Name: Dissolving Microneedle Array Patches Manufactured By Solvent Casting Technique and Essential Characterization of Microneedle-Based Biomedical Devices (Video) | JoVE Journal
Uploaded: 2026-01-30T14:40:00.000+00:00
Duration: 8 min 26 s
Description: Learn to fabricate dissolving microneedle array patches using solvent casting for transdermal drug delivery. This protocol covers preparation, characterization, and ex vivo testing methods for biomedical applications.

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5 minutes

This publication is part of the grant PID2020-114530GA-I00 funded by MCIN/AEI/10.13039/501100011033. Illustration in Figure 1 was created using Biorender.com under an active license.

The reagents and equipment used in this study are listed in the Table of Materials.
1. Manufacture of Dissolving Microneedle Arrays by centrifugation
<ol>
	<li>Prepare the aqueous colloidal dispersion of the constituent materials of DMAPs by dissolving them in the appropriate amount of water and stirring vigorously. Depending on the selected polymers and concentration, the dispersion time might vary. If needed, warm up the water moderately (40-45 °C) to facilitate the dispersion of the polymer. 
	NOTE: The most common polymers used to prepare DMAPs are poly(vinyl pyrrolidone) (PVP), karaya gum, hyaluronic acid (HA), poly(methyl vinyl ether alt-maleic acid) (PMVE-MA), poly(vinyl alcohol) (PVA), carboxymethyl cellulose (CMC), chitosan, etc., however, any other water-soluble material with optimal properties can be used. For most formulations, the typical working concentration ranges from 5% to 30% w/w. Lower concentrations generally produce fast-dissolving DMAPs, while higher concentrations yield slow-dissolving devices. However, the optimal concentration must be determined empirically by preparing different DMAP prototypes, as it depends on the polymer's molecular weight, viscosity, and the desired mechanical properties of the microneedles.</li>
	<li>Allow the polymers to stir minimally overnight to achieve complete dispersion, while allowing air bubbles to be removed.</li>
	<li>Centrifuge the polymeric dispersion if air bubbles persist (1000 x g; 5 min; 25 °C).</li>
	<li>Add the cargo (drug or nanosized particle) at the desired concentration and stir moderately until it is homogeneous without incorporating new air bubbles.</li>
	<li>Dispose of PDMS molds into 12-well plates. For that, accommodate the molds into the wells with modeling clay, dental cement, or any similar material.</li>
	<li>Cast 50 µL of the drug-loaded polymeric blend onto the PDMS molds and centrifuge (3000 x g; 5 min; 25 °C). Afterwards, turn the plates 180°, and repeat the centrifugation process to ensure the filling of all needle-like cavities.</li>
	<li>Carefully remove the excess of drug-loaded polymeric dispersion. Use a pipette to transfer the polymeric dispersion if it is liquid; use a spatula if it is highly viscous.</li>
	<li>Repeat the double centrifugation process (step 1.6) to put back into the mold any drug-loaded polymeric dispersion that might have overflowed during the previous step.</li>
	<li>Dry the drug-loaded polymeric dispersion in the molds under vacuum (600 mBar; 30 min; 25 °C).</li>
	<li>Repeat the protocol at least twice from step 1.6-1.9 to ensure the correct filling of the master molds with the drug-loaded polymeric dispersion. 
	NOTE: The centrifugal force can be progressively reduced by means of 500 x g (25 °C) in each repetition.</li>
	<li>Prepare a highly concentrated polymeric dispersion free of drug to make the baseplate of the DMAPs device. It will ensure that the drug present in the dispersion filled in the mold cavities does not flow back to the baseplate.</li>
	<li>Cast 50 µL of the free-drug polymeric dispersion onto the PDMS molds and spread by centrifuging twice, including midpoint plates, at a turn of 180° (500 x g; 5 min; 25 °C; 2x). After centrifugation, add 100 µL of the dispersion to each mold, followed by the addition of an additional 50 µL to the baseplate after 12 h.</li>
	<li>Leave the DMAPs in the PDMS molds to dry for 3-5 days at room temperature in a dry-seal desiccator.</li>
	<li>Demold the DMAPs from PDMS carefully with forceps or peel them off using scotch cellulose tape (Figure 1).</li>
	<li>Characterize the manufactured DMAPs (see step 3).</li>
</ol>
2. Manufacture of Dissolving Microneedle Arrays by applying positive pressure
<ol>
	<li>Proceed similarly as described in the previous section until step 1.5.</li>
