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In this focused progress review, the most widely accepted methods of transdermal drug delivery are hypodermic needles, transdermal patches and topical creams. However, microneedles (MNs) (or microneedle arrays) are low-invasive 3D biomedical constructs that bypass the skin barrier and produce systemic and localized pharmacological effects. In the past, biomaterials such as carbohydrates, due to their physicochemical properties, have been extensively used to manufacture microneedles (MNs). Due to their wide range of functional groups, carbohydrates enable the design and development of tunable properties and functionalities. In recent years, numerous microneedle products have emerged on the market, although much research needs to be undertaken to overcome the various challenges before the successful introduction of microneedles into the market. As a result, carbohydrate-based microarrays have a high potential to achieve a future step in sensing, drug delivery, and biologics restitution. In this review, a comprehensive overview of carbohydrates such as hyaluronic acid, chitin, chitosan, chondroitin sulfate, cellulose and starch is discussed systematically. It also discusses the various drug delivery strategies and mechanical properties of biomaterial-based MNs, the progress made so far in the clinical translation of carbohydrate-based MNs, and the promotional opportunities for their commercialization. In conclusion, the article summarizes the future perspectives of carbohydrate-based MNs, which are considered as the new class of topical drug delivery systems.

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Emtricitabine (ECB) is an anti-retroviral drug that inhibits HIV reverse transcriptase and prevents transcription of RNA to DNA. ECB exhibits high solubility and low permeability (log P < 0). To modify the diffusion behavior of ECB, a high throughput cocrystal screening has been carried out with coformers that contain carboxylic acid/amide functionalities via solvent assisted grinding. The screening study resulted in the formation of cocrystals with benzoic acid (BA), caprolactam (CPR), and salts with 2,6-dihydroxybenzoic acid (DHBA), malonic acid (MLN), maleic acid (MLE), and saccharin (SAC), which were confirmed with single crystal X-ray diffraction. In addition, 15N solid state NMR spectroscopy was exploited to define the ionization state of the multicomponent systems. The 2-aminopyrimidine homodimer of the cytosine analogue in the ECB is replaced by aminopyrimidine···carboxylic acid/amide in the cocrystals and aminopyrimidinium···carboxylate/saccharinate heterosynthons in the salts. The terminal hydroxyl group of the ECB forms a hydrogen bond with its carbonyl group, which is consistent in the ECB–BA cocrystal, ECB–DHBA and ECB–MLN salts. In addition, the hydroxyl group of ECB is hydrogen bonded with the relatively stronger acceptors like the carbonyl/sulfonyl group of caprolactam, maleate, and saccharinate in their corresponding multicomponent crystals. The diffusion studies of ECB multicomponent crystals using a Franz diffusion cell suggest that the ECB–BA cocrystal exhibited an enhanced diffusion and flux compared to that of native drug and other multicomponent crystals. An inverse correlation was observed partially between the flux values with crystal densities and binding energies of the ECB multicomponent systems.