Metal Microneedles Research Articles

A biodegradable lipid nanoparticle delivers a Cas9 ribonucleoprotein for efficient and safe in situ genome editing in melanoma

The development of melanoma is closely related to Braf gene, which is a suitable target for CRISPR/Cas9 based gene therapy. CRISPR/Cas9-sgRNA ribonucleoprotein complexes (RNPs) stand out as the safest format compared to plasmid and mRNA delivery. Similarly, lipid nanoparticles (LNPs) emerge as a safer alternative to viral vectors for delivering the CRISPR/Cas9-sgRNA gene editing system. Herein, we have designed multifunctional cationic LNPs specifically tailored for the efficient delivery of Cas9 RNPs targeting the mouse Braf gene through transdermal delivery, aiming to treat mouse melanoma. LNPs are given a positive charge by the addition of a newly synthesized polymer, deoxycholic acid modified polyethyleneimine (PEI-DOCA). Positive charge enables LNPs to be delivered in vivo by binding to negatively charged cell membranes and proteins, thereby facilitating efficient skin penetration and enhancing the delivery of RNPs into melanoma cells for gene editing purposes. Our research demonstrates that these LNPs enhance drug penetration through the skin, successfully delivering the Cas9 RNPs system and specifically targeting the Braf gene. Cas9 RNPs loaded LNPs exert a notable impact on gene editing in melanoma cells, significantly suppressing their proliferation. Furthermore, in mice experiments, the LNPs exhibited skin penetration and tumor targeting capabilities. This innovative LNPs delivery system offers a promising gene therapy approach for melanoma treatment and provides fresh insights into the development of safe and effective delivery systems for Cas9 RNPs in vivo. STATEMENT OF SIGNIFICANCE: CRISPR/Cas9 technology brings new hope for cancer treatment. Cas9 ribonucleoprotein offers direct genome editing, yet delivery challenges persist. For melanoma, transdermal delivery minimizes toxicity but faces skin barrier issues. We designed multifunctional lipid nanoparticles (LNPs) for Cas9 RNP delivery targeting the Braf gene. With metal microneedle pretreatment, our LNPs effectively edited melanoma cells, reducing Braf expression and inhibiting tumor growth. Our study demonstrates LNPs' potential for melanoma therapy and paves the way for efficient in vivo Cas9 RNP delivery systems in cancer therapy.

From microchips to microneedles: semiconductor shear testers as a universal solution for transverse load analysis of microneedle mechanical performance

Abstract Microneedles are a promising technology for pain-free and efficient pharmaceutical delivery. However, their clinical translation is currently limited by the absence of standardized testing methods for critical quality attributes (CQAs), such as mechanical robustness, which are essential for demonstrating safety and efficacy during regulatory review. A key aspect of mechanical robustness is transverse load capacity, which is currently assessed using diverse, non-standardized methods, which have limited capability to measure transverse failure forces at different heights along a microneedle. This is critical for understanding mechanics of potential failure modes during insertion after skin penetration. In this work we utilize a wire bond shear tester, a piece of test equipment widely used in the semiconductor industry, to measure the transverse load capacities of various microneedle designs. This approach is compatible with diverse microneedle types, geometries, and materials, and offers high-throughput and automated testing capabilities with high precision. We measure transverse failure loads with micron-scale control over the test height and have established comprehensive profiles of mechanical robustness along the length of different microneedle designs, which is a capability not previously demonstrated in literature for polymeric and metal microneedles. Transverse failure forces were 10±0.3 gf to 128±12 gf for wire bonded gold and silver microneedles, 11±0.7 gf to 480±69 gf for conical and pyramidal polymeric microneedles, and 206±80 gf to 381±1 gf for 3D printed conical stainless steel microneedles. Additionally, we present standardized definitions for microneedle structural failure modes resulting from transverse loads, which can facilitate root cause failure analysis and defect detection during design and manufacturing, and aid in risk assessment of microneedle products. This work establishes a standardized approach to evaluating a significant CQA of microneedle products, which is a critical step towards expediting their clinical adoption.