	<li>Cast 150 µL of the drug-loaded polymeric blend onto the PDMS molds and place them into a pressure tank.</li>
	<li>Fill the pressure tank with air until it reaches a pressure of 3-4 bar for at least 15 min.</li>
	<li>Carefully remove the excess of drug-loaded polymeric dispersion. For that, if the polymeric dispersion is liquid, use a pipette, whereas if it is considerably viscous, remove it with a spatula.</li>
	<li>Repeat pressure application (steps 2.2-2.3) to put back into the mold any drug-loaded polymeric dispersion that might have overflowed during the previous step.</li>
	<li>Dry the drug-loaded polymeric dispersion in the molds under vacuum (600 mbar; 30 min; 25 °C).</li>
	<li>Prepare a highly concentrated polymeric dispersion free of drug to make the baseplate of the DMAPs device. It will ensure that the drug present in the dispersion filled in the mold cavities does not flow back to the baseplate.</li>
	<li>Cast 0.2 g of the free-drug polymeric dispersion onto the PDMS molds and apply a positive pressure, as described in step 2.3.</li>
	<li>Proceed similarly as described in the previous section from step 1.13.</li>
</ol>
3. Characterization of DMAPs
NOTE: In this step, methods involving the use of human and/or animal skin tissues were performed in accordance with institutional guidelines. Additionally, the methods involving the use of animal skin samples were carried out in accordance with the 3Rs principle for animal experimentation.
<ol>
	<li>Visualize the DMAPs using a micro-camera with the appropriate magnification to distinguish the needle-like projections7. 
	NOTE: If they have been loaded with a colored drug or dye, a different color must be observed between the tips and the baseplate.</li>
	<li>Attach the DMAPs to a support device and visualize the morphology and length of microneedle-like projections by optical microscopy. A sharp tip structure must be observed. Record the length of microneedle-like projections with the appropriate software for your optical microscope. 
	NOTE: To measure the microneedle length by optical microscopy, MAPs must be displayed perpendicular to the objectives. Length measurements and the shape of microneedle-like projections must be confirmed by Scanning Electron Microscopy.</li>
	<li>Evaluate the mechanical properties of DMAPs towards the microneedles' deformation after compression to a solid surface. For that, place the DMAPs device into a commercially available DMAPs applicator and compress it against a stainless-steel flat surface for 30 s. After compressing, record the microneedle-like projections' length and calculate the deformation percentage by comparing it with the initial length according to the following equation7: 
	<img alt="Compression percentage formula, \( \text{Compression (\%)} = \frac{h_o - h_f}{h_o} \times 100 \), equation." src="/files/ftp_upload/69923/69923eq1.jpg" style="margin: auto;" data-altupdatedat="1778558422000" data-alt="Equation 1"> 
	Where, ho and hf stand for microneedles' length before and after the compression, respectively. 
	​NOTE: If available, the use of a texture analyzer standardizes the compression force. In that case, a force of 32 N/array mimics the average thumb force that patients apply when self-administering DMAPs devices.</li>
	<li>Determine the preliminary insertion capacity of DMAPs by a surrogate artificial skin method based on thermoplastic sheets made of olefin-type material8. For that, compress the DMAPs device against eight bound sheets following the conditions described in step 3.4. The number of holes created in each layer is observed by optical microscopy or using a microscope camera, and the percentage of penetration at different depths is calculated. 
	NOTE: Commercially available thermoplastic sheets usually present a thickness of 127 µm.</li>
	<li>Determine the ex vivo insertion capacity of DMAPs using human, porcine, or rodent skin explants previously excised and carefully trimmed. Clean the skin explant with abundant water by soaking for 1-2 min in water and then place it onto an aluminum foil-wrapped foam material with the stratum corneum side facing upwards.
	<ol>
		<li>Proceed with the insertion under the conditions described in step 3.4. Leave the DMAPs inserted into the skin until the dissolution of the microneedle tips. If DMAPs are loaded with a dye or colored drug, the coloring of the internal and external sides of the skin reveals a successful DMAPs insertion9. Besides, microchannels can be observed by histological analysis of skin sections7. 
