Experimental and theoretical studies of drug-polymer interactions to control the drug distributions in dissolving microneedles

Advancing liposome technology for innovative strategies against malaria

This review discusses the potential of liposomes as drug delivery systems for antimalarial therapies. Malaria continues to be a significant cause of mortality and morbidity, particularly among children and pregnant women. Drug resistance due to patient non-compliance and troublesome side effects remains a significant challenge in antimalarial treatment. Liposomes, as targeted and efficient drug carriers, have garnered attention owing to their ability to address these issues. Liposomes encapsulate hydrophilic and/or hydrophobic drugs, thus providing comprehensive and suitable therapeutic drug delivery. Moreover, the potential of passive and active drug delivery enables drug concentration in specific target tissues while reducing adverse effects. However, successful liposome formulation is influenced by various factors, including drug physicochemical characteristics and physiological barriers encountered during drug delivery. To overcome these challenges, researchers have explored modifications in liposome nanocarriers to achieve efficient drug loading, controlled release, and system stability. Computational approaches have also been adopted to predict liposome system stability, membrane integrity, and drug-liposome interactions, improving formulation development efficiency. By leveraging computational methods, optimizing liposomal drug delivery systems holds promise for enhancing treatment efficacy and minimizing side effects in malaria therapy. This review consolidates the current understanding and highlights the potential of liposome strategies against malaria.

The most promising microneedle device: present and future of hyaluronic acid microneedle patch

Microneedle patch (MNP) is an alternative to the oral route and subcutaneous injection with unique advantages such as painless administration, good compliance, and fewer side effects. Herein, we report MNP as a prominent strategy for drug delivery to treat local or systemic disease. Hyaluronic acid (HA) has advantageous properties, such as human autologous source, strong water absorption, biocompatibility, and viscoelasticity. Therefore, the Hyaluronic acid microneedle patch (HA MNP) occupies a large part of the MNP market. HA MNP is beneficial for wound healing, targeted therapy of certain specific diseases, extraction of interstitial skin fluid (ISF), and preservation of drugs. In this review, we summarize the benefits of HA and cross-linked HA (x-HA) as an MNP matrix. Then, we introduce the types of HA MNP, delivered substances, and drug distribution. Finally, we focus on the biomedical application of HA MNP as an excellent drug carrier in some specific diseases and the extraction and analysis of biomarkers. We also discuss the future development prospect of HA MNP in transdermal drug delivery systems (TDDS).

Two-Layer Sustained-Release Microneedles Encapsulating Exenatide for Type 2 Diabetes Treatment

Daily administration of multiple injections can cause inconvenience and reduce compliance in diabetic patients; thus, microneedle (MN) administration is favored due to its various advantages. Accordingly, the two-layer sustained-release MNs (TS-MNs) were fabricated by encapsulating exenatide (EXT) in calcium alginate (CA) gel in this work. The TS-MNs were composed of a sodium alginate (SA) tip and a water-soluble matrix-containing calcium chloride (CaCl₂). Subsequently, the calcium ion (Ca²⁺) contained in the matrix layer penetrated the tip layer for cross-linking, leaving the drug in the cross-linked network. The patches have adequate mechanical strength to pierce the skin; then, the matrix layer is dissolved, leaving the tip layer to achieve sustained release. Additionally, the TS-MNs encapsulating EXT retained high activity during long-term storage at room temperature. The pharmacokinetic results indicated that the plasma concentrations of EXT were sustained for 48 h in the EXT MN group, which agreed with the in vitro release test. Furthermore, they had high relative bioavailability (83.04%). Moreover, the hypoglycemic effect was observed to last for approximately 24 h after a single administration and remained effective after multiple administrations without drug resistance. These results suggest that the TS-MNs are a promising depot for the sustained delivery of encapsulated EXT.

Stability and Diffusion Properties of Insulin in Dissolvable Microneedles: A Multiscale Simulation Study

