Glucose-Responsive Composite Microneedle Patch for Hypoglycemia-Triggered Delivery of Native Glucagon

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.

Biodegradable Microneedle Patch Confers Crocin with Outstanding Effects in the Treatment of Myocardial Infarction

Crocin (CRO), the main active component of Crocus sativus (saffron), exhibits significant therapeutic potential for the treatment of myocardial infarction (MI). However, its clinical application is hindered by poor oral administration due to the intestinal barrier. To overcome this limitation, a CRO-incorporated biodegradable microneedle (CRO-DMN) patch was developed to transdermally deliver CRO into the bloodstream, enhancing its therapeutic effect against MI. The microneedle patch, fabricated from sodium hyaluronate (HA), demonstrated excellent mechanical strength, effectively penetrating the stratum corneum and facilitating CRO infiltration to a depth exceeding 300 μm successfully. Studies revealed that CRO was fully released within 30 min postapplication, and the skin self-healed within 90 min after patch removal. Importantly, administration of CRO-DMNs to MI mice resulted in significant improvements in cardiac function and reductions in infarct size compared with CRO treatment alone. Additionally, CRO-DMNs also provided superior protective effects on the myocardium and mitochondria and significantly increased angiogenesis in the infarction border area. In conclusion, CRO-DMNs represent a promising transdermal drug delivery system that effectively improves the therapeutic efficacy of CRO in the treatment of MI.

Catechol-based chemistry for hypoglycemia-responsive delivery of zinc-glucagon via hydrogel-based microneedle patch technology

Hypoglycemia is a serious and potentially life-threatening condition for people with insulin-dependent diabetes. To provide a safeguard against hypoglycemia, we introduce a "smart" microneedle (MN) patch that senses glucose levels and delivers a blood glucose-raising agent (Zinc-Glucagon (Z-GCN)) in response to hypoglycemia. Herein, we describe the use of catechol and boronic acid chemistry to design a self-crosslinkable hydrogel-based MN that stimulates the release of Z-GCN during hypoglycemia. In this design, the catechol groups bind to Z-GCN through metal-ligand complexation. At hyperglycemia, boronic acids react with glucose to generate cyclic boronate esters. As the glucose concentration decreases, the boronic acid groups dissociate and are favored over Z-GCN in binding with catechol, which promotes the release of Z-GCN. We fully characterize the fabricated MN in vitro. Moreover, we further evaluate the MN and demonstrate the in vivo glucose-responsive delivery of Z-GCN from the patch. We also show its effectiveness in preventing hypoglycemia for up to 6 h in type 1 diabetic male rats against two consecutive insulin overdose challenges. Since many proteins/peptides have a high binding affinity to metal ions, the introduced mechanism driven by the competitive binding of catechol-metal ions has great implications in drug delivery applications of various protein/peptide-based therapeutics.

Collagen- and Hyaluronic Acid-Based Microneedles With Thiolated Pectin for Redox-Responsive Drug Delivery

Microneedles have emerged as an effective strategy to bypass the stratum corneum by creating microchannels in the skin, allowing for enhanced drug permeation with minimal invasiveness. Pectin, a natural polysaccharide, when modified with thiol (-SH) groups, exhibits redox-sensitive behavior, making it responsive to reducing agents such as glutathione and dithiothreitol (DTT). The objective of this study was to investigate the transdermal delivery efficacy of redox-responsive microneedle-containing thiolated pectin. Various molar ratios of thiolated pectin were synthesized through the ring-opening reaction followed by nucleophilic substitution of propylene sulfide with pectin. MN matrices were formulated with thiolated pectin at various molar ratios, hyaluronic acid, collagen, and trehalose. The stiffness and mechanical strength of the microneedles increased with higher thiol-containing pectin molecules. The in vitro skin permeation release showed a large amount of FITC release when no thiol group was conjugated to pectin. MN-thio: pectin (20:10) with H2O2 showed greater release at higher DTT concentrations, and in the absence of DTT, the release was 50 times less than without thiol. In summary, the redox-responsive microneedle containing thiolated pectin may be a promising vehicle for transdermal drug delivery by harvesting the reducing agents in the human body.