		NOTE: This step, involving ex vivo human or animal skin, was conducted in accordance with the guidelines and approval of the University of Valencia Human and Animal Research Ethics Committee. Informed consent was obtained where applicable, and all experiments adhered to institutional and European ethical standards for the use of human and animal tissues in biomedical research.</li>
	</ol>
	</li>
	<li>Determine the residual water content by Thermogravimetric analysis. Weight loss observed until 100-110 °C is attributed to the residual water10. 
	NOTE: Depending on the literature source, the maximum residual water content allowed is 5%-10% of the total weight to ensure optimal drying of DMAPs.</li>
	<li>Quantify the cargo loading by immersing the DMAPs in 5-10 mL of water (or alternatively, an appropriate aqueous release medium for the analyzed drug) at 32-37 °C and quantifying the cargo amount using an optimal analytical method. 
	NOTE: UV-Vis spectrophotometry is commonly used for the analysis of small molecules. For compounds with low detection and quantification limits, high-performance liquid chromatography (HPLC) coupled with UV-Vis, fluorescence, or electrochemical detection is highly recommended. HPLC coupled with mass spectrometry can be employed when exceptional sensitivity and specificity are required. The analytical determination of protein and antibody cargos is typically performed using bicinchoninic acid (BCA) assays and immunoassays, such as enzyme-linked immunosorbent assay (ELISA) or Western blotting, respectively. Drug release profiles are obtained by sampling (0.2-1 mL) at predetermined time points from the release aqueous media11. After every sampling point, the subtracted volume is replaced with the same volume of tempered release media in order to avoid errors related to auto-concentration of samples.</li>
	<li>Assess the stability of DMAPs by repeating the above-mentioned characterization assays to ensure that DMAPs' features remain constant during the storage period under the designed storage conditions. 
	NOTE: If the cargo is thermostable, DMAPs are typically stored at room temperature (25 °C). For thermosensitive active ingredients, DMAPs are stored at 4 °C. The relative humidity should be maintained below 30%. The stability of DMAPs is routinely monitored over a six-month period.</li>
	<li>Determine the ex vivo drug skin deposition and absorption through the skin using a Franz-diffusion cell (FDC) setup. For this, prepare the skin as described and insert the DMAPs into the skin structure for 30 s, as described in step 3.6.
	<ol>
		<li>Afterwards, glue the donor chamber of FDC to the skin with an appropriate amount of cyanoacrylate. When dried, attach the skin-donor chamber complex to the receptor chamber using appropriate clamps12. Finally, proceed with the sampling protocol as described in subsection 3.5. 
		NOTE: This step involving ex vivo human or animal skin was conducted in accordance with the guidelines and approval of the University of Valencia Human and Animal Research Ethics Committee. Informed consent was obtained where applicable, and all experiments adhered to institutional and European ethical standards for the use of human and animal tissues in biomedical research. If DMAPs dissolve slowly, secure them to the skin using surgical adhesive bands to prevent auto-expulsion from the skin structure.</li>
	</ol>
	</li>
	<li>Assess in vitro biocompatibility using metabolic activity assays, such as Tetrazolium-based and Resazurin-based assays, or proliferation tests, including 5-Bromo-2'-deoxyuridine bromodeoxyuridine (BrdU) assays, according to the manufacturer's instructions. 
	NOTE: Preferred cell lines are keratinocytes, fibroblasts, or melanocytes. Cells unexposed to DMAPs are typically used as negative controls, whereas cells treated with 1% sodium dodecyl sulfate (SDS) serve as positive controls. Biocompatibility assessment depends on the dissolution profile of the DMAPs. For fast-dissolving DMAPs (dissolving within 24 h), the extract-based method is used, where the device is dissolved prior to cell exposure. For slow-dissolving DMAPs, the direct contact method is applied, with the device added directly to the seeded wells. According to the international standards ISO 10993 regulation, cell viability results &gt;70% are considered non-toxic.</li>
</ol>

