The authors wish to acknowledge funding from the National Institutes of Health (R01AI155922). Microscopy was performed at the Chapel Hill Analytical and Nanofabrication Laboratory (CHANL), a member of the North Carolina Research Triangle Nanotechnology Network, RTNN, which is supported by the National Science Foundation, Grant ECCS-1542015, as part of the National Nanotechnology Coordinated Infrastructure, NNCI.

All animal experiments were conducted in accordance with the Animal Welfare Act and the Public Health Service Policy on Humane Care and Use of Laboratory Animals. The study protocol was approved by the Institutional Animal Care and Use Committee of the University of Tennessee Health Science Center. Healthy female BALB/c mice, ~6-8 weeks old, were administered the dry powder content of one dosator by intrapulmonary aerosol delivery for a pharmacokinetic study using spectinamide 1599 dry powders9. The animals were obtained from a commercial source (see Table of Materials).
1. Preparation of the dosator and the filling components
<ol>
	<li>Trim the plastic luer portion of a 2.54 cm (1 inch) blunt stainless-steel needle (21-25 G) using either a precision sectioning saw (see Table of Materials), or a belt sander until 2-3 mm of the plastic luer remains (Figure 1A and Figure 2A). 
	NOTE: If a belt sander is used, the stainless-steel needle may need to be cleaned using a smaller needle or wire to remove the possible obstructions created.</li>
	<li>Cut off the tip (1-1.5 cm) of a 0.6 mL conical centrifuge tube. Fill the tip of the tube with 30-35 mg of powder. 
	&#8203;NOTE: See Representative Results for the details of the example powders used for the present study. The powder aerosol performance should be evaluated prior to use in this application following standard methodology as described in USP General Chapter &#60;601&#62; (see Table of Materials).</li>
	<li>If storing and/or transporting the powder, use the tube cap (cut off) to close the vial. Seal with paraffin film to minimize powder exposure to ambient moisture if storing and/or transporting.</li>
</ol>
2. Loading and assembling dosators
<ol>
	<li>Tamp the trimmed stainless-steel needle into the powder bed in the 0.6 mL conical centrifuge tube tip as many times as needed to achieve the desired dose (Figure 2B). Gently wipe the sides of the stainless-steel needle with a low-lint wiper to remove any excess powder (Figure 3).</li>
	<li>Gently insert the loaded stainless-steel needle into a 3.81 cm (1.5 inch) polypropylene or 5.08 cm (2 inch) polytetrafluoroethylene (PTFE) needle (16-20 G) (see Table of Materials) to avoid dislodging any powder (Figure 1B,C and Figure 2C).</li>
</ol>
3. Actuating dosators
<ol>
	<li>Draw back a disposable syringe to the desired volume, which may vary based on application. 
	NOTE: For intrapulmonary administration in mice, 0.15-0.6 mL is typically appropriate8,9.</li>
	<li>Attach the syringe to the luer lock on the polypropylene or PTFE needle (Figure 2D).</li>
	<li>Insert the needle end of the dosator into the desired target. For analyzing powder content and reproducibility, insert the needle through a perforated rubber septum or paraffin film into a vial containing a small amount (e.g., 1-5 mL) of water and/or organic solvent (e.g., ethanol), with solvent identity and volume dependent on active pharmaceutical ingredient (API) physical characteristics and the quantification method.
	<ol>
		<li>For delivery to mice, insert the needle up to the first bronchial bifurcation of the trachea of anesthetized mice following established protocols9,15.</li>
	</ol>
	</li>
	<li>Depress the syringe forcefully, expelling the powder out of the device into the collection vial (Figure 2E). 
	NOTE: The same technique must be followed for delivering the powder to the murine lungs.</li>
	<li>For analyzing content and reproducibility from the collection vial, utilize an appropriate analytical method for the specific API, such as UV-Visible (UV-Vis) spectrophotometry or high-performance liquid chromatography (HPLC).</li>
</ol>