Glucose-Activated Programmed Hydrogel with Self-Switchable Enzyme-Like Activity for Infected Diabetic Wound Self-Adaptive Treatment

The defective blood glucose regulation ability of diabetic patients leading to bacterial infection, cellular oxidative stress, and vascular damage results in delayed healing of chronic diabetic wounds. Here, a glucose-activated self-switching enzyme-like activity programmed hydrogel is proposed to provide self-regulated timely intelligent insulin release affected by blood glucose fluctuations, thereby forming feedback blood glucose management and exerting a full-stage wound healing. The hydrogel is composed of Au─MoS2─phenylboronic acid nanozyme and insulin-loaded nitroimidazole-modified sodium alginate hypoxia-sensitive microcapsules and penylboronic-acid-modified chitosan. It utilizes glucose as a sacrificial agent to generate antibacterial reactive oxygen species by recognizing the hyperglycemia environment, and releasing insulin for blood glucose regulation for up to 12 h with the help of the enzyme-like catalysis-generated hypoxia environment. In a normoglycemia environment, the hydrogel switches the enzyme-like activity to supply oxygen, inhibiting further insulin release. The hydrogel achieves ≈3 times the wound recovery rate of commercial dressings through blood glucose regulation and improved wound microenvironment. The hydrogel has been proven to significantly improve the healing of chronic diabetic wounds by regulating the body's blood glucose homeostasis and implementing a staged healing treatment plan, providing a powerful solution for diabetic wound care.

Iontophoresis-driven transdermal drug delivery system based on porous microneedles for hyperuricemia treatment

An iontophoresis-driven porous microneedles (IPMNs) system has been developed for hyperuricemia management, which can be effectively prolong the anti-hyperuricemia effect. Porous microneedles (PMNs) with good biocompatibility, high porous volume, and excellent substance exchange capacity were firstly prepared for drug transdermal delivery and active iontophoresis.In vitro experiments showed that the transdermal delivery efficiency of anti-hyperuricemia drug (Allopurinol, AP) could be controlled using the iontophoresis current of IPMNs system. The AP release amount could be increased to 1.54 mg with iontophoresis under constant voltage of 1.5 V for 30 min. In vivo transdermal delivery of AP on mice models using IPMNs system exhibited an effective anti-hyperuricemia response. The serum uric acid (SUA) level could be dropped to ∼ 158.2 μmol/L within 2 h, and maintaining for 7 h under the normal level, leading a long-term therapeutic effect. This IPMNs system exhibits a low cost, user-friendly, and active delivery, showing great potential for hyperuricemia self-administration.

Tailoring Design of Microneedles for Drug Delivery and Biosensing

Microneedles (MNs) are emerging as versatile tools for both therapeutic drug delivery and diagnostic monitoring. Unlike hypodermic needles, MNs achieve these applications with minimal or no pain and customizable designs, making them suitable for personalized medicine. Understanding the key design parameters and the challenges during contact with biofluids is crucial to optimizing their use across applications. This review summarizes the current fabrication techniques and design considerations tailored to meet the distinct requirements for drug delivery and biosensing applications. We further underscore the current state of theranostic MNs that integrate drug delivery and biosensing and propose future directions for advancing MNs toward clinical use.

Microneedles at the Forefront of Next Generation Theranostics

Theranostics, combining therapeutic and diagnostic functions, marks a revolutionary advancement in modern medicine, with microneedle technology at its forefront. This review explores the substantial developments and multifaceted applications of microneedles, which have evolved from basic transdermal drug delivery devices to sophisticated diagnostic and therapeutic platforms. Microneedles enhance access to biomarkers via interstitial fluid, enabling real-time monitoring of physiological conditions, such as glucose and hormone levels, thus facilitating continuous health tracking. The evolution of microneedle design from solid to dissolvable forms broadens their utility from mere drug delivery to complex sensing and therapeutic applications, including insulin delivery for diabetes management, vaccination, and gene therapy. This paper delves into the integration of microneedles with wearable technologies, highlighting their role in closed-loop systems that combine real-time monitoring with dynamic, precise therapeutic delivery. By addressing gaps in the literature regarding their integrated diagnostic and treatment capabilities, this review underscores the pivotal role of microneedles in personalizing medicine. It concludes with a visionary perspective on the future trajectory of microneedle technology, emphasizing its potential to revolutionize therapeutic strategies through enhanced efficacy, safety, and patient compliance.