<ol><li>Bos, J. D., Meinardi, M. M. H. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((The+500+Dalton+rule+for+the+skin+penetration+of+chemical+compounds+and+drugs%5BTitle%5D)+AND+%22Exp+Dermatol%22%5BJournal%5D)">The 500 Dalton rule for the skin penetration of chemical compounds and drugs.</a> Exp Dermatol. 9 (3), 165-169 (2000).</li>
<li>Guillot, A. J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Microneedle-based+delivery%3A+An+overview+of+current+applications+and+trends%5BTitle%5D)+AND+%22Pharmaceutics%22%5BJournal%5D)">Microneedle-based delivery: An overview of current applications and trends.</a> Pharmaceutics. 12 (6), 569(2020).</li>
<li>Guillot, A. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Exploration+of+microneedle-assisted+skin+delivery+of+cyanocobalamin+formulated+in+ultraflexible+lipid+vesicles%5BTitle%5D)+AND+%22Eur+J+Pharm+Biopharm%22%5BJournal%5D)">Exploration of microneedle-assisted skin delivery of cyanocobalamin formulated in ultraflexible lipid vesicles.</a> Eur J Pharm Biopharm. S0939-6411 (22), 00138-00142 (2022).</li>
<li>Kalluri, H., Banga, A. K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Formation+and+closure+of+microchannels+in+skin+following+microporation%5BTitle%5D)+AND+%22Pharm+Res%22%5BJournal%5D)">Formation and closure of microchannels in skin following microporation.</a> Pharm Res. 28 (1), 82-94 (2011).</li>
<li>Guillot, A. J., Melero, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((%28Re%29evolution+in+nanoparticles-loaded+microneedle+delivery+systems%3A+are+we+getting+closer+to+a+clinical+translation%5BTitle%5D)+AND+%22Nanomedicine%22%5BJournal%5D)">(Re)evolution in nanoparticles-loaded microneedle delivery systems: are we getting closer to a clinical translation.</a> Nanomedicine. 20 (10), 1195-1207 (2025).</li>
<li>Guillot, A. J., Martínez-Navarrete, M., Bernabeu-Martínez, J. A., Cordeiro, A. S., Melero, A. <a target="_blank" href="http://scholar.google.com/scholar?hl=en&safe=off&q=author%3aGuillot%2C+AJ+%22Microneedles%3A+Fabrication%2C+characterization+and+translational+potential%22">Microneedles: Fabrication, characterization and translational potential</a>. , Springer. Singapore. doi: 10.1007/978-981-96-3916-8_1 (2025).</li>
<li>Guillot, A. J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Cyanocobalamin-loaded+dissolving+microneedles+diminish+skin+inflammation+in+vivo%5BTitle%5D)+AND+%22J+Control+Release%22%5BJournal%5D)">Cyanocobalamin-loaded dissolving microneedles diminish skin inflammation in vivo.</a> J Control Release. 375, 537-551 (2024).</li>
<li>Larrañeta, E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((A+proposed+model+membrane+and+test+method+for+microneedle+insertion+studies%5BTitle%5D)+AND+%22Int+J+Pharm%22%5BJournal%5D)">A proposed model membrane and test method for microneedle insertion studies.</a> Int J Pharm. 472 (1), 65-73 (2014).</li>
<li>Martínez-Navarrete, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Cyclosporin+A-loaded+dissolving+microneedles+for+dermatitis+therapy%3A+Development%2C+characterisation+and+efficacy+in+a+delayed-type+hypersensitivity+in+vivo+model%5BTitle%5D)+AND+%22Drug+Deliv+Transl+Res%22%5BJournal%5D)">Cyclosporin A-loaded dissolving microneedles for dermatitis therapy: Development, characterisation and efficacy in a delayed-type hypersensitivity in vivo model.</a> Drug Deliv Transl Res. 14 (12), 3404-3421 (2024).</li>
<li>Kolluru, C., Gomaa, Y., Prausnitz, M. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Development+of+a+thermostable+microneedle+patch+for+polio+vaccination%5BTitle%5D)+AND+%22Drug+Deliv+Transl+Res%22%5BJournal%5D)">Development of a thermostable microneedle patch for polio vaccination.</a> Drug Deliv Transl Res. 9 (1), 192-203 (2019).</li>
<li>Larrañeta, E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((A+facile+system+to+evaluate+in+vitro+drug+release+from+dissolving+microneedle+arrays%5BTitle%5D)+AND+%22Int+J+Pharm%22%5BJournal%5D)">A facile system to evaluate in vitro drug release from dissolving microneedle arrays.</a> Int J Pharm. 497 (1-2), 62-69 (2016).</li>
<li>Martínez-Navarrete, M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Enhanced+ex+vivo+skin+retention+of+bicalutamide+using+a+nano-in-micro+composite%3A+drug-loaded+lipid+vesicles+in+a+dissolving+microarray+patch%5BTitle%5D)+AND+%22Eur+J+Pharm+Biopharm%22%5BJournal%5D)">Enhanced ex vivo skin retention of bicalutamide using a nano-in-micro composite: drug-loaded lipid vesicles in a dissolving microarray patch.</a> Eur J Pharm Biopharm. 212, 114728(2025).</li>
<li>Mansoor, I., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Microneedle-based+vaccine+delivery%3A+Review+of+an+emerging+technology%5BTitle%5D)+AND+%22AAPS+PharmSciTech%22%5BJournal%5D)">Microneedle-based vaccine delivery: Review of an emerging technology.</a> AAPS PharmSciTech. 23 (4), 1-12 (2022).</li>
<li>Guillot, A. J., Martínez-Navarrete, M., Zinchuk-Mironova, V., Melero, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Microneedle-assisted+transdermal+delivery+of+nanoparticles%3A+Recent+insights+and+prospects%5BTitle%5D)+AND+%22Wiley+Interdiscip+Rev+Nanomed+Nanobiotechnol%22%5BJournal%5D)">Microneedle-assisted transdermal delivery of nanoparticles: Recent insights and prospects.</a> Wiley Interdiscip Rev Nanomed Nanobiotechnol. 15 (4), e1884(2023).</li>
<li>ISO 10993-1:2018. Biological evaluation of medical devices - Part 1: Evaluation and testing within a risk management process. , ISO. 
 <a target="_blank" href="https://www.iso.org/standard/68936.html">https://www.iso.org/standard/68936.html</a> (2025).</li>
<li>ISO/TS 10993-19:2020. Biological evaluation of medical devices - Part 19: Physico-chemical, morphological and topographical characterization of materials. , ISO. 
 <a target="_blank" href="https://www.iso.org/standard/75138.html">https://www.iso.org/standard/75138.html</a> (2025).</li>
</ol>