Customizable Disposable Dosators to Deliver Dry Powder Aerosol Drugs to Mice

<ol>
	<li>Wu, X., Li, X., Mansour, H. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Surface+analytical+techniques+in+solid-state+particle+characterization+for+predicting+performance+in+dry+powder+inhalers.">Surface analytical techniques in solid-state particle characterization for predicting performance in dry powder inhalers.</a> KONA Powder and Particle Journal. 28, 3-18 (2010).</li><li>Maloney, S. E., Mecham, J. B., Hickey, A. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Performance+testing+for+dry+powder+inhaler+products:+towards+clinical+relevance.">Performance testing for dry powder inhaler products: towards clinical relevance.</a> KONA Powder and Particle Journal. 40, 172-185 (2023).</li><li>Maloney, S. E., 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=Spray+dried+tigecycline+dry+powder+aerosols+for+the+treatment+of+nontuberculous+mycobacterial+pulmonary+infections.">Spray dried tigecycline dry powder aerosols for the treatment of nontuberculous mycobacterial pulmonary infections.</a> Tuberculosis. 139, 102306 (2023).</li><li>Kaur, J., 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=A+hand-held+apparatus+for+&amp;#34;nose-only&amp;#34;+exposure+of+mice+to+inhalable+microparticles+as+a+dry+powder+inhalation+targeting+lung+and+airway+macrophages.">A hand-held apparatus for &amp;#34;nose-only&amp;#34; exposure of mice to inhalable microparticles as a dry powder inhalation targeting lung and airway macrophages.</a> European Journal of Pharmaceutical Sciences. 34 (1), 56-65 (2008).</li><li>Yi, J., 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=Whole-body+nanoparticle+aerosol+inhalation+exposures.">Whole-body nanoparticle aerosol inhalation exposures.</a> Journal of Visualized Experiments. (75), e50263 (2013).</li><li>Chung, Y. H., Han, J. H., Lee, Y. -. 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+study+on+subchronic+inhalation+toxicology+of+1-chloropropane.">A study on subchronic inhalation toxicology of 1-chloropropane.</a> Toxicological Research. 31 (4), 393-402 (2015).</li><li>Kuehl, P. J., 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=Regional+particle+size+dependent+deposition+of+inhaled+aerosols+in+rats+and+mice.">Regional particle size dependent deposition of inhaled aerosols in rats and mice.</a> Inhalation Toxicology. 24 (1), 27-35 (2012).</li><li>Manser, 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=Design+considerations+for+intratracheal+delivery+devices+to+achieve+proof-of-concept+dry+powder+biopharmaceutical+delivery+in+mice.">Design considerations for intratracheal delivery devices to achieve proof-of-concept dry powder biopharmaceutical delivery in mice.</a> Pharmaceutical Research. 40, 1165-1176 (2023).</li><li>Stewart, I. E., 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=Development+and+characterization+of+a+dry+powder+formulation+for+anti-tuberculosis+drug+spectinamide+1599.">Development and characterization of a dry powder formulation for anti-tuberculosis drug spectinamide 1599.</a> Pharmaceutical Research. 36 (9), 136 (2019).</li><li>Durham, P. G., 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=Disposable+dosators+for+pulmonary+insufflation+of+therapeutic+agents+to+small+animals.">Disposable dosators for pulmonary insufflation of therapeutic agents to small animals.</a> Journal of Visualized Experiments. (121), e55356 (2017).</li><li>Miwata, K., 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=Intratracheal+administration+of+siRNA+dry+powder+targeting+vascular+endothelial+growth+factor+inhibits+lung+tumor+growth+in+mice.">Intratracheal administration of siRNA dry powder targeting vascular endothelial growth factor inhibits lung tumor growth in mice.</a> Molecular Therapy: Nucleic Acids. 12, 698-706 (2018).</li><li>Duret, 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=Pharmacokinetic+evaulation+in+mice+of+amorphous+itraconazole-based+dry+powder+formulations+for+inhalation+with+high+bioavailability+and+extended+lung+retention.">Pharmacokinetic evaulation in mice of amorphous itraconazole-based dry powder formulations for inhalation with high bioavailability and extended lung retention.</a> European Journal of Pharmaceutics and Biopharmaceutics. 86 (1), 46-54 (2014).</li><li>Maloney, S. E., 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+strategies+of+the+anti-mycobacterial+drug+bedaquiline+for+intrapulmonary+routes+of+administration.">Preparation strategies of the anti-mycobacterial drug bedaquiline for intrapulmonary routes of administration.</a> Pharmaceuticals. 16 (5), 729 (2023).</li><li>Price, D. N., Kunda, N. K., Muttil, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Challenges+associated+with+the+pulmonary+delivery+of+therapeutic+dry+powders+for+preclinical+testing.">Challenges associated with the pulmonary delivery of therapeutic dry powders for preclinical testing.</a> KONA Powder and Particle Journal. 36, 129-144 (2019).</li><li>Qiu, Y., Liao, Q., Chow, M. Y. T., Lam, J. K. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Intratracheal+administration+of+dry+powder+formulation+in+mice.">Intratracheal administration of dry powder formulation in mice.</a> Journal of Visualized Experiments. (161), e61469 (2020).</li><li>Fiegel, J., 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+and+in+vivo+evaluation+of+a+dry+powder+for+inhalation+of+capreomycin.">Preparation and in vivo evaluation of a dry powder for inhalation of capreomycin.</a> Pharmaceutical Research. 25 (4), 805-811 (2008).</li></ol>

