available. Based on the success of this work, an OECD draft test guideline was submitted in 2014. It is anticipated that the EIT will contribute significantly to classification of ocular irritation potential of a wide range of materials according to the UN GHS classification and labeling system.

eye irritation test (eit) for hazard identification of eye irritating chemicals using reconstructed human cornea-like epithelial (rhce) tissue model

To comply with the Seventh Amendment to the EU Cosmetics Directive and EU REACH legislation, validated non-animal alternative methods for reliable and accurate assessment of ocular toxicity in man are needed. To address this need, we have developed an eye irritation test (EIT) which utilizes a three dimensional reconstructed human cornea-like epithelial (RhCE) tissue model that is based on normal human cells. The EIT is able to separate ocular&#160;irritants and corrosives (GHS Categories 1 and 2 combined) and those that do not require labeling (GHS No Category). The test utilizes two separate protocols, one designed for liquid chemicals and a second, similar protocol for solid test articles. The EIT prediction model uses a single exposure period (30 min for liquids, 6 hr for solids) and a single tissue viability cut-off (60.0% as determined by the MTT assay). Based on the results for 83 chemicals (44 liquids and 39 solids) EIT achieved 95.5/68.2/ and 81.8% sensitivity/specificity and accuracy (SS&#38;A) for liquids, 100.0/68.4/ and 84.6% SS&#38;A for solids, and 97.6/68.3/ and 83.1% for overall SS&#38;A. The EIT will contribute significantly to classifying the ocular irritation potential of a wide range of liquid and solid chemicals without the use of animals to meet regulatory testing requirements. The EpiOcular EIT method was implemented in 2015 into the OECD Test Guidelines as TG 492.

Watch this Scientific Journal Video about Eye Irritation Test EIT for Hazard Identification of Eye Irritating Chemicals using Reconstructed Human Cornea-like Epithelial RhCE Tissue Model at JoVE.com

Eye Irritation Test EIT for Hazard Identification of Eye Irritating Chemicals using Reconstructed Human Cornea-like Epithelial RhCE Tissue Model

We have developed an eye irritation test which utilizes a three dimensional reconstructed human cornea-like epithelial (RhCE) tissue model. The test is able to discriminate between ocular irritant and corrosive materials (GHS Categories 1 and 2 combined) and those that do not require labeling (GHS No Category).

Eye Irritation Test (EIT) for Hazard Identification of Eye Irritating Chemicals using Reconstructed Human Cornea-like Epithelial (RhCE) Tissue Model

To comply with the Seventh Amendment to the EU Cosmetics Directive and EU REACH legislation, validated non-animal alternative methods for reliable and ...

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Bioengineering

36.9K Views.  MatTek Corporation. We have developed an eye irritation test which utilizes a three dimensional reconstructed human cornea-like epithelial (RhCE) tissue model. The test is able to discriminate between ocular irritant and corrosive materials (GHS Categories 1 and 2 combined) and those that do not require labeling (GHS No Category).

Video: Eye Irritation Test EIT for Hazard Identification of Eye Irritating Chemicals using Reconstructed Human Cornea-like Epithelial RhCE Tissue Model

Evaluation of Polymeric Gene Delivery Nanoparticles by Nanoparticle Tracking Analysis and High-throughput Flow Cytometry

Non-viral gene delivery using polymeric nanoparticles has emerged as an attractive approach for gene therapy to treat genetic diseases1 and as a technology for regenerative medicine2. Unlike viruses, which have significant safety issues, polymeric nanoparticles can be designed to be non-toxic, non-immunogenic, non-mutagenic, easier to synthesize, chemically versatile, capable of carrying larger nucleic acid cargo and biodegradable and/or environmentally responsive. Cationic polymers self-assemble with negatively charged DNA via electrostatic interaction to form complexes on the order of 100 nm that are commonly termed polymeric nanoparticles. Examples of biomaterials used to form nanoscale polycationic gene delivery nanoparticles include polylysine, polyphosphoesters, poly(amidoamines)s and polyethylenimine (PEI), which is a non-degradable off-the-shelf cationic polymer commonly used for nucleic acid delivery1,3 . Poly(beta-amino ester)s (PBAEs) are a newer class of cationic polymers4 that are hydrolytically degradable5,6 and have been shown to be effective at gene delivery to hard-to-transfect cell types such as human retinal endothelial cells (HRECs)7, mouse mammary epithelial cells8, human brain cancer cells9 and macrovascular (human umbilical vein, HUVECs) endothelial cells10.
A new protocol to characterize polymeric nanoparticles utilizing nanoparticle tracking analysis (NTA) is described. In this approach, both the particle size distribution and the distribution of the number of plasmids per particle are obtained11. In addition, a high-throughput 96-well plate transfection assay for rapid screening of the transfection efficacy of polymeric nanoparticles is presented. In this protocol, poly(beta-amino ester)s (PBAEs) are used as model polymers and human retinal endothelial cells (HRECs) are used as model human cells. This protocol can be easily adapted to evaluate any polymeric nanoparticle and any cell type of interest in a multi-well plate format.

