Microneedle Mediated Transdermal Delivery of Protein, Peptide and Antibody Based Therapeutics: Current Status and Future Considerations

High-resolution two-photon polymerization: the most versatile technique for the fabrication of microneedle arrays

Microneedle patches have received much interest in the last two decades as drug/vaccine delivery or fluid sampling systems for diagnostic and monitoring purposes. Microneedles are manufactured using a variety of additive and subtractive micromanufacturing techniques. In the last decade, much attention has been paid to using additive manufacturing techniques in both research and industry, such as 3D printing, fused deposition modeling, inkjet printing, and two-photon polymerization (2PP), with 2PP being the most flexible method for the fabrication of microneedle arrays. 2PP is one of the most versatile and precise additive manufacturing processes, which enables the fabrication of arbitrary three-dimensional (3D) prototypes directly from computer-aided-design (CAD) models with a resolution down to 100 nm. Due to its unprecedented flexibility and high spatial resolution, the use of this technology has been widespread for the fabrication of bio-microdevices and bio-nanodevices such as microneedles and microfluidic devices. This is a pioneering transformative technology that facilitates the fabrication of complex miniaturized structures that cannot be fabricated with established multistep manufacturing methods such as injection molding, photolithography, and etching. Thus, microstructures are designed according to structural and fluid dynamics considerations rather than the manufacturing constraints imposed by methods such as machining or etching processes. This article presents the fundamentals of 2PP and the recent development of microneedle array fabrication through 2PP as a precise and unique method for the manufacture of microstructures, which may overcome the shortcomings of conventional manufacturing processes.

Development and characterisation of novel, enzymatically stable oxytocin analogues with beneficial antidiabetic effects in high fat fed mice

BACKGROUND

There is growing evidence to support beneficial effects of the hypothalamic synthesised hormone, oxytocin, on metabolism. However, the biological half-life of oxytocin is short and receptor activation profile unspecific.

METHODS

We have characterised peptide-based oxytocin analogues with structural modifications aimed at improving half-life and receptor specificity. Following extensive in vitro and in vivo characterisation, antidiabetic efficacy of lead peptides was examined in high fat fed (HFF) mice.

RESULTS

Following assessment of stability against enzymatic degradation, insulin secretory activity, receptor activation profile and in vivo bioactivity, analogues 2 N (Ac-C ^˂YIQNC ^>PLG-NH₂) and D7R ((d-C)YIQNCYLG-NH₂) were selected as lead peptides. Twice daily injection of either peptide for 22 days reduced body weight, energy intake, plasma glucose and insulin and pancreatic glucagon content in HFF mice. In addition, both peptides reduced total- and LDL-cholesterol, with concomitant elevations of HDL-cholesterol, and D7R also decreased triglyceride levels. The two oxytocin analogues improved glucose tolerance and insulin responses to intraperitoneal, and particularly oral, glucose challenge on day 22. Both oxytocin analogues enhanced insulin sensitivity, reduced HOMA-IR and increased bone mineral density. In terms of pancreatic islet histology, D7R reversed high fat feeding induced elevations of islet and beta cell areas, which was associated with reductions in beta cell apoptosis. Islet insulin secretory responsiveness was improved by 2 N, and especially D7R, treatment.

CONCLUSION

Novel, enzymatically stable oxytocin analogues exert beneficial antidiabetic effects in HFF mice.

GENERAL SIGNIFICANCE

These observations emphasise the, yet untapped, therapeutic potential of long-acting oxytocin-based agents for obesity and type 2 diabetes.

Recent advances on microneedle arrays-mediated technology in cancer diagnosis and therapy

Regarding the increasing prevalence of cancer throughout the globe, the development of novel alternatives for conventional therapies is inevitable to circumvent limitations such as low efficacy, complications, and high cost. Recently, microneedle arrays (MNs) have been introduced as a novel, minimally invasive, and low-cost approach. MNs can delivery both small molecule and macromolecular drugs or even nanoparticles (NPs) to the tumor tissue in a safe and controlled manner. Relying on the recent promising outcomes of MNs in transdermal delivery of anticancer agents, this review is aimed to summarize constituent materials, fabrication methods, advantages, and limitations of different types of MNs used in cancer therapy applications. This review paper also presents the potential use of MNs in transdermal delivery of NPs for effective chemotherapy, gene therapy, immunotherapy, photodynamic, and photothermal therapy. Additionally, MNs are currently explored as routine point-of-care health monitoring devices for transdermal detection of cancer biomarkers or physiologically relevant analytes which will be addressed in this paper. Despite the promising potential of MNs for cancer therapy and diagnosis, several limitations have impeded their therapeutic efficacy and real-time applicability that are addressed in this paper.