A systematic review of carbohydrate-based microneedles: current status and future prospects

Claes K, Blondeel P, Monstrey S, Dorpe JV, Van Vlierberghe S. Photo-crosslinkable polyester microneedles as sustained drug release systems toward hypertrophic scar treatment

Burn injuries can result in a significant inflammatory response, often leading to hypertrophic scarring (HTS). Local drug therapies e.g. corticoid injections are advised to treat HTS, although they are invasive, operator-dependent, extremely painful and do not permit extended drug release. Polymer-based microneedle (MN) arrays can offer a viable alternative to standard care, while allowing for direct, painless dermal drug delivery with tailorable drug release profile. In the current study, we synthesized photo-crosslinkable, acrylate-endcapped urethane-based poly(ε-caprolactone) (AUP-PCL) toward the fabrication of MNs. Physico-chemical characterization (1H-NMR, evaluation of swelling, gel fraction) of the developed polymer was performed and confirmed successful acrylation of PCL-diol. Subsequently, AUP-PCL, and commercially available PCL-based microneedle arrays were fabricated for comparative evaluation of the constructs. Hydrocortisone was chosen as model drug. To enhance the drug release efficiency of the MNs, Brij®35, a nonionic surfactant was exploited. The thermal properties of the MNs were evaluated via differential scanning calorimetry. Compression testing of the arrays confirmed that the MNs stay intact upon applying a load of 7 N, which correlates to the standard dermal insertion force of MNs. The drug release profile of the arrays was evaluated, suggesting that the developed PCL arrays can offer efficient drug delivery for up to two days, while the AUP-PCL arrays can provide a release up to three weeks. Finally, the insertion of MN arrays into skin samples was performed, followed by histological analysis demonstrating the AUP-PCL MNs outperforming the PCL arrays upon providing pyramidical-shaped perforations through the epidermal layer of the skin.

Bioengineered carbohydrate polymers for colon-specific drug release: Current trends and future prospects

The worldwide health burden of colorectal cancer is still substantial, and traditional chemotherapeutic drugs sometimes have poor selectivity, which can result in systemic toxicity and unfavorable side effects. For colon-specific medication delivery, bioengineered carbohydrate polymers have shown promise as carriers. They may enhance treatment effectiveness while minimizing systemic exposure and associated side effects. The unique properties of these manufactured or naturally occurring biopolymers, such as hyaluronic acid, chitosan, alginate, and pectin, enable targeted medicine release. These qualities can be changed to meet the physiological needs of the colon. In the context of colorectal cancer therapy, this article provides a comprehensive overview of current developments and prospective future directions in the field of bioengineered carbohydrate polymer synthesis for colon-specific drug delivery. We discuss numerous techniques for achieving colon-targeted drug release, including enzyme-sensitive polymers, pH-responsive devices, and microbiota-activated processes. To increase tumor selectivity and cellular uptake, we also examine the inclusion of active targeting approaches, such as conjugating specific ligands. Furthermore, we discuss the potential of combination treatment strategies, which use the coadministration of numerous therapeutic medications to target multiple pathways implicated in cancer growth and address drug resistance mechanisms. We address recent biomimetic advances that potentially improve the biocompatibility, cellular uptake, and tumor penetration of carbohydrate polymer-based nanocarriers. These methods involve protein corona engineering and cell membrane coating. Furthermore, we look at the possibility of intelligent and sensitive systems that may adjust their behaviors in response to certain inputs or feedback loops, allowing for precise and regulated drug distribution.

Advances in Polysaccharide-Based Microneedle Systems for the Treatment of Ocular Diseases

The eye, a complex organ isolated from the systemic circulation, presents significant drug delivery challenges owing to its protective mechanisms, such as the blood-retinal barrier and corneal impermeability. Conventional drug administration methods often fail to sustain therapeutic levels and may compromise patient safety and compliance. Polysaccharide-based microneedles (PSMNs) have emerged as a transformative solution for ophthalmic drug delivery. However, a comprehensive review of PSMNs in ophthalmology has not been published to date. In this review, we critically examine the synergy between polysaccharide chemistry and microneedle technology for enhancing ocular drug delivery. We provide a thorough analysis of PSMNs, summarizing the design principles, fabrication processes, and challenges addressed during fabrication, including improving patient comfort and compliance. We also describe recent advances and the performance of various PSMNs in both research and clinical scenarios. Finally, we review the current regulatory frameworks and market barriers that are relevant to the clinical and commercial advancement of PSMNs and provide a final perspective on this research area.

