Table 2.
Examples of different 3D printing methods used in the production of MN arrays for TDD systems.
| 3D Printing Method | Type of Microneedle Produced | Drug Model/Medical Agent | Material Used for Fabrication | Main Observations | References |
|---|---|---|---|---|---|
| Inkjet printing | Coated metal MNs | Insulin | Gelatin, polyvinyl caprolactame-polyvinyl acetate-polyethylene glycol, poly(2-ethyl-2-oxazoline), and trehalose | Rapid release rates for insulin were observed within the first 20 min; poly(2-ethyl-2-oxazoline) and gelatin were rapidly released from Franz diffusion cells from MNs implanted into porcine skin | [247] |
| Coated Gantrez 169 BF MNs | Amphotericin B | ------- | In a radial diffusion assay, controlled release of amphotericin-B was found to be effective against Candida parapsilosis | [248] | |
| Coated biodegradable polyglycolic acid MNs | Voriconazole | Polyglycolic acid MNs | MNs modified with voriconazole exhibited antifungal activity against Candida albicans, but not against Escherichia coli, Pseudomonas aeruginosa, or Staphylococcus aureus | [249] | |
| Coated metal MNs | 5-Fluororacil, curcumin, and cisplatin |
Hydrophilic graft copolymer Soluplus® | A fast release rate ranging from 3 h for 5-fluororacil to 1 h for curcumin and cisplatin throughout the highly precise coatings at different drug–polymer ratios in the produced MNs | [250] | |
| DLP | Dissolving MNs | Gold/silver nanoclusters | Polyvinyl alcohol/sucrose MNs | Gelatin with gold/silver nanocluster labels functioned as a fluorescent probe; DLP was used to develop an effective polyvinyl-alcohol-based MN patch; the skin patch could be easily removed to allow for additional nanocluster release | [251] |
| SLA | Biodegradable MNs | Dacarbazine (anticancer drug) | Dacarbazine-loaded poly(propylene fumarate) MN arrays | The controlled release rate for the drug extended to 5 weeks | [189] |
| FDM | Biodegradable MNs | Fluorescein | Polylactic acid | Fast printing of polymeric MN via customized needles; this polylactic acid was used to load small-molecule medications | [80] |
| Two-photon polymerization (2PP) 3D printing | Hollow MNs | ------- | Silicone | MNs with sufficient stability within skin tissue | [252] |
| Magnetic-field-assisted 3D printing | Biodegradable MNs | Fluorescein | Iron oxide nanoparticles encapsulated by photocurable E-glass resin | Fluorescein was reported to be released continuously from nanocomposite MNs, which could be inserted into the skin painlessly | [253] |
| Continuous liquid interface production (CLIP) | Biodegradable MNs | Fluorescent | Trimethylolpropane triacrylate, polyacrylic acid, and photopolymerizable derivatives of polyethylene glycol and polycaprolactone | The development of square pyramidal MNs made of different kinds of polymers; the MN patch was able to release the fluorescent drug surrogate and successfully penetrate murine skin | [254] |
| PolyJet 3D printer | Biodegradable MNs | Ovalbumin (model antigen) | Corn protein and zein | Zein MNs with a cast cone shape were successfully created; when compared to the application of a hypodermic syringe, considerably lower bacterial penetration through the skin was seen | [232] |
| Magnetorheological drawing lithography | Dissolving MNs | Rhodamine B | Polyvinyl alcohol and sucrose | MN arrays in the shape of cones were developed effectively on a flexible PET substrate; the patch demonstrated good strength, along with excellent and easy skin penetration; due to the MN patch’s creation of microchannels, drugs may be dispersed through the skin | [255] |