The authors declare no conflicts of interest or relevant financial interests.

The protocol described here allows the preparation of DMAPs. However, the versatility and the wide range of polymeric materials that can be used for manufacturing DMAPs allow the production of dissolving devices with different features. The results presented correspond to fast-dissolving DMAPs, as they were produced with PVP, a highly water-dispersible polymer at a low concentration. The dissolution time of DMAPs can be easily tuned by simply substituting the constituent polymer or changing its concentration. Therefore, ...

Although topical and transdermal administration of pharmacologically active substances through and into the skin is considered a promising alternative to oral drug administration, it presents significant challenges due to the natural skin barrier function exerted by the stratum corneum layer. This limitation especially affects large molecules, particularly those with a molecular weight &#62;500 Da1. Additionally, passive diffusion through the skin of other molecules with specific physicochemical properties, such as notable hydrophilicity or lipophilicity, is also restricted. Different technological strategies have been proposed to overcome this barrier, including iontophoresis, sonophoresis, electroporation, the use of chemical enhancers, thermal methods, and nanosized systems. Nonetheless, Microneedle Array Patches (MAPs) stand out among them due to several advantages: extreme efficiency in nullifying the stratum corneum function, cost-effectiveness, a painless experience for patients, and the possibility of self-administration without the need for medical personnel2.
MAPs are devices that contain micro-sized needle-like projections that pierce the stratum corneum layer and bypass the epidermal barrier. Several MAPs types are described in the literature, namely: solid, coated, dissolving, swelling, and hollow MAPs. Dissolving MAPs (DMAPs) are composed of water-soluble polymeric materials and employ a &#34;poke and release&#34; strategy, which accounts for their extra interesting features. Particularly, they dissolve upon insertion into the skin structure when in contact with interstitial fluids, releasing their content. In comparison with the &#34;poke and patch&#34; strategy performed by solid MAPs, where they are used to create microchannels within the skin structure that allow the passage of a subsequently topically applied formulation3,4, the &#34;poke and release&#34; approach is not subjected to the time that microchannels remain open. The &#34;poke and flow&#34; strategy requires the preparation of hollow MAPs, whose architecture is considerably more complex and difficult to manufacture. An additional advantage of DMAPs is that they do not generate sharp&#160;waste after application, thereby reducing the risk of needle-stick injuries and biological contamination. Moreover, their simple and minimally invasive application enables potential self-administration by patients, supporting their use in resource-limited or geographically remote settings where access to trained healthcare personnel, medical infrastructure, and safe sharps disposal systems is limited2. The scientific community focused on dermal and transdermal drug delivery has increasingly turned to MAPs technology, particularly DMAPs, to overcome the limitations of the aforementioned strategies. Although the first publication on MAPs dates back to the 1980s, the technology experienced a major surge in the early 2000s. Since then, the number of publications has grown exponentially, reaching approximately 500 articles per year nowadays5.
DMAPs are commonly manufactured by the solvent-casting method or micromolding6. This manufacturing technique is based on the use of negative master molds of the desired MAPs shape and length. After casting polymeric dispersions loaded with drugs or even nanosized systems, an external force is applied to fill the microneedle-shaped cavities of the master mold. Once dried, DMAPs can be carefully demolded by peeling them off or dissolving the master mold with a chemical agent. These master molds are made of different materials, with polydimethylsiloxane (PDMS) being the most common, thanks to its flexibility and low adhesivity, which facilitates the demolding of DMAPs. The preparation of master molds is typically carried out using lithographic methods; however, commercial PDMS molds of various shapes, lengths, and densities of microneedles are now available.
Here, a guideline for the preparation of DMAPs using the solvent casting technique is provided. In this case, the process is performed using centrifugal force or the application of a positive pressure. This allows an efficient-cost protocol alternative to high-cost manufacturing methods of MAPs-based biomedical devices, enabling a broader group of researchers to incorporate MAPs in their skin-related research work. Additionally, the essential characterization for academic and basic research purposes that precedes in vivo testing includes needle length and geometry, mechanical resistance to compression, ex vivo insertion performance, drug loading and drug release, residual water content, stability, ex vivo drug absorption, and in vitro safety profile.

