Exploring new frontiers in drug delivery with minimally invasive microneedles: fabrication techniques, biomedical applications and regulatory aspects

Enhanced transdermal delivery of pioglitazone hydrochloride via conductive hydrogel microneedles combined with iontophoresis

The conventional oral administration of pioglitazone for Type II diabetes management is frequently compromised by hepatic first-pass metabolism and associated systemic adverse effects, necessitating the development of enhanced transdermal delivery approaches. This study developed a transdermal drug delivery system combining conductive hydrogel microneedles and iontophoresis to improve the transdermal delivery of pioglitazone hydrochloride (PIO) and its therapeutic efficacy in the treatment of type II diabetes. The microneedles, fabricated using poly(methyl vinyl ether-alt-maleic anhydride) as the main matrix material, exhibited excellent conductivity, mechanical strength, and high drug loading capacity. In vitro permeation experiments demonstrated that, when combined with iontophoresis at a current intensity of 0.5 mA, the cumulative permeation of PIO reached 238.1 ± 27.14 μg/cm2 within 48 h, significantly higher than that of the microneedle group alone. In a type II diabetic rat model, the microneedle-iontophoresis system displayed a significantly better hypoglycemic effect than the oral administration group, with a blood glucose reduction of 6.3 mmol/L on day 8, significantly higher than the 5.1 mmol/L reduction in the positive control group. Pharmacokinetic analysis indicated that the Tmax, T1/2, and mean residence time of the system were longer than those of oral administration, indicating sustained-release characteristics. Skin irritation tests revealed that the system caused only mild, transient skin irritation, with complete skin recovery within 24 h. In conclusion, conductive hydrogel microneedles combined with iontophoresis can effectively enhance PIO transdermal delivery, bioavailability, and therapeutic efficacy while also exhibiting good safety and potential clinical application value.

Polymeric microneedle advancements in macromolecule drug delivery: current trends, challenges, and future perspectives

Microneedles (MNs) offer a transformative solution for delivering macromolecules, including proteins, RNA, and peptides. These are critical in treating complex diseases but face significant challenges such as immunogenicity, poor stability, high molecular weight, and delivery efficiency. Unlike conventional methods, MNs efficiently bypass biological barriers like the stratum corneum, enabling precise and minimally invasive transdermal drug delivery. This review explores various MN types such as solid, coated, hollow, hydrogel-forming, and dissolving and their therapeutic applications in cancer immunotherapy, diabetes management, and osteoporosis treatment. For instance, dissolving MNs have been employed for transdermal insulin delivery, enhancing patient compliance and therapeutic outcomes. Similarly, hydrogel MNs have shown promise in sustained drug release for immunotherapy applications. By addressing cost and scalability issues, polymeric MNs demonstrate significant potential for clinical translation, paving the way for innovations in macromolecule delivery, diagnostics, and personalised medicine. This review underscores the pivotal role of MNs in redefining drug delivery systems, offering improved efficacy, patient comfort, and accessibility.

Transdermal delivery of PeptiCRAd cancer vaccine using microneedle patches

Microneedles (MNs) are a prospective system in cancer immunotherapy to overcome barriers regarding proper antigen delivery and presentation. This study aims at identifying the potential of MNs for the delivery of Peptide-coated Conditionally Replicating Adenoviruses (PeptiCRAd), whereby peptides enhance the immunogenic properties of adenoviruses presenting tumor associated antigens. The combination of PeptiCRAd with MNs containing polyvinylpyrrolidone and sucrose was tested for the preservation of structure, induction of immune response, and tumor eradication. The findings indicated that MN-delivered PeptiCRAd was effective in peptide presentation in vivo, leading to complete tumor rejection when mice were pre-vaccinated. A rise in the cDC1 population in the lymph nodes of the MN treated mice led to an increase in the effector memory T cells in the body. Thus, the results of this study demonstrate that the combination of MN technology with PeptiCRAd may provide a safer, more tolerable, and efficient approach to cancer immunotherapy, potentially translatable to other therapeutic applications.

