Application of Microneedle Arrays for Enhancement of Transdermal Permeation of Insulin: In Vitro Experiments, Scaling Analyses and Numerical Simulations

Microfluidic-based systems for the management of diabetes

Diabetes currently affects approximately 500 million people worldwide and is one of the most common causes of mortality in the United States. To diagnose and monitor diabetes, finger-prick blood glucose testing has long been used as the clinical gold standard. For diabetes treatment, insulin is typically delivered subcutaneously through cannula-based syringes, pens, or pumps in almost all type 1 diabetic (T1D) patients and some type 2 diabetic (T2D) patients. These painful, invasive approaches can cause non-adherence to glucose testing and insulin therapy. To address these problems, researchers have developed miniaturized blood glucose testing devices as well as microfluidic platforms for non-invasive glucose testing through other body fluids. In addition, glycated hemoglobin (HbA1c), insulin levels, and cellular biomechanics-related metrics have also been considered for microfluidic-based diabetes diagnosis. For the treatment of diabetes, insulin has been delivered transdermally through microdevices, mostly through microneedle array-based, minimally invasive injections. Researchers have also developed microfluidic platforms for oral, intraperitoneal, and inhalation-based delivery of insulin. For T2D patients, metformin, glucagon-like peptide 1 (GLP-1), and GLP-1 receptor agonists have also been delivered using microfluidic technologies. Thus far, clinical studies have been widely performed on microfluidic-based diabetes monitoring, especially glucose sensing, yet technologies for the delivery of insulin and other drugs to diabetic patients with microfluidics are still mostly in the preclinical stage. This article provides a concise review of the role of microfluidic devices in the diagnosis and monitoring of diabetes, as well as the delivery of pharmaceuticals to treat diabetes using microfluidic technologies in the recent literature.

Transdermal drug delivery systems for the effective management of type 2 diabetes mellitus: A review

Type 2 Diabetes mellitus (T2DM) is characterized by either insufficient insulin production or the inability to take it up for the glycemic regulation in the human body. According to WHO reports, T2DM will be the seventh-largest syndrome resulting in mortality by 2030. To tackle this chronic metabolic disorder, the person with diabetes population depends on subcutaneous administration (Sub-Q) of insulin and certain oral hypoglycemic drugs. However, these current invasive practices suffered from painful injections, needle phobia, multiple doses, risk of infection and poor-patient compliance. Hence, the search for a non-invasive and patient-friendly insulin administration system was high in the past decades leading to the development of Transdermal Drug Delivery Systems (TDDS). These can offer rapid and sustained release of therapeutic compounds at controlled rates with no pain during the administration. In recent years, the usage of such TDDS has been increasing at an exponential rate in Type 2 diabetes management. In the present review, the scholarly works on the different modes of TDDS were comprehensively reported chronlogically to appreciate their developments. Conclusively, this review critically identified prevailing research gaps in the current TDDS research and presented potential research hotspots for the prospect development in T2DM management.

Bioimaging of Dissolvable Microneedle Arrays: Challenges and Opportunities

The emergence of microneedle arrays (MNAs) as a novel, simple, and minimally invasive administration approach largely addresses the challenges of traditional drug delivery. In particular, the dissolvable MNAs act as a promising, multifarious, and well-controlled platform for micro-nanotransport in medical research and cosmetic formulation applications. The effective delivery mostly depends on the behavior of the MNAs penetrated into the body, and accurate assessment is urgently needed. Advanced imaging technologies offer high sensitivity and resolution visualization of cross-scale, multidimensional, and multiparameter information, which can be used as an important aid for the evaluation and development of new MNAs. The combination of MNA technology and imaging can generate considerable new knowledge in a cost-effective manner with regards to the pharmacokinetics and bioavailability of active substances for the treatment of various diseases. In addition, noninvasive imaging techniques allow rapid, receptive assessment of transdermal penetration and drug deposition in various tissues, which could greatly facilitate the translation of experimental MNAs into clinical application. Relying on the recent promising development of bioimaging, this review is aimed at summarizing the current status, challenges, and future perspective on in vivo assessment of MNA drug delivery by various imaging technologies.

Microneedle-mediated transdermal delivery of naloxone hydrochloride for treatment of opioid overdose

Naloxone (NAL) is administered parenterally or intranasally for treating opioid overdose. The short duration of action of NAL calls for frequent re-dosing which may be eliminated by the development of a transdermal system. This study aimed to assess the effect of microneedles on improving the skin permeation of NAL hydrochloride. In vitro permeation of NAL across intact and microneedle-treated (Dr. Pen™ Ultima A6) porcine skin was evaluated. The effect of microneedle length and application duration, and donor concentration on NAL permeation were investigated. In-vitro in-vivo correlation of the permeation results was done to predict the plasma concentration kinetics of NAL in patients. In vitro passive permeation of NAL after 6 h was observed to be 8.25±1.06 µg/cm². A 56- and 37-fold enhancement was observed with 500 and 250 µm needles applied for 1 min, respectively. Application of 500 µm MNs for 2 min significantly reduced the lag time to ~ 8 min and increasing the donor concentration for the same treatment group doubled the permeation (p < 0.05). Modeling simulations demonstrated the attainment of pharmacokinetic profile of NAL comparable to those obtained with the FDA-approved intramuscular and intranasal devices. Microneedle-mediated transdermal delivery holds potential for rapid and sustained NAL delivery for opioid overdose treatment.