<table><tbody><tr><td>Cell culture 12-well plate</td><td>N/A</td><td>N/A</td><td>No specifications. Any commercial cell culture 12-well plate is suitable</td></tr><tr><td>Centrifuge</td><td>Eppendorf</td><td>Centrifuge 5810 G</td><td>Replaceable by any other centrifuge adaptable to cell culture plates</td></tr><tr><td>Methylene blue</td><td>Sigma Aldrich</td><td>66720</td><td>CAS 122965-43-9. Replaceable by any other dye or brand</td></tr><tr><td>Modelling clay</td><td>N/A</td><td>N/A</td><td>No specifications. Any commercial modelling clay is suitable</td></tr><tr><td>Olefin-type thermoplastic sheets</td><td>Amcor</td><td>PM996</td><td>Parafilm M</td></tr><tr><td>Poly(vinyl alcohol) (PVA) MW: 9-10 kDa</td><td>Sigma Aldrich</td><td>363146</td><td>CAS 9002-89-5. Replaceable by any other brand</td></tr><tr><td>Poly(vinyl pyrrolidone) (PVP) MW: 40 kDa</td><td>Sigma Aldrich</td><td>PVP40</td><td>CAS 9003-39-8. Replaceable by any other brand</td></tr><tr><td>Polydimethylsiloxane (PDMS) molds</td><td>Micropoint Technologies</td><td>ST-06</td><td>Array needle distribution 15 x 15; Height 600 &amp;micro;m; Base 200 &amp;micro;m; Needle Pitch 500 &amp;micro;m. Replaceable by any other PDMS mold with other cavity shape and length</td></tr><tr><td>Pressure Tank</td><td>Protrima</td><td>AT-10HT</td><td>Replaceable by any other pressure tank supporting 4 bar pressure</td></tr></tbody></table>

dissolving microneedle array patches manufactured by solvent casting technique and essential characterization of microneedle-based biomedical devices

Dissolving Microneedle Array Patches Manufactured By Solvent Casting Technique and Essential Characterization of Microneedle-Based Biomedical Devices

Microneedle-based technology has revolutionized the field of skin and transdermal delivery research and is considered nowadays as the most straightforward approach to administering drugs through the skin. Microneedle Array Patches (MAPs) success is mainly due to their ability to nullify the skin barrier function that opposes the entrance of topically applied drugs by painless piercing the stratum corneum layer. Dissolving MAPs (DMAPs) stand out among other MAPs-based device types due to the biocompatibility of their constituent materials, the possibility of self-administration by patients, and the absence of sharp waste generated after use. DMAPs are usually made of&#160;polymeric materials that redisperse upon insertion into the skin when in touch with interstitial fluids, releasing their cargo. At the bench level, DMAPs are commonly manufactured using the solvent casting method, which involves the use of negative master molds of the desired MAPs shape and length, onto which drug-loaded polymeric dispersions are cast. They are subsequently forced to fill the mold&#39;s cavities by the application of a centrifugal force or positive pressure. After drying, DMAPs become solid and are peeled off from the master molds, and they routinely undergo various characterization studies before use. These assays typically comprise the study of the mechanical properties of DMAPs, determination of residual water content, ex vivo capacity to penetrate the skin structure, drug release performance, and in vitro assessment of biocompatibility.

