The promising application of hydrogel microneedles in medical application

OBJECTIVES

Hydrogel microneedles are emerging, and promising microneedles mainly composed of swelling polymers. This review is intended to summarize the preparation materials, formation mechanisms, applications and existing problems of hydrogel microneedles.

METHODS

We collected the literature on the materials, preparation and application of hydrogel microneedles in recent years, and summarized their mechanism and application in drugs delivery.

KEY FINDINGS

Hydrogel microneedles have higher safety and capabilities of controlled drug release, and have been mainly used in tumour and diabetes treatment, as well as clinical monitoring. In recent years, hydrogel microneedles have shown great potential in drug delivery, and have played the role of whitening, anti-inflammatory and promoting healing.

CONCLUSIONS

As an emerging drug delivery idea, hydrogel microneedles for drug delivery has gradually become a research hotspot. This review will provide a systematic vision for the favourable development of hydrogel microneedles and their promising application in medicine, especially drug delivery.

Skin Patchable Sensor Surveillance for Continuous Glucose Monitoring

Diabetes mellitus is a physiological and metabolic disorder affecting millions of people worldwide, associated with global morbidity, mortality, and financial expenses. Long-term complications can be avoided by frequent, continuous self-monitoring of blood glucose. Therefore, this review summarizes the current state-of-art glycemic control regimes involving measurement approaches and basic concepts. Following an introduction to the significance of continuous glucose sensing, we have tracked the evolution of glucose monitoring devices from minimally invasive to non-invasive methods to present an overview of the spectrum of continuous glucose monitoring (CGM) technologies. The conveniences, accuracy, and cost-effectiveness of the real-time CGM systems (rt-CGMs) are the factors considered for discussion. Transdermal biosensing and drug delivery routes have recently emerged as an innovative approach to substitute hypodermal needles. This work reviews skin-patchable glucose monitoring sensors for the first time, providing specifics of all the major findings in the past 6 years. Skin patch sensors and their progressive form, i.e., microneedle (MN) array sensory and delivery systems, are elaborated, covering self-powered, enzymatic, and non-enzymatic devices. The critical aspects reviewed are material design and assembly techniques focusing on flexibility, sensitivity, selectivity, biocompatibility, and user-end comfort. The review highlights the advantages of patchable MNs' multi-sensor technology designed to maintain precise blood glucose levels and administer diabetes drugs or insulin through a "sense and act" feedback loop. Subsequently, the limitations and potential challenges encountered from the MN array as rt-CGMs are listed. Furthermore, the current statuses of working prototype glucose-responsive "closed-loop" insulin delivery systems are discussed. Finally, the expected future developments and outlooks in clinical applications are discussed.

Biocompatible All-in-One Adhesive Needle-Free Cup Patch for Enhancing Transdermal Drug Delivery

Patch-type drug delivery has garnered increased attention as an attractive alternative to the existing drug delivery techniques. Thus far, needle phobia and efficient drug delivery remain huge challenges. To address the issue of needle phobia and enhance drug delivery, we developed a needle-free and self-adhesive microcup patch that can be loaded with an ultrathin salmon DNA (SDNA) drug carrier film. This physically integrated system can facilitate efficient skin penetration of drugs loaded into the microcup patch. The system consists of three main components, namely, a cup that acts as a drug reservoir, an adhesive system that attaches the patch to the skin, and physical stimulants that can be used to increase the efficiency of drug delivery. In addition, an ultrathin SDNA/drug film allows the retention of the drug in the cup and its efficient release by dissolution in the presence of moisture. This latter feature has been validated using gelatin as a skin mimic. The cup design itself has been validated by comparing its deformation and displacement with those of a cylindrical structure. Integration of the self-adhesive microcup patch with both ultrasonic waves and an electric current allows the model drug to penetrate the stratum corneum of the skin barrier and the whole epidermis, thereby enhancing transdermal drug delivery and reducing skin irritation. This system can be used as a wearable biomedical device for efficient transdermal and needle-free drug delivery.