Direct Printing of High-Resolution Metallic Three-Dimensional Microneedle Arrays Via Electrohydrodynamic Jet Printing

Abstract Three-dimensional (3D) microneedle arrays (MAs) have shown remarkable performances for a wide range of biomedical applications. Achieving advanced customizable 3D MAs for personalized research and treatment remain a formidable challenge. In this paper, we have developed a high-resolution electrohydrodynamic (EHD) 3D printing process for fabricating customizable 3D MAs with economical and biocompatible molten alloy. The critical printing parameters (i.e., voltage and pressure) on the printing process for both two-dimensional (2D) and 3D features are characterized, and an optimal set of printing parameters was obtained for printing 3D MAs. We have also studied the effect of the tip-nozzle separation speed on the final tip dimension, which will directly influence MAs' insertion performance and functions. With the optimal process parameters, we successfully EHD printed customizable 3D MAs with varying spacing distances and shank heights. A 3 × 3 customized 3D MAs configuration with various heights ranging from 0.8 mm to 1 mm and a spacing distance as small as 350 μm were successfully fabricated, in which the diameter of each individual microneedle was as small as 100 μm. A series of tests were conducted to evaluate the printed 3D MAs. The experimental results demonstrated that the printed 3D MAs exhibit good mechanical strength for implanting and good electrical properties for electrophysiological sensing and stimulation. All results show the potential applications of the EHD printing technique in fabricating cost-effective, customizable, high-performance MAs for biomedical applications.

A study on the fabrication of metal microneedle array electrodes for ECG detection based on low melting point Bi–In–Sn alloys

This study describes the fabrication and characteristics of microneedle array electrodes (MAEs) using Bismuth–Indium–Tin (Bi–In–Sn) alloys. The MAEs consist of 57 pyramid-shaped needles measuring 340 μm wide and 800 μm high. The fabrication process involved micromolding the alloys in a vacuum environment. Physical tests demonstrated that Bi–In–Sn MAEs have good mechanical strength, indicating their suitability for successful skin penetration. The electrode–skin interface impedance test confirmed that Bi–In–Sn MAEs successfully penetrated the skin. Impedance measurements revealed the importance of insulating the microneedle electrodes for optimal electrical performance, and a UV-curable Polyurethane Acrylate coating was applied to enhance insulation. Electrocardiogram measurements using the Bi–In–Sn MAEs demonstrated performance comparable to that of traditional Ag/AgCl electrodes, which shows promise for accurate data collection. Overall, the study demonstrates successful, minimally-invasive skin insertion, improved electrical insulation, and potential applications of Bi–In–Sn microneedle array. These findings contribute to advancements in microneedle technology for biomedical applications.

Antimicrobial Evaluation of Metal Microneedles Made by Local Electrodeposition-Based Additive Manufacturing on Metal-Coated Substrates

Antimicrobial Evaluation of Metal Microneedles Made by Local Electrodeposition-Based Additive Manufacturing on Metal-Coated Substrates

Polymeric Microneedles: An Emerging Paradigm for Advanced Biomedical Applications

Microneedles are gaining popularity as a new paradigm in the area of transdermal drug delivery for biomedical and healthcare applications. Efficient drug delivery with minimal invasion is the prime advantage of microneedles. The concept of the microneedle array provides an extensive surface area for efficient drug delivery. Various types of inorganics (silicon, ceramic, metal, etc.) and polymeric materials are used for the fabrication of microneedles. The polymeric microneedles have various advantages over other microneedles fabricated using inorganic material, such as biocompatibility, biodegradation, and non-toxicity. The wide variety of polymers used in microneedle fabrication can provide a broad scope for drug delivery and other biomedical applications. Multiple metallic and polymeric microneedles can be functionalized by polymer coatings for various biomedical applications. The fabrication of polymeric microneedles is shifting from conventional to advanced 3D and 4D printing technology. The multifaceted biomedical applications of polymeric microneedles include drug delivery, vaccine delivery, biosensing, and diagnostic applications. Here, we provide the overview of the current and advanced information on polymers used for fabrication, the selection criteria for polymers, biomedical applications, and the regulatory perspective of polymer-based and polymer-coated microneedles, along with a patent scenario.