A protocol for nanoparticle tracking analysis (NTA) and high-throughput flow cytometry to evaluate polymeric gene delivery nanoparticles is described. NTA is utilized to characterize the nanoparticle particle size distribution and the plasmid per particle distribution. High-throughput flow cytometry enables quantitative transfection efficacy evaluation for a library of gene delivery biomaterials.

Non-viral gene delivery using polymeric nanoparticles has emerged as an attractive approach for gene therapy to treat genetic diseases1 and as a ...

Tissue Engineering of a Human 3D in vitro Tumor Test System

Cancer is one of the leading causes of death worldwide. Current therapeutic strategies are predominantly developed in 2D culture systems, which inadequately reflect physiological conditions in vivo. Biological 3D matrices provide cells an environment in which cells can self-organize, allowing the study of tissue organization and cell differentiation. Such scaffolds can be seeded with a mixture of different cell types to study direct 3D cell-cell-interactions. To mimic the 3D complexity of cancer tumors, our group has developed a 3D in vitro tumor test system.	
	Our 3D tissue test system models the in vivo situation of malignant peripheral nerve sheath tumors (MPNSTs), which we established with our decellularized porcine jejunal segment derived biological vascularized scaffold (BioVaSc). In our model, we reseeded a modified BioVaSc matrix with primary fibroblasts, microvascular endothelial cells (mvECs) and the S462 tumor cell line. For static culture, the vascular structure of the BioVaSc is removed and the remaining scaffold is cut open on one side (Small Intestinal Submucosa SIS-Muc). The resulting matrix is then fixed between two metal rings (cell crowns).	
	Another option is to culture the cell-seeded SIS-Muc in a flow bioreactor system that exposes the cells to shear stress. Here, the bioreactor is connected to a peristaltic pump in a self-constructed incubator. A computer regulates the arterial oxygen and nutrient supply via parameters such as blood pressure, temperature, and flow rate. This setup allows for a dynamic culture with either pressure-regulated pulsatile or constant flow.	
	In this study, we could successfully establish both a static and dynamic 3D culture system for MPNSTs. The ability to model cancer tumors in a more natural 3D environment will enable the discovery, testing, and validation of future pharmaceuticals in a human-like model.

Tissue Engineering of a Human 3D in vitro Tumor Test System

Methods to create human 3D tumor tissues as test systems are described. These technologies are based on a decellularized Biological Vascularized Scaffold (BioVaSc), primary human cells and a tumor cell line, which can be cultured under static as well as under dynamic conditions in a flow bioreactor.

Cancer is one of the leading causes of death worldwide.  Current therapeutic strategies are predominantly developed in 2D culture  systems, which ...

Human Cartilage Tissue Fabrication Using Three-dimensional Inkjet Printing Technology

Bioprinting, which is based on thermal inkjet printing, is one of the most attractive enabling technologies in the field of tissue engineering and regenerative medicine. With digital control&#160;cells, scaffolds, and growth factors can be precisely deposited to the desired two-dimensional (2D) and three-dimensional (3D) locations rapidly. Therefore, this technology is an ideal approach to fabricate tissues mimicking their native anatomic structures. In order to engineer cartilage with native zonal organization, extracellular matrix composition (ECM), and mechanical properties, we developed a bioprinting platform using a commercial inkjet printer with simultaneous photopolymerization capable for 3D cartilage tissue engineering. Human chondrocytes suspended in poly(ethylene glycol) diacrylate (PEGDA) were printed for 3D neocartilage construction via layer-by-layer assembly. The printed cells were fixed at their original deposited positions, supported by the surrounding scaffold in simultaneous photopolymerization. The mechanical properties of the printed tissue were similar to the native cartilage. Compared to conventional tissue fabrication, which requires longer UV exposure, the viability of the printed cells with simultaneous photopolymerization was significantly higher. Printed neocartilage demonstrated excellent glycosaminoglycan (GAG) and collagen type II production, which was consistent with gene expression. Therefore, this platform is ideal for accurate cell distribution and arrangement for anatomic tissue engineering.