The authors declare that they have no conflict of interest.

As mice are obligate nose breathers, delivery via passive inhalation for initial proof-of-concept studies makes efficiency and dose estimation challenging as the powder must pass the nose and throat in a manner dependent on particle properties and powder dispersion efficiency7,8,14. The use of the dosators developed herein bypasses the nose and throat, with the dosator inserted to the first bronchial bifurcation<sup cla...

The use of dry powder inhalers (DPIs) for pulmonary drug delivery has garnered significant interest over the past three decades due to the global phase-out of chlorofluorocarbon propellants1,2. DPIs offer numerous benefits over other pulmonary delivery systems, such as metered dose inhalers and nebulizers, including formulation stability, portability, ease of use, and propellant-free dispersal mechanisms2. However, before moving DPI products toward clinical translation, several preclinical studies must be conducted, many of which are initially completed using a murine model. Nevertheless, technologies available to deliver dry powders accurately and reproducibly to small animals are limited.
Common methods to deliver dry powders to small animals, such as mice, include passive inhalation3,4,5,6,7 and direct administration8,9,10,11,12,13. Passive inhalation typically requires a custom chamber that utilizes large doses of spray-dried powder to prepare a sufficient aerosol cloud. As mice are obligate nose breathers14, delivery by passive inhalation requires the powder to travel through the nose and throat to reach the lungs, necessitating the maintenance of an aerosol cloud with sufficient particle aerodynamic properties7,8. While a useful technique that is more physiologically relevant than direct delivery due to inhalation as a result of normal breathing14, it may not be suitable for initial studies where powder mass is limited.
Alternatively, a number of intratracheal delivery devices for direct dry powder delivery have been reported8,9,10,11,12,13. Intratracheal devices bypass the nose and throat, delivering the powder directly to the lungs and allowing for finer control over the delivered dose14. Additionally, some devices, especially those prepared using a tamping loading procedure9, can be prepared with smaller quantities, which is an important consideration for initial proof-of-concept studies. The lack of universally available intratracheal delivery devices has hindered their potential for use, limiting availability and leading to interlaboratory differences14. In this study, we propose a simple, inexpensive, disposable dosator for intratracheal delivery that can be utilized for proof-of-concept murine studies in the development of dry powder aerosols.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>0.6 mL microcentrifuge tubes</td>
			<td>Fisher Scientific</td>
			<td>05-408-120</td>
			<td></td>
		</tr>
		<tr>
			<td>Analytical balance</td>
			<td>Mettler Toledo</td>
			<td>AR1140</td>
			<td>Any analytical balance with sufficient range can be used</td>
		</tr>
		<tr>
			<td>Blunt stainless-steel needle, 1 inch, 21 G</td>
			<td>McMaster-Carr</td>
			<td>75165A681</td>
			<td></td>
		</tr>
		<tr>
			<td>Blunt stainless-steel needle, 1 inch, 22 G</td>
			<td>McMaster-Carr</td>
			<td>75165A683</td>
			<td></td>
		</tr>
		<tr>
			<td>Blunt stainless-steel needle, 1 inch, 25 G</td>
			<td>McMaster-Carr</td>
			<td>75165A687</td>
			<td></td>
		</tr>
		<tr>
			<td>Disposable syringe with luer lock (1 mL)</td>
			<td>Fisher Scientific</td>
			<td>14-823-30</td>
			<td>3-mL syringes can also be used</td>
		</tr>
		<tr>
			<td>Female BALB/c mice&#160;</td>
			<td>Charles River, Wilmington, MA, USA</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>High-performance cascade impactor&#160;</td>
			<td>Next Generation Impactor</td>
			<td>Apparatus 5</td>
			<td></td>
		</tr>
		<tr>
			<td>Lab film (e.g., Parafilm)</td>
			<td>Fisher Scientific</td>
			<td>S37440</td>
			<td></td>
		</tr>
		<tr>
			<td>Low-lint wiper (e.g., Kimwipes)</td>
			<td>Kimberly-Clark Professional</td>
			<td>34133</td>
			<td></td>
		</tr>
		<tr>
			<td>Low-resistance dry powder inhaler&#160;</td>
			<td>RS01 mod 7</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Polypropylene needle, 1.5 inch, 16 G</td>
			<td>McMaster-Carr</td>
			<td>6934A111</td>
			<td></td>
		</tr>
		<tr>
			<td>Polypropylene needle, 1.5 inch, 18 G</td>
			<td>McMaster-Carr</td>
			<td>6934A53</td>
			<td></td>
		</tr>
		<tr>
			<td>Polypropylene needle, 1.5 inch, 20 G</td>
			<td>McMaster-Carr</td>
			<td>6934A55</td>
			<td></td>
		</tr>
		<tr>
			<td>Precision sectioning saw</td>
			<td>TedPella</td>
			<td>812-300</td>
			<td>Belt sander can be used as an alternative</td>
		</tr>
		<tr>
			<td>PTFE needle, 2 inch, 20 G</td>
			<td>McMaster-Carr</td>
			<td>75175A694</td>
			<td></td>
		</tr>
		<tr>
			<td>USP General Chapter &#60;601&#62;&#160;</td>
			<td></td>
			<td></td>
			<td>http://www.uspbpep.com/usp31/v31261/usp31nf26s1_c601.asp</td>
		</tr>
	</tbody>
</table>

