Effect of Surface Interactions on Microsphere Loading in Dissolving Microneedle Patches

Fabrication of lidocaine-loaded polymer dissolving microneedles for rapid and prolonged local anesthesia

There is an urgent need for research into effective interventions for pain management to improve patients' life quality. Traditional needle and syringe injection were used to administer the local anesthesia. However, it causes various discomforts, ranging from brief stings to trypanophobia and denial of medical operations. In this study, a dissolving microneedles (MNs) system made of composite matrix materials of polyvinylpyrrolidone (PVP), polyvinyl alcohol (PVA), and sodium hyaluronate (HA) was successfully developed for the loading of lidocaine hydrochloride (LidH). The morphology, size and mechanical properties of the MNs were also investigated. After the insertion of MNs into the skin, the matrix at the tip of the MNs was swelled and dissolved by absorption of interstitial fluid, leading to a rapid release of loaded LidH from MNs' tips. And the LidH in the back patching was diffused into deeper skin tissue through microchannels created by MNs insertion, forming a prolonged anesthesia effect. In addition, the back patching of MNs could be acted as a drug reservoir to form a prolonged local anesthesia effect. The results showed that LidH MNs provided a superior analgesia up to 8 h, exhibiting a rapid and long-lasting analgesic effects. Additionally, tissue sectioning and in vitro cytotoxicity tests indicated that the MNs patch we developed had a favorable biosafety profile.

A sound-absorbing and heat-insulating collagen fiber composite material

Using methacrylic acid (MAA) and methyl methacrylate (MMA) as core monomers and polystyrene as the shell layer, polymer hollow microspheres (PHM) with good stability were prepared by using an alkali osmotic swelling method followed by spray drying. The average size of the PHM was approximately 875 nm. As a filling cross-linking agent, the PHM were added to a skin collagen material to disperse and fix, and a “polymer hollow microsphere composite collagen fiber” (PHCC) material was obtained. The results show that the PHM improve the mechanical strength, thermal stability and water resistance of the skin collagen material. The PHCC material has a low thermal conductivity (0.035 W/(K·m)) and excellent sound insulation performance and retains the soft and delicate touch of leather, which has application value in high-grade decorative materials and functional leather. This provides a new approach for developing flexible sound-absorbing thermal insulation materials.