Preparation and Preliminary Evaluation of a Dissolving Microneedles Delivery System Based on Living Chlamydomonas reinhardtii

Background: Microalgae offer unique advantages in biomedicine due to their inherent biocompatibility, in situ photosynthetic oxygenation, and autonomous motility. Delivering them live and intact into subcutaneous tissue is crucial to actively ameliorate hypoxic lesion microenvironments and enhance tissue penetration. However, this efficient delivery is primarily hindered by the stratum corneum barrier. This study developed a novel composite platform integrating the biological functions of living microalgae with the transdermal delivery capabilities of dissolving microneedles (DMNs). Methods: Bioactive Chlamydomonas reinhardtii was cultured in TAP medium under a 16h:8h light-dark cycle. Using hyaluronic acid and polyvinylpyrrolidone (PVP K90) as the matrix, algae-loaded dMN arrays were fabricated via an optimized vacuum infiltration-centrifugation method. Array morphology, mechanical strength, and penetration capacity were evaluated using an in vitro Parafilm puncture model. Results: The fabrication process proved highly stable, yielding defect-free, regularly arranged conical dMN arrays. Mechanical testing demonstrated consistent strength, with the needles reliably penetrating three layers of Parafilm across multiple trials. The formulation successfully encapsulated the microalgae, preserved their viability, and exhibited the capacity to pierce the stratum corneum before rapidly dissolving in interstitial fluid to release the living cells. Conclusions: By encapsulating 36h-cultured microalgae within an optimized 400 mg/mL hyaluronic acid matrix via -0.07MPa vacuum and 4000 rpm centrifugation, this composite system achieved consistent penetration of a 3-layer simulated stratum corneum barrier under 2-minute compression. This "living-material" platform offers an innovative strategy for macromolecular or cell-level drug delivery and ameliorating hypoxic microenvironments at lesion sites, highlighting significant potential for clinical translation.