The methods described in this paper show how to convert a commercial inkjet printer into a bioprinter with simultaneous UV polymerization. The printer is capable of constructing 3D tissue structure with cells and biomaterials. The study demonstrated here constructed a 3D neocartilage.

Bioprinting, which is based on thermal inkjet printing, is one of the most attractive enabling technologies in the field of tissue engineering and ...

Assessing Leukocyte-endothelial Interactions Under Flow Conditions in an Ex Vivo Autoperfused Microflow Chamber Assay

Leukocyte-endothelial interactions are early and critical events in acute and chronic inflammation and can, when dysregulated, mediate tissue injury leading to permanent pathological damage. Existing conventional assays allow the analysis of leukocyte adhesion molecules only after the extraction of leukocytes from the blood. This requires the blood to undergo several steps before peripheral blood leukocytes (PBLs) can be ready for analysis, which in turn can stimulate PBLs influencing the research findings. The autoperfused micro flow chamber assay, however, allows scientists to study early leukocytes functional dysregulation using the systemic flow of a live mouse while having the freedom of manipulating a coated chamber. Through a disease model, the functional expression of leukocyte adhesion molecules can be assessed and quantified in a micro-glass chamber coated with immobilized endothelial adhesion molecules ex vivo. In this model, the blood flows between the right common carotid artery and left external jugular vein of a live mouse under anesthesia, allowing the interaction of native PBLs in the chamber. Real-time experimental analysis is achieved with the assistance of an intravital microscope as well as a Harvard Apparatus pressure device. The application of a flow regulator at the input point of the glass chamber allows comparable physiological flow conditions amongst the experiments. Leukocyte rolling velocity is the main outcome and is measured using the National Institutes of Health open-access software ImageJ. In summary, the autoperfused micro flow chamber assay provides an optimal physiological environment to study leukocytes endothelial interaction and allows researchers to draw accurate conclusions when studying inflammation.

Assessing Leukocyte-endothelial Interactions Under Flow Conditions in an Ex Vivo Autoperfused Microflow Chamber Assay

Here, we present a protocol that allows the investigator to assess leukocyte recruitment dynamics ex vivo by connecting a chamber coated with endothelial-derived adhesion molecules to the circulatory system of a mouse. This method offers significant advantages since it allows for leukocyte assessment under relative biological conditions.

Leukocyte-endothelial interactions are early and critical events in acute and chronic inflammation and can, when dysregulated, mediate tissue injury ...

Production, Characterization and Potential Uses of a 3D Tissue-engineered Human Esophageal Mucosal Model

The incidence of both esophageal adenocarcinoma and its precursor, Barrett&#8217;s Metaplasia, are rising rapidly in the western world. Furthermore esophageal adenocarcinoma generally has a poor prognosis, with little improvement in survival rates in recent years. These are difficult conditions to study and there has been a lack of suitable experimental platforms to investigate disorders of the esophageal mucosa.
A model of the human esophageal mucosa has been developed in the MacNeil laboratory which, unlike conventional 2D cell culture systems, recapitulates the cell-cell and cell-matrix interactions present in vivo and produces a mature, stratified epithelium similar to that of the normal human esophagus. Briefly, the model utilizes non-transformed normal primary human esophageal fibroblasts and epithelial cells grown within a porcine-derived acellular esophageal scaffold. Immunohistochemical characterization of this model by CK4, CK14, Ki67 and involucrin staining demonstrates appropriate recapitulation of the histology of the normal human esophageal mucosa.
This model provides a robust, biologically relevant experimental model of the human esophageal mucosa. It can easily be manipulated to investigate a number of research questions including the effectiveness of pharmacological agents and the impact of exposure to environmental factors such as alcohol, toxins, high temperature or gastro-esophageal refluxate components. The model also facilitates extended culture periods not achievable with conventional 2D cell culture, enabling, inter alia, the study of the impact of repeated exposure of a mature epithelium to the agent of interest for up to 20 days. Furthermore, a variety of cell lines, such as those derived from esophageal tumors or Barrett&#8217;s Metaplasia, can be incorporated into the model to investigate processes such as tumor invasion and drug responsiveness in a more biologically relevant environment.

