High-Strength Smart Microneedles with "Offensive and Defensive" Effects for Intervertebral Disc Repair.

Intervertebral disc degeneration (IVDD) is a global public health issue. The injury of annulus fibrosus (AF) caused by acupuncture or discectomy can trigger IVDD again. However, there is currently no suitable method for treating AF injury. In this study, w e developed the high-strength smart microneedles (MNs) which can penetrate the AF tissue through a local and minimally invasive method, and achieve remote control of speeded-up release of the drug and hyperthermia by the Near Infrared. The PDA/GelMA composite MNs loaded with diclofenac sodium w ere designed to extracellularly "offend" the inflammatory microenvironment and mitigate damage to cells, and intracellularly increase the level of cytoprotective heat shock proteins to enhance the defense against the hostile microenvironment, achieving "offensive and defensive" effects. In vitro experiments demonstrated that the synergistic treatment of photothermal therapy and anti-inflammation effectively reduced inflammation, inhibited cell apoptosis, and promoted the synthesis of the extracellular matrix (ECM). In vivo experiments showed that the MNs mitigated the inflammatory response, promoted ECM deposition, reduced the level of apoptosis, and restored the biomechanical properties of the intervertebral disc (IVD) in rats. Overall, this high-strength smart MNs displayed promising "offensive and defensive" effects that can provide a new strategy for IVD repair. This article is protected by copyright. All rights reserved.