Microneedles Based on a Biodegradable Polymer-Hyaluronic Acid

Transdermal transport can be challenging due to the difficulty in diffusing active substances through the outermost layer of the epidermis, as the primary function of the skin is to protect against the entry of exogenous compounds into the body. In addition, penetration of the epidermis for substances hydrophilic in nature and particles larger than 500 Da is highly limited due to the physiological properties and non-polar nature of its outermost layer, namely the stratum corneum. A solution to this problem can be the use of microneedles, which "bypass" the problematic epidermal layer by dispensing the active substance directly into the deeper layers of the skin. Microneedles can be obtained with various materials and come in different types. Of special interest are carriers based on biodegradable and biocompatible polymers, such as polysaccharides. Therefore, this paper reviews the latest literature on methods to obtain hyaluronic acid-based microneedles. It focuses on the current advancements in this field and consequently provides an opportunity to guide future research in this area.

Protein-based microneedles for biomedical applications: A systematic review

Microneedles are minimally-invasive devices with the unique capability of bypassing physiological barriers. Hence, they are widely used for different applications from drug/vaccine delivery to diagnosis and cosmetic fields. Recently, natural biopolymers (particularly carbohydrates and proteins) have garnered attention as safe and biocompatible materials with tailorable features for microneedle construction. Several review articles have dealt with carbohydrate-based microneedles. This review aims to highlight the less-noticed role of proteins through a systematic search strategy based on the PRISMA guideline from international databases of PubMed, Science Direct, Scopus, and Google Scholar. Original English articles with the keyword "microneedle(s)" in their titles along with at least one of the keywords "biopolymers, silk, gelatin, collagen, zein, keratin, fish-scale, mussel, and suckerin" were collected and those in which the proteins undertook a structural role were screened. Then, we focused on the structures and applications of protein-based microneedles. Also, the unique features of some protein biopolymers that make them ideal for microneedle construction (e.g., excellent mechanical strength, self-adhesion, and self-assembly), as well as the challenges associated with them were reviewed. Altogether, the proteins identified so far seem not only promising for the fabrication of "better" microneedles in the future but also inspiring for designing biomimetic structural biopolymers with ideal characteristics.

Performance Enhancement of PLA-Based Blend Microneedle Arrays through Shish-Kebab Structuring Strategy in Microinjection Molding

Poly(lactic acid) (PLA) microneedles have been explored extensively, but the current regular fabrication strategy, such as thermoforming, is inefficient and poorly conformable. In addition, PLA needs to be modified as the application of microneedle arrays made of pure PLA is limited because of their easy tip fracture and poor skin adhesion. For this purpose, in this article, we reported a facile and scalable strategy to fabricate the microneedle arrays of the blend of PLA matrix and poly(p-dioxanone) (PPDO) dispersed phase with complementary mechanical properties through microinjection molding technology. The results showed that the PPDO dispersed phase could be in situ fibrillated under the effect of the strong shear stress field generated in micro-injection molding. These in situ fibrillated PPDO dispersed phases could hence induce the formation of the shish-kebab structures in the PLA matrix. Particularly for PLA/PPDO (90/10) blend, there are the densest and most perfect shish-kebab structures formed. The above microscopic structure evolution could be also advantageous to the enhancement in the mechanical properties of microparts of PLA/PPDO blend (tensile microparts and microneedle arrays), e.g., the elongation at break of the blend is almost double that of pure PLA while still maintaining the high stiffness (Young's modulus of 2.7 GPa) and the high strength (tensile strength of 68.3 MPa) in the tensile test, and relative to pure PLA, there is 100% or more increase in the load and displacement of microneedle in the compression test. This could open up new spaces for expanding the industrial application of the fabricated microneedle arrays.