This manuscript describes the production, characterization and potential uses of a tissue engineered 3D esophageal construct prepared from normal primary human esophageal fibroblast and squamous epithelial cells seeded within a de-cellularized porcine scaffold. The results demonstrate the formation of a mature stratified epithelium similar to the normal human esophagus.

The incidence of both esophageal adenocarcinoma and its precursor, Barrett&#8217;s Metaplasia, are rising rapidly in the western world. Furthermore ...

Encapsulated Cell Technology for the Delivery of Biologics to the Mouse Eye

Many current therapeutics under development for diseases of the posterior pole of the eye are biologics. These drugs need to be administered frequently, typically via intravitreal injections. Encapsulated cells expressing the biologic of choice are becoming a tool for local protein production and release (e.g., via long-term drug delivery). In addition, encapsulation systems utilize permeable materials that allow diffusion of nutrients, waste, and therapeutic factors into and out of cells. This occurs while masking the cells from the host immune response, avoiding the need for suppression of the host immune system. This protocol describes the use of alginate as a polymer in microencapsulation coupled with the electrospray method as a microencapsulation technique. ARPE-19 cells, a spontaneously arising human RPE cell line, has been used in long-term cell therapy experiments due to its lifetime functionality, and it is used here for encapsulation and delivery of the capsules to mouse eyes. The manuscript summarizes the steps for cell microencapsulation, quality control, and ocular delivery.

Presented here is a protocol for the use of alginate as a polymer in microencapsulation of immortalized cells for long-term delivery of biologics to rodent eyes.

Many current therapeutics under development for diseases of the posterior pole of the eye are biologics. These drugs need to be administered frequently, ...

Growth of Human and Sheep Corneal Endothelial Cell Layers on Biomaterial Membranes

Corneal endothelial cell cultures have a tendency to undergo epithelial-to-mesenchymal transition (EMT) after loss of cell-to-cell contact. EMT is deleterious for the cells as it reduces their ability to form a mature and functional layer. Here, we present a method for establishing and subculturing human and sheep corneal endothelial cell cultures that minimizes the loss of cell-to-cell contact. Explants of corneal endothelium/Descemet&#39;s membrane are taken from donor corneas and placed into tissue culture under conditions that allow the cells to collectively migrate onto the culture surface. Once a culture has been established, the explants are transferred to fresh plates to initiate new cultures. Dispase II is used to gently lift clumps of cells off tissue culture plates for subculturing. Corneal endothelial cell cultures that have been established using this protocol are suitable for transferring to biomaterial membranes to produce tissue-engineered cell layers for transplantation in animal trials. A custom-made device for supporting biomaterial membranes during tissue culture is described and an example of a tissue-engineered graft composed of a layer of corneal endothelial cells and a layer of corneal stromal cells on either side of a collagen type I membrane is presented.

This protocol describes the critical steps required to establish and grow corneal endothelial cell cultures from explants of human or sheep tissue. A method for subculturing corneal endothelial cells on membranous biomaterials is also presented.

Corneal endothelial cell cultures have a tendency to undergo epithelial-to-mesenchymal transition (EMT) after loss of cell-to-cell contact. EMT is ...

In Vitro Model of Human Cutaneous Hypertrophic Scarring using Macromolecular Crowding

It has been shown that in vivo tissues are highly crowded by proteins, nucleic acids, ribonucleoproteins, polysaccharides, etc. The following protocol applies a macromolecular crowding (MMC) technique to mimic this physiological crowding through the addition of neutral polymers (crowders) to cell cultures in vitro. Previous studies using Ficoll or dextran as crowders demonstrate that the expression of collagen I and fibronectin in WI38 and WS-1 cell lines are significantly enhanced using the MMC technique. However, this technique has not been validated in primary hypertrophic scar-derived human skin fibroblasts (hHSFs). As hypertrophic scarring arises from the excessive deposition of collagen, this protocol aims to construct a collagen-rich in vitro hypertrophic scar model by applying the MMC technique with hHSFs. This optimized MMC model has been shown to possess more similarities with in vivo scar tissue compared to traditional 2-dimensional (2-D) cell culture systems. In addition, it is cost-effective, time-efficient, and ethically desirable compared to animal models. Therefore, the optimized model reported here offers an advanced &#8220;in vivo-like&#8221; model for hypertrophic scar-related studies.