Wearable, Self‐powered, Drug‐Loaded Electronic Microneedles for Accelerated Tissue Repair of Inflammatory Skin Disorders

AbstractElectrical stimulation (ES) is widely used in physiological and medical sciences, while its application to treat inflammatory skin diseases (ISDs) remains a challenge owing to their natural pathological cuticle barrier and lack of an effective combination with chemotherapy to achieve specific immunomodulation. Here, a wearable, battery‐free, multi‐component drug‐loaded electronic microneedle (mD‐eMN) system is developed by integrating remodeled metal microneedles loaded with multi‐component chemical drugs and flexible triboelectric nanogenerators (TENGs). The system can rapidly release drugs into the site of ISDs and then realize an efficient penetration into cell body and specific immunomodulation under the synergism of pulsed electrons originating from the TENG. Also, the pulsed electrons can promote skin tissue homeostasis reconstruction to alleviate the inflammatory process of ISDs. Sufficient evidence shows that a significant skin inflammation regression of psoriasis (a typical ISDs model) is achieved using the mD‐eMN system compared to traditional ES or chemotherapy alone. This innovative wearable mD‐eMN system provides an effective flexible electronic and chemical drug joint technological platform for the treatment of ISDs, which is not only suitable for the treatment of psoriasis in this study but also maybe for other ISDs such as diabetic ulcers and skin tumors.

PEDOT coated microneedles towards electrochemically assisted skin sampling.

Skin sampling is a diagnostic procedure based on the analysis of extracted skin tissues and/or the observation of biomarkers in bodily fluids. Sampling using microneedles (MNs) that minimize invasiveness is gaining attention over conventional biopsy/blood lancet. In this study, new MNs for electrochemically assisted skin sampling are reported, specifically tailored for combined skin tissue biopsy and interstitial fluid (ISF) extraction. To overcome risks associated with using metal MNs, a highly electroactive, mechanically flexible, and biocompatible organic conducting polymer (CP) coated onto plastic is chosen as an alternative. Two different variants of doped poly(3,4-ethylenedioxythiophene) are coated on polymethyl methacrylate and used in combination as a MN pair with subsequent testing via a variety of electrochemical techniques to (i) give real-time information of the MN penetration depth into the skin, and (ii) yield new information on various salts present in the ISF. The MN skin sampler shows the ability to extract ions from the hydrated excised skin as a step towards in vivo ISF extraction. The presence of ions was analyzed using X-ray photoelectron spectroscopy. This added chemical information in conjunction with the existing biomarker analysis increases opportunity for disease/condition detection. For example, in the case of psoriasis, information about salt in the skin is invaluable in combination with pathogenic gene expression for diagnosis.

Biodegradable Mg Electrodes for Iontophoretic Transdermal Drug Delivery

Biodegradable metals have received limited attention for application in transdermal drug delivery, although metallic microneedles (MNs) and iontophoresis have been thoroughly researched for this purpose. Here, we present Mg as a salient candidate for an MN electrode. Its metallic properties enable the application of voltage to enhance the diffusion of charged drug molecules, while hydrogen gas generated during Mg corrosion prevents its application to electrodes. The Mg MN electrode was fabricated using a nanosecond laser, and the amount of hydrogen gas were measured with applied potential during iontophoresis. Accordingly, an appropriate potential window for iontophoresis was established based on the combined effect of enhanced drug diffusion by applied electric potential and impediment from hydrogen generation. The dye permeation tests of the Mg MN on the porcine skin demonstrated the combined effect of the Mg MN and iontophoresis. The dye migration decreased at higher voltages due to excess hydrogen generation and the corrosion of needle tips, both making the diffusion of charged dye molecules along the Mg MN surface harder. These results demonstrate optimal potential range of Mg MN electrodes for transdermal drug delivery with an electric field and bubble generation during iontophoresis.Graphical

Metallic Microneedles for Transdermal Drug Delivery: Applications, Fabrication Techniques and the Effect of Geometrical Characteristics.

