Microneedle (MN)-assisted drug delivery technology has gained increasing attention over the past two decades. Its advantages of self-management and being minimally invasive could allow this technology to be an alternative to hypodermic needles. MNs can penetrate the stratum corneum and deliver active ingredients to the body through the dermal tissue in a controlled and sustained release. Long-acting polymeric MNs can reduce administration frequency to improve patient compliance and therapeutic outcomes, especially in the management of chronic diseases. In addition, long-acting MNs could avoid gastrointestinal reactions and reduce side effects, which has potential value for clinical application. In this paper, advances in design strategies and applications of long-acting polymeric MNs are reviewed. We also discuss the challenges in scale manufacture and regulations of polymeric MN systems. These two aspects will accelerate the effective clinical translation of MN products.

Engineered circular RNAs (circRNAs) are a class of single-stranded RNAs with head-to-tail covalently linked structures that integrate open reading frames (ORFs) and internal ribosome entry sites (IRESs) with the function of coding and expressing proteins. Compared to mRNA vaccines, circRNA vaccines offer a more improved method that is safe, stable, and simple to manufacture. With the rapid revelation of the biological functions of circRNA and the success of Severe Acute Respiratory Coronavirus Type II (SARS-CoV-2) mRNA vaccines, biopharmaceutical companies and researchers around the globe are attempting to develop more stable circRNA vaccines for illness prevention and treatment. Nevertheless, research on circRNA vaccines is still in its infancy, and more work and assessment are needed for their synthesis, delivery, and use. In this review, based on the current understanding of the molecular biological properties and immunotherapeutic mechanisms of circRNA, we summarize the current preparation methods of circRNA vaccines, including design, synthesis, purification, and identification. We discuss their delivery strategies and summarize the challenges facing the clinical application of circRNAs to provide references for circRNA vaccine-related research.

Large-scale infectious diseases have become a significant threat to human health and safety. The successful invention of vaccines is the most powerful means for preventing infectious diseases and has greatly improved global human health. Even during the pandemic of COVID-19, which has affected the world, vaccines have played an irreplaceable role. Microneedles (MNs) punctured the stratum corneum and formed microchannels in the skin allowing the vaccine to be efficiently recognized by the abundant antigen-presenting cells (APCs) in the skin to form specific immunity. Compared with traditional vaccination methods, MN transdermal immunization has the advantages of painlessness, easy storage, and efficient immune response. In this review, we summarize the types of vaccines, types of MNs, research progress and clinical research status of MN-based vaccines. We also cover various technologies for vaccine encapsulation, stable delivery of MN vaccines, and a wide range of potential clinical applications. We also outline the future development prospects of the MN system onboard to achieve better clinical benefits.

There is an error in the Funding statement. The correct number for the Natural Science Foundation of Shandong Province, China is ZR2022QB149. The authors apologize for this error and state that this does not change the scientific conclusions of the article in any way. The original article has been updated.