Microneedles for Efficient and Precise Drug Delivery in Cancer Therapy

Cancer is the leading cause of death, acting as a global burden, severely impacting the patients’ quality of life and affecting the world economy despite the expansion of cumulative advances in oncology. The current conventional therapies for cancer which involve long treatment duration and systemic exposure of drugs leads to premature degradation of drugs, a massive amount of pain, side effects, as well as the recurrence of the condition. There is also an urgent demand for personalized and precision-based medicine, especially after the recent pandemic, to avoid future delays in diagnosis or treatments for cancer patients as they are very essential in reducing the global mortality rate. Recently, microneedles which consist of a patch with tiny, micron-sized needles attached to it have been quite a sensation as an emerging technology for transdermal application to diagnose or treat various illnesses. The application of microneedles in cancer therapies is also being extensively studied as they offer a myriad of benefits, especially since microneedle patches offer a better treatment approach through self administration, painless treatment, and being an economically and environmentally friendly approach in comparison with other conventional methods. The painless gains from microneedles significantly improves the survival rate of cancer patients. The emergence of versatile and innovative transdermal drug delivery systems presents a prime breakthrough opportunity for safer and more effective therapies, which could meet the demands of cancer diagnosis and treatment through different application scenarios. This review highlights the types of microneedles, fabrication methods and materials, along with the recent advances and opportunities. In addition, this review also addresses the challenges and limitations of microneedles in cancer therapy with solutions through current studies and future works to facilitate the clinical translation of microneedles in cancer therapies.

Topical Delivery of ROS-Responsive Methotrexate Prodrug Nanoassemblies by a Dissolvable Microneedle Patch for Psoriasis Therapy

Purpose

Oxidative stress, nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) and adenosine signaling are factors associated with psoriatic inflammation. Topical delivery of methotrexate (MTX) has become an option to overcome the side effects caused by systemic therapy in psoriasis, leading to the suppression of NF-κB activation through boosting adenosine release. However, thickened psoriatic skin is the primary restriction against local drug delivery.

Methods

In this study, a ROS responsive MTX prodrug (MTX-TK-HA) was synthesized with the feature of CD44 mediated active targeting to hyperproliferative keratinocytes. MTX prodrug and PLA-mPEG were formulated by nano-precipitation method to develop the MTX-TK-HA/PLA-mPEG nanoassemblies. To achieve painless transdermal delivery, a dissolving microneedle was applied for direct loading of these nanoassemblies by micromolding technique. The particle size, zeta potential, ROS-responsiveness, permeability, and mechanical strength of nanoassemblies and microneedle arrays were determined, respectively. Then, MTT assay, immunoblot analysis, ELISA assay, flow cytometry, and histological staining were utilized to thoroughly evaluate the efficacy of nanoassemblies-loaded microneedles in an imiquimod-induced psoriatic mouse model.

Results

Nanoassemblies-loaded microneedle arrays were capable of significantly penetrating imiquimod-induced psoriatic epidermis in mice. The efficient topical delivery of these nanoassemblies was achieved by potent mechanical strength and hyaluronic acid as the dissolvable matrix for microneedle arrays. CD44-mediated endocytosis enabled the intracellular uptake of nanoassemblies in keratinocytes, and methotrexate was released from MTX-TK-HA with ROS stimuli, followed by suppressing the proliferation of epidermal cells via NF-κB pathway blockade.

Conclusion

In a psoriatic mouse model, nanoassemblies loaded microneedle arrays relieve inflammatory skin disorders via regulation of adenosine and NF-κB signaling. Our study offered a rational design for the transdermal delivery of hydrophobic agents and defined an effective therapeutic option for psoriasis treatment.

Dissolving microneedles for effective and painless intradermal drug delivery in various skin conditions: A systematic review