Manufactured DMAPs must denote a homogeneous appearance with a successful formation of microneedle-like projections, as shown in Figure 2A. When a colored cargo is loaded only into the microneedle structure, a small amount of drug can contaminate the baseplate of DMAPs due to drug overflow from the tips or incomplete cleaning before casting the free-drug polymeric dispersion. However, a clear difference is observed between the two structures. When visualized by optical microscopy, microneedl...

The present work aims to serve as a practical guide enabling researchers to prepare their own DMAP devices using the solvent-casting method, also known as micromolding, and to perform basic characterization.

Microneedle-based technology has revolutionized the field of skin and transdermal delivery research and is considered nowadays as the most straightforward ...

Our research mainly focuses on the optimization of a skin drug delivery using nano and microsystems, such as microneedle based devices. This study offers a feasible and reproducible method for preparing dissolving microneedles. To begin, prepare the aqueous colloidal dispersion of the constituent materials of DMAPs, by dissolving them in the appropriate amount of water.Stir the mixture vigorously to obtain a uniform dispersion. Allow the polymers to stir minimally overnight to achieve complete dispersion, and let the air bubbles disperse during this prolonged stirring period. If air bubbles persist, centrifuge the polymeric dispersion at 1000 G for five minutes at 25 degrees Celsius.Add the cargo at the desired concentration into the polymeric dispersion, and stir the mixture moderately until it becomes homogeneous without incorporating new air bubbles. Now, to accommodate the molds into the wells, use modeling clay or dental cement, and dispose the PDMS molds into the 12 well plate. Next, cast 20 microliters of the drug loaded polymeric blend onto the PDMS molds.Place the plate in the centrifuge, and spin at 3000 G for five minutes at 25 degrees Celsius. Now, turn the plate 180 degrees, and repeat the centrifugation to ensure filling of all needle-like cavities. Then, using a pipette, carefully remove the excess drug loaded polymeric dispersion from the molds.Dry the drug loaded polymeric dispersion in the molds by placing them under vacuum at 600 millibars for 30 minutes at 25 degrees Celsius. Prepare a highly concentrated polymeric dispersion free of drugs to form the base plate of the DMAP's device. Ensure the dispersion is homogeneous before use.Next, cast 50 microliters of the drug free polymeric dispersion onto the PDMS molds. Place the plate in the centrifuge and spin twice, including a midpoint plate rotation of 180 degrees. After centrifugation, add 100 microliters of dispersion to each mold, followed by an additional 50 microliters to the base plate after 12 hours.Leave the DMAPs in the PDMS molds to dry for three to five days at room temperature in a dry seal desiccater. Demold the DMAPs carefully from the PDMS molds using forceps. Alternatively, peel the DMAPs off the molds using scotch cellulose tape.For the positive pressure method, cast 150 microliters of the drug loaded polymeric blend onto the PDMS molds, and place them in a pressure tank. Fill the pressure tank with air until it reaches a pressure between three and four bar. Maintain this pressure for at least 15 minutes.Visualize the DMAPs using a micro camera with appropriate magnification to distinguish the needle-like projections. Adjust the focus to clearly resolve individual microneedles. Next, attach the DMAPs to a support device to visualize the morphology, and length of the microneedle-like projections by optical microscopy.Evaluate the mechanical properties of the DMAPs by placing the device into a commercially available DMAPs applicator. Compress the applicator against a stainless steel flat surface for 30 seconds. After compression, record the length of the microneedle-like projections and calculate the deformation percentage by comparing the length before and after compression.Then, determine the preliminary insertion capacity of the DMAPs using a surrogate artificial skin method based on thermoplastic sheets made of olefin type material. Compress the DMAPs device against eight bound sheets using the same compression conditions applied to the stainless steel surface. Now, determine the ex vivo insertion capacity of the DMAPs using human, porcine, or rodent skin explants that have been previously excised and carefully trimmed.Clean the skin explant by soaking it in abundant water for one to two minutes. Place the clean skin explant onto an aluminum foil wrapped foam material with the stratum corneum side facing upwards. Proceed with insertion using the same compression conditions previously described.Leave the DMAPs inserted into the skin until dissolution of the microneedle tips occurs, and observe the device remaining in contact with the skin during dissolution. Determine the ex vivo drug skin deposition and absorption using a Franz-Diffusion cell setup. Prepare the skin explant using the previously described trimming and cleaning procedure, and insert the DMAPs into the skin structure for 30 seconds.Glue the donor chamber of the Franz-Diffusion cell to the skin using an appropriate amount of cyanoacrylate. Allow the adhesive to dry completely, then attach the skin donor chamber complex to the receptor chamber using a appropriate clamps. Finally, proceed with sampling according to the standard diffusion cell protocol.Manufactured DMAPs displayed a homogeneous appearance with successful formation of microneedle-like projections, and the color dye was localized within the projections, with the base plate remaining free of drugs. Optical microscopy revealed that microneedle-like projections had sharp tip ends and no deformation before compression. After compression, microneedle-like projections showed visible deformation of structure.In an artificial skin model, DMAPs successfully penetrated the thermoplastic sheet, creating visible holes. The number of holes created in different layers of the thermoplastic model correlated with microneedle insertion depth. Ex-vivo murine skin explants showed progressive dying of the inner skin layers after insertion, consistent with DMAP dissolution over time.Histological examination with Eosin hematoxylin staining, confirmed insertion of microneedle-like projections into skin sections. A Franz-Diffusion cell setup was used to evaluate the diffusion of drugs through skin explants, with clear visualization of the donor chamber, skin, and receptor chamber. This protocol provides a foundational guideline for fabricating dissolving microneedle devices, enabling researchers to explore their design, performance and biomedical application potential.A key challenge is ensuring cargo compatibility with the polymer matrix. Certain cargoes may interfere with the material properties or compromise microneedle performance. Future studies can adapt this protocol to specific drugs and polymers, optimizing microneedles preparation, and expanding applications across therapeutic and biomedical uses.