disposable dosators intended for dry powder delivery to mice

Dry powder inhalers offer numerous advantages for delivering drugs to the lungs, including stable solid-state drug formulations, device portability, bolus metering and dosing, and a propellant-free dispersal mechanism. To develop pharmaceutical dry powder aerosol products, robust in vivo testing is essential. Typically, initial studies involve using a murine model for preliminary evaluation before conducting formal studies in larger animal species. However, a significant limitation in this approach is the lack of suitable device technology to accurately and reproducibly deliver dry powders to small animals, hindering such models&#39; utility. To address these challenges, disposable syringe dosators were developed specifically for intrapulmonary delivery of dry powders in doses appropriate for mice. These dosators load and deliver a predetermined amount of powder obtained from a uniform bulk density powder bed. This discrete control is achieved by inserting a blunt needle to a fixed depth (tamping) into the powder bed, removing a fixed quantity each time. Notably, this dosing pattern has proven effective for a range of spray-dried powders. In experiments involving four different model spray-dried powders, the dosators demonstrated the ability to achieve doses within the range of 30 to 1100 &#181;g. The achieved dose was influenced by factors such as the number of tamps, the size of the dosator needle, and the specific formulation used. One of the key benefits of these dosators is their ease of manufacturing, making them accessible and cost-effective for delivering dry powders to mice during initial proof-of-concept studies. The disposable nature of the dosators facilitates use in animal procedure rooms, where cleaning and refilling reusable systems and weighing materials is inconvenient. Thus, developing disposable syringe dosators has addressed a significant hurdle in murine dry powder delivery for proof-of-concept studies, enabling researchers to conduct more accurate and reproducible preliminary studies in small animal models for pulmonary drug delivery.