Intra- and transdermal administration of substances via percutaneous injection is effective but considered painful, and inconvenient in addition to bringing forth biohazardous waste material. In contrast to injection, topical drug application, which includes ointments, creams and lotions, increases the local drug load. Moreover, it has reduced side effects compared to systemic administration. However, the epidermis poses a barrier to high molecular weight substances, limiting the delivery efficiency. Dissolving microneedles (DMN) are hydrophilic, mostly polymer-based constructs that are capable of skin penetration and were developed to provide painless and direct dermal drug delivery. This systematic review provides a comprehensive overview of the available clinical evidence for the use of DMN to treat various skin conditions. According to the PRISMA statement, a systematic search for articles on the use of DMN for dermatological indications was conducted on three different databases (Pubmed, Embase, and the Cochrane library). Only human clinical trials were considered. Qualitative assessment was done by two separate reviewers using the Cochrane risk of bias (RoB 2) and Chambers' criteria assessment tools. The search yielded 1090 articles. After deduplication and removal of ineligible records, 889 records were screened on title and abstract. Full text screening was done for 18 articles and ultimately 17 articles were included of which 15 were randomized controlled trials and two were case series. The quality assessment showed that the majority of included studies had low to no risk of bias. Clinical data supports that DMN are an excellent, effective, and pain free drug delivery method for multiple dermatological disorders including skin aging, hyperpigmentation, psoriasis, warts, and keloids by supplying a painless and effective vehicle for intradermal/intralesional drug administration. Microneedle technology provides a promising non- to minimally-invasive alternative to percutaneous injection.

Treatment of Hypertrophic Scars with Corticoid-Embedded Dissolving Microneedles

Hypertrophic scarring (HTS) is frequently observed after deep dermal and full-thickness skin defects. Local drug delivery in HTS has been shown more effective compared to other (minimally) invasive treatments. Disadvantages being operator-dependency and non-uniform drug distribution. Moreover, injections are painful and difficult when confronted with extensive scars or HTS in children. Corticoid-embedded dissolving microneedles (CEDMN) were developed that provide painless skin penetration and direct dermal drug delivery. Hyaluronic acid-based DMN and CEDMN patches were utilized. Structural analysis was performed via nuclear magnetic resonance (NMR) spectroscopy while gel permeation chromatography (GPC) was applied to determine chain length (molar mass) and dispersity of hyaluronic acid. Mechanical properties were evaluated by compression testing. Five burn victims with HTS were included. For each individual, three comparable scars were chosen. One control scar was left untreated. Two scars were treated with either 600 or 800 µm CEDMN patches. Patients were treated monthly for 4 months. Treatment with 800 µm CEDMN was initiated after 8 weeks. Assessor-blinded POSAS was registered. Hydration, evaporation, color and elasticity were recorded. The physico-chemical characterization suggests that the mechanical properties enable skin penetration and adequate drug delivery. Patients experienced the therapy as painless. According to the POSAS, all scars improved over time. However, the scars that were treated with CEDMN patches improved faster and with increased increment. The 800 µm CEDMN ensured the fastest POSAS-decrease. Hyaluronic acid-based CEDMN patches are valuable alternatives to intracicatrical injections, as they offer a painless and effective method for administering corticosteroids in HTS.

Thermostability and in vivo performance of AAV9 in a film matrix

BACKGROUND

Adeno-associated virus (AAV) vectors are stored and shipped frozen which poses logistic and economic barriers for global access to these therapeutics. To address this issue, we developed a method to stabilize AAV serotype 9 (AAV9) in a film matrix that can be stored at ambient temperature and administered by systemic injection.

METHODS

AAV9 expressing the luciferase transgene was mixed with formulations, poured into molds and films dried under aseptic conditions. Films were packaged in individual particle-free bags with foil overlays and stored at various temperatures under controlled humidity. Recovery of AAV9 from films was determined by serial dilution of rehydrated film in media and infection of HeLa RC32 cells. Luciferase expression was compared to that of films rehydrated immediately after drying. Biodistribution of vector was determined by in vivo imaging and quantitative real-time PCR. Residual moisture in films was determined by Karl Fischer titration.

RESULTS

AAV9 embedded within a film matrix and stored at 4 °C for 5 months retained 100% of initial titer. High and low viscosity formulations maintained 90 and 85% of initial titer after 6 months at 25 °C respectively. AAV was not detected after 4 months in a Standard Control Formulation under the same conditions. Biodistribution and transgene expression of AAV stored in film at 25 or 4 °C were as robust as vector stored at -80 °C in a Standard Control Formulation.

CONCLUSIONS

These results suggest that storage of AAV in a film matrix facilitates easy transport of vector to remote sites without compromising in vivo performance.