Current procedures for transdermal drug delivery (TDD) have associated limitations including poor administration of nucleic acid, small or large drug molecules, pain and stress for needle phobic people. A painless micro-sized device capable of delivering drugs easily and efficiently, eliminating the disadvantages of traditional systems, has yet to be developed. While polymeric-based microneedle (MN) arrays have been used successfully and clinically as TDD systems, these devices lack mechanical integrity, piercing capacity and the ability to achieve tailored drug release into the systemic circulation. Recent advances in micro/nano fabrication techniques using Additive Manufacturing (AM), also known as 3D printing, have enabled the fabrication of metallic MN arrays, which offer the potential to overcome the limitations of existing systems. This review summarizes the different types of MNs used in TDD and their mode of drug delivery. The application of MNs in the treatment of a range of diseases including diabetes and cancer is discussed. The potential role of solid metallic MNs in TDD, the various techniques used for their fabrication, and the influence of their geometrical characteristics (e.g., shape, size, base diameter, thickness, and tip sharpness) on effective TDD are explored. Finally, the potential and the future directions relating to the optimization of metallic MN arrays for TDD are highlighted.

High density cleanroom-free microneedle arrays for pain-free drug delivery

The purpose of this work is to demonstrate the fabrication process for cleanroom-free solid metal microneedles and perform quantification of insertion profiles. Metal microneedles were created using a modified wirebonding process and inserted into porcine tissue to determine design efficacy. Microneedle arrays were analyzed through optical imaging and scanning electron microscopy. Insertion forces were measured using combined uniaxial load cell and resistance measurement data. Microneedle arrays were successfully inserted into porcine tissue with high repeatability and reliability. These arrays demonstrate lower or equivalent insertion forces (less than 3 N) to other forms of microneedles in the literature without the need for complex cleanroom fabrication processes. The microneedle fabrication method presented here rapidly produces mass manufacturable, high-quality microneedle arrays with minimal insertion forces, able to reliably penetrate tissue samples. The manufacturing method presented here achieved array densities as high as 3200 needles cm−2. These microneedle arrays demonstrate simple fabrication of a reliable, high-density, pain-free drug delivery system, with potential applications in biosensing and electric field modulated drug delivery.

Fabrication of Polymeric Microneedles using Novel Vacuum Compression Molding Technique for Transdermal Drug Delivery.

To demonstrate the feasibility of vacuum compression molding as a novel technique for fabricating polymeric poly (D, L-lactic-co-glycolic acid) microneedles. First, polydimethylsiloxane molds were prepared using metal microneedle templates and fixed in the MeltPrep® Vacuum Compression Molding tool. Poly (D, L-lactic-co-glycolic acid) (EXPANSORB® DLG 50-5A) was added, enclosed, and heated at 130°C for 15 min under a vacuum of -15 psi, cooled with compressed air for 15 min, followed by freezing at -20°C for 30 min, and stored in a desiccator. The microneedles and microchannels were characterized by a variety of imaging techniques. In vitro permeation of model drug lidocaine as base and hydrochloride salt was demonstrated across intact and microporated dermatomed human skin. Fabricated PLGA microneedles were pyramid-shaped, sharp, uniform, and mechanically robust. Scanning electron microscopy, skin integrity, dye-binding, histology, and confocal laser microscopy studies confirmed the microchannel formation. The receptor delivery of lidocaine salt increased significantly in microporated (270.57 ± 3.73 μg/cm2) skin as compared to intact skin (142.19 ± 13.70 μg/cm2) at 24 h. The receptor delivery of lidocaine base from microporated skin was significantly higher (312.37 ± 10.57 μg/cm2) than intact skin (169.68 ± 24.09 μg/cm2) up to 8 h. Lag time decreased significantly for the base (2.24 ± 0.17 h to 0.64 ± 0.05 h) and salt (4.76 ± 0.31 h to 1.47 ± 0.21 h) after microporation. Vacuum compression molding was demonstrated as a novel technique to fabricate uniform, solvent-free, strong polymer microneedles in a short time.

Simple method to measure rheological properties of soft surfaces by a micro-needle contact.

We developed a simple method to investigate rheological properties of soft surfaces, such as polymeric liquids and colloidal suspensions, by capturing the images of a metal micro-needle inserted into the surface. At contact, a meniscus-like deformation is formed on the surface. By relating the shape of the deformation to the balance of applied forces, local elasticity and viscosity just inside the surface are obtained. With a facile setup and rapid measurement process, the present method can be implemented to variety of systems, for instance, drying sessile drops and small volume of liquid confined in a capillary.