Microneedle (MN) technology has been proven to be promising to become an effective drug delivery route of insulin for diabetes treatment, with the advantages of high delivery efficiency, convenient management, and minimal risk of infection. However, efforts are still required to verify the insulin activity in MNs for further clinical application. Moreover, it is also essential to study the diffusion properties of insulin to understand the ability of various MN materials to control insulin release. Herein, we have combined all-atom molecular dynamics simulation and coarse-grained dissipative particle dynamics to systematically study insulin's structural stability and diffusion coefficient in polyvinyl alcohol and hyaluronic acid solutions. The all-atom simulation reveals the dissimilarities in the interaction mode between insulin and the two polymers. It also points out that the presence of the two polymers would not irreversibly impact the secondary structure of insulin, thereby ensuring regular insulin expression in vivo. Mesoscopic simulation results manifest that the diffusion coefficient of insulin in hyaluronic acid (HA) solution is greater than that of the polyvinyl alcohol (PVA) system. Meanwhile, through the study of insulin centroid trajectory, we have claimed two different diffusion mechanisms of insulin in polymer solution: The movement of insulin in the HA and water solution follows the Brownian motion rule. In comparison, the hopping effect of insulin has been observed in the PVA solution due to poor intermolecular affinity as well as lower polymer water solubility. By summarizing different diffusion mechanisms, this study can provide theoretical guidance for preparing insulin-loaded dissolvable MNs.

Mesoscopic Simulation for the Effect of Cross-Linking Reactions on the Drug Diffusion Properties in Microneedles

The drug diffusion issue in microneedles is the focus of its medical application. It will not only affect the distribution of drugs in the needle body but will also have an impact on the drug release performance of the microneedle. The utilization of cross-linked polymer materials to obtain the drug diffusion control has been experimentally verified as a feasible method. However, the mechanism research on the molecular level is still incomplete. In this study, the dissipative particle dynamics (DPD) simulation has been applied to study the effect of the cross-linking reaction on drug diffusion in hyaluronic acid microneedles. We have discovered that when the cross-linking degree reaches 90%, the diffusion coefficient of the drug is 6.45 times lower than that of the uncross-linked system. The main reason for the decline in drug diffusion ability is that the cross-linking reaction varies the conformation of the polymer. The amplification in the cross-linking degree makes the polymer coils more compact and approach each other, finally forming a continuously distributed cross-linked network, which reduces its degradation rate in the body. Simultaneously, these cross-linked networks can also hinder the interaction of soluble drugs with water, thereby preventing the premature release of drugs. The simulation results are consistent with the data collected in the previous microneedle experiment. This work will be an extension of DPD simulation in the application of biological materials.

Translation of Polymeric Microneedles for Treatment of Human Diseases: Recent Trends, Progress, and Challenges

The ongoing search for biodegradable and biocompatible microneedles (MNs) that are strong enough to penetrate skin barriers, easy to prepare, and can be translated for clinical use continues. As such, this review paper is focused upon discussing the key points (e.g., choice polymeric MNs) for the translation of MNs from laboratory to clinical practice. The review reveals that polymers are most appropriately used for dissolvable and swellable MNs due to their wide range of tunable properties and that natural polymers are an ideal material choice as they structurally mimic native cellular environments. It has also been concluded that natural and synthetic polymer combinations are useful as polymers usually lack mechanical strength, stability, or other desired properties for the fabrication and insertion of MNs. This review evaluates fabrication methods and materials choice, disease and health conditions, clinical challenges, and the future of MNs in public healthcare services, focusing on literature from the last decade.

Active pharmaceutical ingredient poly(ionic liquid)-based microneedles for the treatment of skin acne infection

As an inflammatory skin disease of pilosebaceous follicles, Propionibacterium acnes (P. acnes) can aggravate local inflammatory responses and forms acne lesions. However, due to the skin barrier, various transdermal measures other than antibiotic creams are necessary. Microneedle (MN) patches are emerging platforms for the transdermal delivery of various therapeutics since it can effectively create transport pathways in the epidermis. Herein, we develop an active pharmaceutical ingredient poly(ionic liquid) (API PIL)-based MN patches containing salicylic acid (SA). The PIL-based MNs are simply prepared through photo-crosslinking of an imidazolium-type ionic liquid (IL) monomer in MN micro-molds, and following by anion exchange with salicylic acid anions (SA^-). The fabricated SA-loaded PIL-MNs exhibited therapeutic efficiency in the topical treatment of P. acnes infection in vitro and in vivo. These active pharmaceutical ingredient PIL-based MNs can improve acne treatment, demonstrating potential applications for skin diseases. STATEMENT OF SIGNIFICANCE: Microneedle (MN) patches can be used as platforms for transdermal delivery of various therapeutics to treat bacterial infection. Here, a facile strategy was developed to synthesize active pharmaceutical ingredient poly(ionic liquid)-based microneedle patches by anion-exchange with salicylic acid anion (SA^-). The fabricated SA-loaded PIL-MNs are active on not only anti-bacteria but also anti-inflammation in P. acnes treated mice, and may have potential applications for skin acne infection.