An annular corneal microneedle patch for minimally invasive ophthalmic drug delivery

Morphology Design and Precision Control of Microneedles by PμSL 3D Printing

Microneedles (MNs) hold significant potential for applications in transdermal drug delivery and biosensing. However, when traditional 3D printing technology is used for their manufacture, a substantial deviation in output size occurs. The effects of various parameters on the morphology of MNs produced through microscale 3D printing remain unclear. This study investigated the relationship between the design and fabrication of acrylic resin MNs and their output forms via a projection microstereolithography (PµSL) technology system. Modifying the shape parameters and array configurations elucidates the causes of size deviation and proposes a control strategy. This is particularly significant for the prototyping and mold manufacturing of MNs in relevant fields. This study indicates that a printing layer thickness of 10 µm optimally balances efficiency and clinical conversion requirements. Additionally, an exposure intensity of 65 mW/cm2 achieves both a high fidelity and an appropriate base size. The printing angle significantly influences the morphology and mechanical properties of MNs. The diameter and aspect ratio of solid MNs correlate with their dimensional stability. Clinically, conical or quadrilateral MNs with defined parameters are recommended. A critical spacing (≥40 µm) and an optimal arrangement of the MN arrays were established. The specific exposure intensity and vertical printing angle of the hollow MNs ensure the precision of the micropore diameter and wall thickness. This approach offers theoretical insights and process parameters essential for high-precision, customizable MN engineering design.

Microneedle-aided nanotherapeutics delivery and nanosensor intervention in advanced tissue regeneration

Microneedles (MNs) have been extensively used as transdermal therapeutics delivery devices since 1998 due to their capacity to penetrate physiological barriers with minimal invasiveness. Recent advances demonstrate the potential of MNs in improving diverse tissue regeneration when integrated with nanometer-sized therapeutics or sensors. This synergistic strategy can enhance drug delivery efficiency and therapeutic outcomes, and enable precise and personalized therapies through real-time monitoring of the repair process. In this review, we discuss how optimized MNs (through adjustments in geometry, material properties, and modular structure), when combined with dimension- and composition-specific nanomaterials, enhance tissue regeneration efficiency. Moreover, integrating stimuli-responsive nanotherapeutics or nanosensors into MNs for spatiotemporal-controlled and targeted drug release, physiotherapy effects, and intelligent monitoring is systematically outlined. Furthermore, we summarize therapeutic applications of nanotherapeutics-MN platforms in various soft and hard tissues, including skin, hair follicles (HF), cornea, joint, tendons, sciatic nerves, spinal cord, periodontium, oral mucosa, myocardium, endometrium, bone and intervertebral discs (IVD). Notably, recent attempts using nanosensor-MN platforms as smart wearable devices for monitoring damaged tissues via interstitial fluid (ISF) extraction and biomarker sensing are analyzed. This review potentially provides tissue regeneration practitioners/researchers with a cross-disciplinary perspective and inspiration.