Binary ethosomes-based transdermal patches assisted by metal microneedles significantly improve the bioavailability of carvedilol

This study aimed to develop a strategy combining binary ethsomes (BES) and microneedles (MNs) to improve the bioavailability of drugs that are poorly bioavailable by oral administration, such as carvedilol (CL). The formula of BES was optimized by Box-Benhnken Designes from four aspects: particle size, zeta potential, encapsulation efficiency and cumulative release in vitro. The optimized BES was then mixed with polyvinylpyrrolidone and sprayed onto the silk fibroin matrix by electrospray to obtain transdermal drug delivery patches (TDDP). In vitro skin penetration test showed that, TDDP has much better transdermal drug release performance compared with free drugs, and MNs-assisted TDDP (MNs-TDDP) can deliver more drugs to the receiving chamber. In vivo studies indicate that MNs-TDDP can significantly reduce the fluctuation of CL concentration in plasma and increase serum level of NO, thereby lower blood pressure for a longer time. These results suggest that the bioavailability of CL can be greatly improved via administration of MNs-TDDP, compared with the oral route. Considering its advantages of non-invasiveness, convenience and good biosafety, MNs-TDDP has a promising prospect in improving the bioavailability of drugs for treating chronic diseases such as hypertension.

Determination of Transdermal Rate of Metallic Microneedle Array through an Impedance Measurements-Based Numerical Check Screening Algorithm.

Microneedle systems have been widely used in health monitoring, painless drug delivery, and medical cosmetology. Although many studies on microneedle materials, structures, and applications have been conducted, the applications of microneedles often suffered from issues of inconsistent penetration rates due to the complication of skin-microneedle interface. In this study, we demonstrated a methodology of determination of transdermal rate of metallic microneedle array through impedance measurements-based numerical check screening algorithm. Metallic sheet microneedle array sensors with different sizes were fabricated to evaluate different transdermal rates. In vitro sensing of hydrogen peroxide confirmed the effect of transdermal rate on the sensing outcomes. An FEM simulation model of a microneedle array revealed the monotonous relation between the transdermal state and test current. Accordingly, two methods were primely derived to calculate the transdermal rate from the test current. First, an exact logic method provided the number of unpenetrated tips per sheet, but it required more rigorous testing results. Second, a fuzzy logic method provided an approximate transdermal rate on adjacent areas, being more applicable and robust to errors. Real-time transdermal rate estimation may be essential for improving the performance of microneedle systems, and this study provides various fundaments toward that goal.

Probing the formation of anhydrovinblastine in Catharanthus roseus by single-cell mass spectrometry

Anhydrovinblastine, derived from the periwinkle plant Catharanthus roseus, is the direct precursor of vinblastine that is an important drug to treat a number of types of cancer. Insights into the formation mechanism of anhydrovinblastine at the cell level is beneficial for improving the industrial production of anticancer drugs. Herein, metal microneedle was modified for extracting single-cell metabolites of Catharanthus roseus, and then the microneedle was directly served as emitter of electrospray ionization for direct mass spectrometry analysis of single-cell metabolites. Sampling efficiency of microneedle with different surface modifications were compared. Different cells in stem, root, and leaf of Catharanthus roseus were also investigated. Our results showed that two key monomeric precursor molecules, vindoline and catharanthine, are from different cells in Catharanthus roseus and could mix to form anhydrovinblastine. This work shows a new method for probing the biosynthesis and formation of bioactive molecules in living systems.

Cleanroom and Template Free Fabrication of Single Polygonal Shaped Microneedle.

For painless skin penetration, microneedles require optimal geometry due to human skin's inherent elastic properties. The fabrication of desired shape microneedle is very critical. To our knowledge, the polygonal geometry microneedle has not been investigated before. To address this issue, in this communication, we propose a novel cleanroom free fabrication of single metal microneedle with square cross section. The microneedle was fabricated using sputtering technique without any mask or template. The morphological analysis with respect to various sputtering parameters via. Argon (Ar) pipe position, rotating speed, working pressure was discussed in detail. The microneedle geometry, its assisted pain was visualized using finite element analysis (FEM). The theoretical evaluations were subsequently compared with experimentally fabricated microneedle. This is the first step towards more rational design of polygonal microneedle geometry.