What Is the Optimal Geometry of Dissolving Microneedle Arrays? A Literature Review

The application of dissolving microneedle arrays (DMNAs) is an emerging trend in drug and vaccine delivery as an alternative for hypodermic needles or other less convenient drug administration methods. The major benefits include, amongst others, that no trained healthcare personnel is required and that the recipient experiences hardly any pain during administration. However, for a successful drug or vaccine delivery from the DMNA, the microneedles should be inserted intact into the skin. A successful penetration into the upper skin layers may be challenging because of the elastic nature of the skin; therefore, a minimum insertion force is required to overcome the total resistance force of the skin. In addition, the microneedles need to stay intact, which requires a certain mechanical strength, and be able to resist the required insertion force. In addition to the type of material with which the DMNAs are produced, the geometry of the DMNAs will also have a profound effect, not only on the mechanical strength but also on the number of insertions and penetration depth into the skin. In this review, the effects of shape, aspect ratio, length, width of the base, tip diameter and angle, and spacing of DMNAs on the aforementioned effect parameters were evaluated to answer the following question: 'What is the optimal geometry of dissolving microneedle arrays?'.

Therapeutic Potential of Microneedle Assisted Drug Delivery for Wound Healing: Current State of the Art, Challenges, and Future Perspective

Microneedles (MNs) appear as a transformative and minimally invasive platform for transdermal drug delivery, representing a highly promising strategy in wound healing therapeutics. This technology, entailing the fabrication of micron-scale needle arrays, enables the targeted and efficient delivery of bioactive agents into the epidermal and dermal layers without inducing significant pain or discomfort. The precise penetration of MNs facilitates localized and sustained drug release, which significantly enhances tissue regeneration and accelerates wound closure. Furthermore, MNs can be engineered to encapsulate essential bioactive compounds, including antimicrobial agents, growth factors, and stem cells, which are critical for modulating the wound healing cascade and mitigating infection risk. The biodegradable nature of these MNs obviates the need for device removal, rendering them particularly advantageous in the management of chronic wounds such as diabetic ulcers and pressure sores. The integration of nanotechnology within MNs further augments their drug-loading capacity, stability, and controlled-release kinetics, offering a sophisticated therapeutic modality. This cutting-edge approach has the potential to redefine wound care by optimizing therapeutic efficacy, reducing adverse effects, and enhancing patient adherence. As MN technology advances, its application in wound healing exemplifies a dynamic frontier within biomedical engineering and regenerative medicine.

Recent progress in the 3D printing of microneedle patches for biomedical applications

3D-printed microneedles (MNs) have emerged as a transformative technology in drug delivery, diagnostics, and cosmetics, providing a minimally invasive alternative to traditional methods. This review highlights the advancements in 3D printing technologies, including fused deposition modeling (FDM), digital light processing (DLP), and stereolithography (SLA), which enable the precise fabrication of MNs with customizable geometries and functionalities. The unique ability of MNs to penetrate the stratum corneum facilitates enhanced delivery of therapeutic agents, biosensing capabilities, and improved patient compliance. Recent innovations in MNs design, such as biomimetic structures and optimized geometries, have significantly improved their mechanical properties and drug delivery efficiency. Furthermore, integrating sensing elements within MNs enables real-time monitoring of biomarkers, paving the way for personalized medicine. Despite the promising applications, challenges remain, including regulatory considerations, material biocompatibility, and manufacturing scalability. This review discusses the current state of 3D-printed MNs, their diverse applications, and future directions. By addressing existing limitations and exploring novel materials and hybrid fabrication techniques, 3D-printed MNs have the potential to revolutionize healthcare delivery and improve patient outcomes.

Microneedle system for tissue engineering and regenerative medicines: a smart and efficient therapeutic approach

The global demand for an enhanced quality of life and extended lifespan has driven significant advancements in tissue engineering and regenerative medicine. These fields utilize a range of interdisciplinary theories and techniques to repair structurally impaired or damaged tissues and organs, as well as restore their normal functions. Nevertheless, the clinical efficacy of medications, materials, and potent cells used at the laboratory level is always constrained by technological limitations. A novel platform known as adaptable microneedles has been developed to address the abovementioned issues. These microneedles offer a solution for the localized distribution of various cargos while minimizing invasiveness. Microneedles provide favorable patient compliance in clinical settings due to their effective administration and ability to provide a painless and convenient process. In this review article, we summarized the most recent development of microneedles, and we started by classifying various microneedle systems, advantages, and fundamental properties. Subsequently, it provides a comprehensive overview of different types of microneedles, the material used to fabricate microneedles, the fundamental properties of ideal microneedles, and their applications in tissue engineering and regenerative medicine, primarily focusing on preserving and restoring impaired tissues and organs. The limitations and perspectives have been discussed by concluding their future therapeutic applications in tissue engineering and regenerative medicines.

Recent progress of polymeric microneedle-assisted long-acting transdermal drug delivery

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.