Microneedle-Mediated Delivery of Lipid-Coated Cisplatin Nanoparticles for Efficient and Safe Cancer Therapy

Cisplatin is the first-line chemotherapeutic agent, but its systemic toxicity and side effects severely limit its clinical use. We report a microneedle technique to mediate the transdermal delivery of lipid-coated cisplatin nanoparticles (LCC-NPs) for efficient and safe cancer therapy. Cisplatin was encapsulated by tumor-targeting pH-responsive lipid nanoparticles with a high loading rate of 80%, and the encapsulation substantially increased the solubility of cisplatin and enhanced its antitumor efficiency in vitro. The LCC-NPs were embedded in dissolvable microneedles, and released from the microneedles after inserting into the skin. This enabled the nanoparticles to pass the stratum corneum for safe local delivery. An in vivo study with a xenograft tumor animal model demonstrated that microneedle arrays loaded with cisplatin nanoparticles significantly increased cytotoxicity and apoptosis in cancer cells with an apoptotic index of 58.6%, resulting in significantly reduced tumor volume and weight. Moreover, serum platinum, pulmonary toxicity, hepatotoxicity, and nephrotoxicity were not detected in vivo, indicating that this technique is biosafe. The cisplatin-nanoparticle microneedle system developed in this study may offer promising opportunities in cancer therapy for enhancing antitumor effects and reducing systemic toxicity and side effects.

Formulation, physicochemical characterization and in vitro evaluation of human insulin-loaded microspheres as potential oral carrier

Abstract

The objective of the present investigation was to formulate and characterize the human insulin entrapped Eudragit S100 microspheres containing protease inhibitors and to develop an optimized formulation with desirable features. A w/o/w multiple emulsion solvent evaporation technique was employed to produce microspheres of human insulin using Eudragit S-100 as coating material and polyvinyl alcohol as a stabilizer. The resultant microspheres were evaluated for drug-excipient compatibility, encapsulation efficiency, particle size, surface morphology, micromeritic properties, enteric nature, and in vitro drug release studies. Micromeritic properties indicated good flow properties and compressibility. In present investigation formulation F6 with drug/polymer ratio (1:100) was found to be optimal in terms of evaluated parameters where it showed a significantly higher percentage of encapsulation efficiency (76.84%) with minimal drug release (3.25%) in an acidic environment. The optimized formulation (F6) also possessed good spherical shape and particle size (57.42 µm) required to achieve the desired in vitro drug release profile at pH 7.4. The results confirmed that human insulin-loaded Eudragit S-100 microspheres containing protease inhibitor possessed good encapsulation efficiency, pH dependant controlled release carrying encapsulated insulin to its optimum site of absorption. This ultimately resulted in enhanced insulin absorption and biological response.

Graphical Abstract

Microneedle-assisted transdermal delivery of Zolmitriptan: effect of microneedle geometry, in vitro permeation experiments, scaling analyses and numerical simulations

OBJECTIVE

The present study was aimed to investigate the effect of salient microneedle (MN) geometry parameters like length, density, shape and type on transdermal permeation enhancement of Zolmitriptan (ZMT).

METHODS

Two types of MN devices viz. AdminPatch^® arrays (ADM) (0.6, 0.9, 1.2 and 1.5 mm lengths) and laboratory fabricated polymeric MNs (PM) of 0.6 mm length were employed. In the case of PMs, arrays were applied thrice at different places within a 1.77 cm² skin area (PM-3) to maintain the MN density closer to 0.6 mm ADM. Scaling analyses was done using dimensionless parameters like concentration of ZMT (C_t/C_s), thickness (h/L) and surface area of the skin (Sa/L²).

RESULTS

Micro-injection molding technique was employed to fabricate PM. Histological studies revealed that the PM, owing to their geometry/design, formed wider and deeper microconduits when compared to ADM of similar length. Approximately 3.17- and 3.65-fold increase in ZMT flux values were observed with 1.5 mm ADM and PM-3 applications when compared to the passive studies. Good correlations were observed between different dimensionless parameters with scaling analyses. Numerical simulations, using MATLAB and COMSOL software, based on experimental data and histological images provided information regarding the ZMT skin distribution after MN application.

DISCUSSION

Both from experimental studies and simulations, it was inferred that PM were more effective in enhancing the transdermal delivery of ZMT when compared to ADM.

CONCLUSIONS

The study suggests that MN application enhances the ZMT transdermal permeation and the geometrical parameters of MNs play an important role in the degree of such enhancement.

Effect of microneedles on transdermal permeation enhancement of amlodipine

The present study aimed to investigate the effect of microneedle (MN) geometry parameters like length, density, shape and type on transdermal permeation enhancement of amlodipine (AMLO). Two types of MN devices viz. AdminPatch® arrays (ADM) (0.6, 1.2 and 1.5 mm lengths) and laboratory-fabricated polymeric MNs (PM) of 0.6 mm length were employed. In the case of PMs, arrays were applied thrice at different places within a 1.77-cm² skin area (PM-3) to maintain the MN density closer to 0.6 mm ADM. Scaling analyses were done using dimensionless parameters like concentration of AMLO (C_t/C_s), thickness (h/L) and surface area of the skin (Sa/L²). Microinjection moulding technique was employed to fabricate PM. Histological studies revealed that the PM, owing to their geometry/design, formed wider and deeper microconduits when compared to ADM of similar length. Approximately 6.84- and 6.11-fold increase in the cumulative amount (48 h) of AMLO permeated was observed with 1.5 mm ADM and PM-3 treatments respectively, when compared to passive permeation amounts. Good correlations (R ² > 0.89) were observed between different dimensionless parameters with scaling analyses. The enhancement in AMLO permeation was found to be in the order of 1.5 mm ADM ≥ PM-3 > 1.2 mm ADM > 0.6 mm ADM ≥PM-1 > passive. The study suggests that MN application enhances the AMLO transdermal permeation and the geometrical parameters of MNs play an important role in the degree of such enhancement.