Sugar-Triggered Burst Drug Releasing Poly-Lactic Acid (PLA) Microneedles and Its Fabrication Based on Solvent-Casting Approach

Microneedles have emerged as a novel transdermal delivery tool that enables the delivery of various products such as drugs, vaccines, or cosmetic ingredients. Although the demand for solid microneedles composed of biocompatible polymer is increasing, the manufacture of microneedles using poly-lactic acid (PLA) with rapid drug-releasing is yet to be established and the process is still in its infancy. Here, we propose a novel strategy for the fabrication of PLA solid microneedles which enable a drug to be burst-released based on a solvent-casting process. This approach offers extreme simplicity, broad geometric capability, cost-effectiveness, and scalability based on high fidelity-replicas. It was verified that microneedles of various heights (250–500 μm) could be fabricated with appropriate mechanical strength to penetrate the stratum corneum layer of skin. By adding sugar in the composition of PLA microneedle, it was observed that both hydrophilic and hydrophobic drugs can be rapidly released within 30 min. Our burst drug-releasing PLA microneedle having both characteristics of solid microneedle and soluble microneedle and its fabrication approach based on solvent-casting will contribute to getting microneedle technology close to commercialization and beyond existing technical limitations.

Microneedle-Based Glucose Sensor Platform: From Vitro to Wearable Point-of-Care Testing Systems

Significant advanced have recently been made in exploiting microneedle-based (MN-based) diabetes devices for minimally invasive wearable biosensors and for continuous glucose monitoring. Within this emerging class of skin-worn MN-based sensors, the ISF can be utilized as a rich biomarker source to diagnose diabetes. While initial work of MN devices focused on ISF extraction, the recent research trend has been oriented toward developing in vivo glucose sensors coupled with optical or electrochemical (EC) instrumentation. This outlook highlights the essential characteristics of the sensing mechanisms, rational design, sensing properties, and applications. Finally, we describe the opinions about the challenge and prospects of optical and EC MN-based device platforms for the fabrication of wearable biosensors and their application potential in the future.

Research progress of microneedles in the treatment of melanoma

Melanoma is an aggressive malignancy deriving from melanocytes, which is characterized by high tendency of metastases and mortality rate. Current therapies for melanoma, like chemotherapy, immunotherapy and targeted therapy, have the problem of systemic exposure of drugs, which will lead to many side effects and premature degradation of drugs. The resulting low drug accumulation at the lesion limits the therapeutic effect on melanoma and makes the cure rate low. As an emerging drug delivery system, microneedles (MNs) can efficiently deliver drugs through the skin, increase the drug distribution in deeper tumor sites and minimize the leakage of therapeutic drugs into adjacent tissues, thus improving the therapeutic effect. In addition, compared with traditional drug delivery methods, MN-based drug delivery system has the advantages of simplicity, safety and little pain. So MNs can be developed for the treatment of melanoma, which can relieve the pain of patients and improve the survival rate. This review aims to introduce an update on the progress of MNs as an innovative strategy for melanoma, especially when MNs combining with different therapies against melanoma, such as chemotherapy, targeted therapy, immunotherapy, photothermal therapy (PTT), photodynamic therapy (PDT) and synergic therapy.

Microneedle-Based Natural Polysaccharide for Drug Delivery Systems (DDS): Progress and Challenges

In this focused progress review, the most widely accepted methods of transdermal drug delivery are hypodermic needles, transdermal patches and topical creams. However, microneedles (MNs) (or microneedle arrays) are low-invasive 3D biomedical constructs that bypass the skin barrier and produce systemic and localized pharmacological effects. In the past, biomaterials such as carbohydrates, due to their physicochemical properties, have been extensively used to manufacture microneedles (MNs). Due to their wide range of functional groups, carbohydrates enable the design and development of tunable properties and functionalities. In recent years, numerous microneedle products have emerged on the market, although much research needs to be undertaken to overcome the various challenges before the successful introduction of microneedles into the market. As a result, carbohydrate-based microarrays have a high potential to achieve a future step in sensing, drug delivery, and biologics restitution. In this review, a comprehensive overview of carbohydrates such as hyaluronic acid, chitin, chitosan, chondroitin sulfate, cellulose and starch is discussed systematically. It also discusses the various drug delivery strategies and mechanical properties of biomaterial-based MNs, the progress made so far in the clinical translation of carbohydrate-based MNs, and the promotional opportunities for their commercialization. In conclusion, the article summarizes the future perspectives of carbohydrate-based MNs, which are considered as the new class of topical drug delivery systems.