Author Spotlight: Developing a Disposable Dosator for Preclinical Testing of Dry Powder Inhalers in Small Animal Models 

Disposable Dosators Intended for Dry Powder Delivery to Mice

The aerosol performance&#160;of various spray-dried powders was established prior to use in this study. The aerodynamic particle size distribution (APSD) was described by the mass median aerodynamic diameter (MMAD), representing the size that divides the distribution in two at the 50th percentile (d50), and the geometric standard deviation (GSD), reflecting the breadth of the distribution. The GSD is defined by the square root of the aerodynamic diameter at the 80th percentile divided by ...

Watch this Scientific Journal Video about Developing a Disposable Dosator for Preclinical Testing of Dry Powder Inhalers in Small Animal Models at JoVE.com

Pharmaceutical dry powder development necessitates reliable in vivo testing, often using a murine model. Device technology for accurately and reproducibly delivering dry powder aerosols to mice is restricted. This study presents disposable dosators for pulmonary drug delivery at mouse-relevant doses, aiding initial proof-of-concept research.

Dry powder inhalers offer numerous advantages for delivering drugs to the lungs, including stable solid-state drug formulations, device portability, bolus ...

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648 Views.  RTI International. Pharmaceutical dry powder development necessitates reliable in vivo testing, often using a murine model. Device technology for accurately and reproducibly delivering dry powder aerosols to mice is restricted. This study presents disposable dosators for pulmonary drug delivery at mouse-relevant doses, aiding initial proof-of-concept research.

Video: Author Spotlight: Developing a Disposable Dosator for Preclinical Testing of Dry Powder Inhalers in Small Animal Models 

Assembling and Actuating a Disposable Dosator for Dry Powder Drug Delivery

To prepare the disposable dosator and its filling components, take a 2.5 centimeter or 1 inch blunt stainless steel needle of 21 to 25 gauge. Utilizing a precision sectioning saw or a belt sander, trim the plastic lure part of the needle, leaving about 2 to 3 millimeters of the plastic lure attached to the needle. Next, cut off approximately 1 to 1.5 centimeters from the tip of a 0.6 milliliter conical centrifuge tube.After that, fill this cut tip with 30 to 35 milligrams of the powder of interest. For storing or transporting the powder, place the cutoff tube cap onto the cut tip containing the powder. Use paraffin film to wrap the cover, minimizing the powder's exposure to ambient moisture.To load the dosator, tamp the trimmed stainless steel needle into the powder bed in the cut tip as many times as required to achieve the desired dose. Using a low lint wiper, gently wipe the sides of the needle to remove any excess powder. Then take a 3.81 centimeter or 1.5 inch polypropylene needle of 16 to 20 gauge and cautiously insert the loaded stainless steel needle into it, making sure not to dislodge any powder.Alternatively, use a 5.08 centimeter or 2 inch PTFE needle for the same. To actuate the dosator, first draw back a disposable syringe to the desired volume based on the application. Then attach the syringe to the lure lock on the polypropylene or PTFE needle before inserting the needle end of the dosator into the desired target.To analyze powder content and reproducibility, insert the dosator needle through a perforated rubber septum or paraffin film into a vial with a small quantity of liquid. Forcefully depress the syringe plunger, expelling the powder from the device into the collection vial. Finally, analyze the powder solution in the vial using UV's visible spectra photometry to monitor the dose of the powder released from the dosator.Four different spray dried powders visualized using scanning electron microscopy were considered for delivery using the demonstrated dosator. The delivered dose as a function of the number of Tamps in the powder bed, was obtained from UV visible spectra photometry of the powder solutions. Notably, all spray dried powders demonstrated a linear dose response from 1 to 4 Tamps.The first Tamp always incurred a larger dose of powder than subsequent Tamps. When compared to the demonstrated 21 gauge stainless steel with a 16 gauge polypropylene dosator, a slight increase in achievable dose was observed using a 21 gauge stainless steel with a 20 gauge PTFE dosator for powder SD 1. As expected, the achievable dose of SD 1 decreased for a 22 gauge stainless steel with an 18 gauge polypropylene dosator, having a smaller inner needle diameter.A 25 gauge stainless steel with a 20 gauge polypropylene dosator further decreased the initial and subsequent Tamp doses. This is a comparison of the four dosator systems that were evaluated, highlighting that the dosators can be customized to meet different dosage needs.