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Research

JoVE Journal

Bioengineering

This article details the construction of a multiplexed microneedle-based sensor. The device is being developed for in situ sampling and electrochemical analysis of multiple analytes in a rapid and selective manner. We envision clinical medicine and biomedical research uses for these microneedle-based sensors.

Hollow Microneedle-based Sensor for Multiplexed Transdermal Electrochemical Sensing

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Polymeric Microneedle Array Fabrication by Photolithography

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Fabrication of a Master Mold for Microneedles with a Micron-sized Air-vent Hole

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Fabrication of Dissolvable Microneedle Patches Loaded with &#945;-Lactalbumin Nanomicelles for Transdermal Capsaicin Delivery and Adipose Tissue Reduction

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Graphene Coatings for Biomedical Implants

A novel vocal fold bioreactor capable of delivering physiologically relevant, vibratory stimulation to cultured cells is constructed and characterized. This dynamic culture device, when combined with a fibrous poly(ε-caprolactone) scaffold, creates a vocal fold-mimetic environment that modulates the behaviors of mesenchymal stem cells.

Construction and Characterization of a Novel Vocal Fold Bioreactor

This protocol details a method to isolate extracellular vesicles (EVs), small membranous particles released from cells, from as little as 10 μl serum samples. This approach circumvents the need for ultracentrifugation, requires only a few minutes of assay time, and enables the isolation of EVs from samples of limited volumes.

Paper-based Devices for Isolation and Characterization of Extracellular Vesicles

We present an experimental protocol to form a supported lipid bilayer on solid substrates without using lipid vesicles. We demonstrate a one-step method to form a lipid bilayer on silicon dioxide and gold as well as supported membranes with cholesterol-enriched domain for various biological applications.

Biomembrane Fabrication by the Solvent-assisted Lipid Bilayer (SALB) Method

Bioactive and mechanically reliable metal scaffolds have been fabricated through a method which consists of two processes, dynamic freeze casting for the fabrication of porous Ti, and coating and densification of the Ti scaffolds. The densification process is simple, effective and applicable to the fabrication of functionally graded scaffolds.

Fabrication of Mechanically Tunable and Bioactive Metal Scaffolds for Biomedical Applications

Learn to fabricate dissolving microneedle array patches using solvent casting for transdermal drug delivery. This protocol covers preparation, characterization, and ex vivo testing methods for biomedical applications.

Dissolving Microneedle Array Patches Manufactured By Solvent Casting Technique and Essential Characterization of Microneedle-Based Biomedical Devices (Video) | JoVE Journal

Dissolving Microneedle Array Patches Manufactured By Solvent Casting Technique and Essential Characterization of Microneedle-Based Biomedical Devices

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