Skin optical clearing enabled by dissolving hyaluronic acid microneedle patches.

Optical imaging and phototherapy are of great significance in the detection, diagnosis, and therapy of diseases. Depth of light in the skin tissues in optical imaging and phototherapy can be significantly improved with the assistance of optical clearing technology by weakening the scattering from the refractive indexes inhomogeneity among skin constituents. However, the barrier of the stratum corneum restricts the penetration of optical clearing agents into deep tissues and limits the optical clearing effects. Herein, we develop an optical clearing strategy by using dissolving microneedle (MN) patches made of hyaluronic acid (HA), which can effortlessly and painlessly penetrate the stratum corneum to reach the epidermis and dermis. By using the HA MN patches, the transmittance of skin tissues is improved by about 12.13 %. We show that the HA MN patches enhance the clarity of blood vessels to realize naked-eyes observation. Moreover, a simulated subcutaneous tumor cells experiment also verifies that the optical clearing effects of the HA MN patch efficiently boost the efficiency of the photodynamic killing of tumor cells by 26.8 %. As a courageous attempt, this study provides a promising avenue to improve the optical clearing effects for further clinical application of optical imaging and phototherapy.

Microfluidics-assisted optimization of highly adhesive haemostatic hydrogel coating for arterial puncture.

Although common in clinical practice, bleeding after tissue puncture may cause serious outcomes, especially in arterial puncture. Herein, gelatin-tannic acid composite hydrogels with varying compositions are prepared, and their adhesive properties are further optimized in microfluidic channel-based simulated vessels for haemostasis in arterial puncture. It is revealed that the composite hydrogels on the syringe needles used for arterial puncture should possess underwater adhesion higher than 4.9 kPa and mechanical strength higher than 86.0 kPa. The needles coated with the gelatin-tannic acid composite hydrogel completely prevent blood loss after both vein and arterial puncture in different animal models. This study holds great significance for the preparation of haemostatic needles for vessel puncture, and gelatin-tannic acid hydrogel coated needles may help to prevent complications associated with arterial puncture.