Electrospinning/electrospraying coatings for metal microneedles: A design of experiments (DOE) and quality by design (QbD) approach

The research presented here shows QbD implementation for the optimisation of the key process parameters in electrohydrodynamic atomisation (EHDA). Here, the electrosprayed nanoparticles and electrospun fibers consisting of a polymeric matrix and dye. Eight formulations were assessed consisting of 5% w/v of polycaprolactone (PCL) in dichloromethane (DCM) and 5% w/v polyvinylpyrrolidone (PVP) in ethanol. A full factorial DOE was used to assess the various parameters (applied voltage, deposition distance, flow rate). Further particle and fiber analysis using Scanning Electron Microscopy (SEM), Differential Scanning Calorimetry (DSC), Thermogravimetric Analysis (TGA), Fourier Transform Infrared Spectroscopy (FTIR), particle/fiber size distribution. In addition to this in vitro release studied were carried out using fluorescein and Rhodamine B as model dyes and in vitro permeation studies were applied. The results show a significant difference in the morphology of resultant structures as well as a more rapid release profile for the PVP particles and fibers in comparison to the sustained release profiles found with PCL. In vitro drug release studies showed 100% drug release after 7 days for PCL particles and showed 100% drug release within 120 min for PVP particles. The release kinetics and the permeation study showed that the MN successfully pierced the membrane and the electrospun MN coating released a large amount of the loaded drug within 6 h. This study has demonstrated the capability of these robust MNs to encapsulate a diverse range drugs within a polymeric matrix giving rise to the potential of developed personalised medical devices.

Ultradeformable Lipid Vesicles Localize Amphotericin B in the Dermis for the Treatment of Infectious Skin Diseases

Cutaneous fungal and parasitic diseases remain challenging to treat, as available therapies are unable to permeate the skin barrier. Thus, treatment options rely on systemic therapy, which fail to produce high local drug concentrations but can lead to significant systemic toxicity. Amphotericin B (AmB) is highly efficacious in the treatment of both fungal and parasitic diseases such as cutaneous leishmaniasis but is reserved for parenteral administration in patients with severe pathophysiology. Here, we have designed and optimized AmB-transfersomes [93.5% encapsulation efficiency, 150 nm size, and good colloidal stability (-35.02 mV)] that can remain physicochemically stable (>90% drug content) at room temperature and 4 °C over 6 months when lyophilized and stored under desiccated conditions. AmB-transfersomes possessed good permeability across mouse skin (4.91 ± 0.41 μg/cm2/h) and 10-fold higher permeability across synthetic Strat-M membranes. In vivo studies after a single topical application in mice showed permeability and accumulation within the dermis (>25 μg AmB/g skin 6 h postadministration), indicating the delivery of therapeutic amounts of AmB for mycoses and cutaneous leishmaniasis, while a single daily administration in Leishmania (Leishmania) amazonensis infected mice over 10 days, resulted in excellent efficacy (98% reduction in Leishmania parasites). Combining the application of AmB-transfersomes with metallic microneedles in vivo increased the levels in the SC and dermis but was unlikely to elicit transdermal levels. In conclusion, AmB-transfersomes are promising and stable topical nanomedicines that can be readily translated for parasitic and fungal infectious diseases.

Biomedical Applications of Polymeric Microneedles for Transdermal Therapeutic Delivery and Diagnosis: Current Status and Future Perspectives

AbstractTransdermal drug delivery is a crucial extension of drug administration routes and has been widely acknowledged as an alternative way to traditional oral administration and subcutaneous injections due to the advantages such as increased dosage efficacy, decreased systemic side effect, and improved patient compliance. The past few decades have witnessed biomedical applications of microneedles in various cutting‐edge fields. Microneedles are needles with micron‐scale length which can pierce the epidermis of the skin in a minimally invasive manner for transdermal drug delivery. Compared with inorganic and metal microneedles, polymeric microneedles have attracted more attention because of their superior biocompatibility, nontoxicity, and biodegradability. In this review, the state‐of‐art and future biomedical applications of polymeric microneedles are summarized. First of all, a brief introduction to the polymeric microneedles, including types of polymeric microneedles and methods for the fabrication is included. Then the biomedical applications of polymeric microneedles in transdermal drug delivery and diagnosis are summarized in detail. Finally, discussions on the current limitations and future perspectives of polymeric microneedles are provided.