This protocol describes the use of macromolecular crowding to create an in vitro human hypertrophic scar tissue model that resembles in vivo conditions. When cultivated in a crowded macromolecular environment, human skin fibroblasts exhibit phenotypes, biochemistry, physiology, and functional characteristics resembling scar tissue.

It has been shown that in vivo tissues are highly crowded by proteins, nucleic acids, ribonucleoproteins, polysaccharides, etc. The following protocol ...

Cultivating a Three-dimensional Reconstructed Human Epidermis at a Large Scale

A three-dimensional human epidermis model reconstructed from neonatal primary keratinocytes is presented. Herein, a protocol for the cultivation process and the characterization of the model is described. Neonatal primary keratinocytes are grown submerged on permeable polycarbonate inserts and lifted to the air-liquid interface three days after seeding. After fourteen days of stimulation with defined growth factors and ascorbic acid in high calcium culture medium, the model is fully differentiated. Histological analysis revealed a completely stratified epidermis, mimicking the morphology of native human skin. To characterize the model and its barrier functions, protein levels and localization specific for early-stage keratinocyte differentiation (i.e., keratin 10), late-stage differentiation (i.e., involucrin, loricrin, and filaggrin) and tissue adhesion (i.e., desmoglein 1), were assessed by immunofluorescence. The tissue barrier integrity was further evaluated by measuring transepithelial electrical resistance. Reconstructed human epidermis was responsive to proinflammatory stimuli (i.e., lipopolysaccharide and tumor necrosis factor alpha), leading to increased cytokine release (i.e., interleukin 1 alpha and interleukin 8). This protocol represents a straightforward and reproducible in vitro method to cultivate reconstructed human epidermis as a tool to assess environmental effects and a broad range of skin-related studies.

This protocol describes a straightforward method to cultivate three-dimensional reconstituted human epidermis in a reproducible and robust manner. Additionally, it characterizes the structure-function relationship of the epidermal barrier model. The biological responses of the reconstituted human epidermis upon proinflammatory stimuli are also presented.

A three-dimensional human epidermis model reconstructed from neonatal primary keratinocytes is presented. Herein, a protocol for the cultivation process ...

Quantifying Fibrillar Collagen Organization with Curvelet Transform-Based Tools

Fibrillar collagens are prominent extracellular matrix (ECM) components, and their topology changes have been shown to be associated with the progression of a wide range of diseases including breast, ovarian, kidney, and pancreatic cancers. Freely available fiber quantification software tools are mainly focused on the calculation of fiber alignment or orientation, and they are subject to limitations such as the requirement of manual steps, inaccuracy in detection of the fiber edge in noisy background, or lack of localized feature characterization. The collagen fiber quantitation tool described in this protocol is characterized by using an optimal multiscale image representation enabled by curvelet transform (CT). This algorithmic approach allows for the removal of noise from fibrillar collagen images and the enhancement of fiber edges to provide location and orientation information directly from a fiber, rather than using the indirect pixel-wise or window-wise information obtained from other tools. This CT-based framework contains two separate, but linked, packages named &#8220;CT-FIRE&#8221; and &#8220;CurveAlign&#8221; that can quantify fiber organization on a global, region of interest (ROI), or individual fiber basis. This quantification framework has been developed for more than ten years and has now evolved into a comprehensive and user-driven collagen quantification platform. Using this platform, one can measure up to about thirty fiber features including individual fiber properties such as length, angle, width, and straightness, as well as bulk measurements such as density and alignment. Additionally, the user can measure fiber angle relative to manually or automatically segmented boundaries. This platform also provides several additional modules including ones for ROI analysis, automatic boundary creation, and post-processing. Using this platform does not require prior experience of programming or image processing, and it can handle large datasets including hundreds or thousands of images, enabling efficient quantification of collagen fiber organization for biological or biomedical applications.

Here, we present a protocol to use a curvelet transform-based, open-source MATLAB software tool for quantifying fibrillar collagen organization in the extracellular matrix of both normal and diseased tissues. This tool can be applied to images with collagen fibers or other types of line-like structures.

Fibrillar collagens are prominent extracellular matrix (ECM) components, and their topology changes have been shown to be associated with the progression ...