Toward precision medicine: End-to-end design and construction of integrated microneedle-based theranostic systems

With the growing demand for precision medicine and advancements in microneedle technology, microneedle-based drug delivery systems have evolved into integrated theranostic platforms. However, the development of these systems is currently limited by the absence of clear conclusions and standardized construction strategies. The end-to-end concept offers an innovative approach to theranostic systems by creating a seamless process that integrates target sampling, sensing, analysis, and on-demand drug delivery. This approach optimizes each step based on data from the others, effectively eliminating the traditional separation between drug delivery and disease monitoring. Furthermore, by incorporating artificial intelligence and machine learning, these systems can enhance reliability and efficiency in disease management, paving the way for more personalized and effective healthcare solutions. Based on the concept of end-to-end and recent advancements in theranostic systems, nanomaterials, electronic components, micro-composites, and data science, we propose a modular strategy for constructing integrated microneedle-based theranostic systems by detailing the methods and functions of each critical component, including monitoring, decision-making, and on-demand drug delivery units, though the total number of units might vary depending on the specific application. Notably, decision-making units are emerging trends for fully automatic and seamless systems and featured for integrated microneedle-based theranostic systems, which serve as a bridge of real-time monitoring, on-demand drug delivery, advanced electronic engineering, and data science for personalized disease management and remote medical application. Additionally, we discuss the challenges and prospects of integrated microneedle-based theranostic systems for precision medicine and clinical application.

Physical stimuli-responsive polymeric patches for healthcare

Many chronic diseases have become severe public health problems with the development of society. A safe and efficient healthcare method is to utilize physical stimulus-responsive polymer patches, which may respond to physical stimuli, including light, electric current, temperature, magnetic field, mechanical force, and ultrasound. Under certain physical stimuli, these patches have been widely used in therapy for diabetes, cancer, wounds, hair loss, obesity, and heart diseases since they could realize controllable treatment and reduce the risks of side effects. This review sketches the design principles of polymer patches, including composition, properties, and performances. Besides, control methods of using different kinds of physical stimuli were introduced. Then, the fabrication methods and characterization of patches were explored. Furthermore, recent applications of these patches in the biomedical field were demonstrated. Finally, we discussed the challenges and prospects for its clinical translation. We anticipate that physical stimulus-responsive polymer patches will open up new avenues for healthcare by acting as a platform with multiple functions.

Microneedles Constructed by Swellable Hydrogels Loaded with Celastrol for Efficient Treatment of Skin Infections Induced by Drug-Resistant Bacterial Strains

The urgent need for new antimicrobial drugs arises from the limited efficacy of traditional antibiotics against emerging drug-resistant strains. Celastrol (CSL) demonstrates an exceptional antibacterial property that remains unaffected by bacterial resistance, but its poor water solubility limits its wide applications. This study uses the hydrophobic inner cavity of mono-(6-diethylenetriamine-6-deoxy)-β-cyclodextrin (mβ-CD) (a derivative of cyclodextrin) to encapsulate CSL, constructing an inclusion complex (CSL@mβ-CD) to enhance the water solubility of CSL. The obtained inclusion complex is further incorporated into a swellable hydrogel microneedle (MN) to obtain CSL@mβ-CD/MN. The fabricated CSL@mβ-CD/MN can enable the sustained release of CSL, achieving effective bacterial eradication at infected sites. In vivo experiments demonstrate that CSL@mβ-CD/MN has a remarkable efficacy in the treatment of methicillin-resistant Staphylococcus aureus-induced subcutaneous abscesses and wound infections. Specifically, CSL@mβ-CD/MN can effectively penetrate the stratum corneum of the skin to realize rapid elimination of the bacteria in wounds. Moreover, CSL@mβ-CD/MN can efficiently scavenge reactive oxygen species, promote M2 polarization of macrophages, and relieve local inflammation at the wound sites. These results reveal that CSL@mβ-CD/MN holds great promise in the clinical treatment of acute skin infections induced by drug-resistant bacteria.

Current Status of Microneedle Array Technology for Therapeutic Delivery: From Bench to Clinic

In recent years, microneedle (MN) patches have emerged as an alternative technology for transdermal delivery of various drugs, therapeutics proteins, and vaccines. Therefore, there is an urgent need to understand the status of MN-based therapeutics. The article aims to illustrate the current status of microneedle array technology for therapeutic delivery through a comprehensive review. However, the PubMed search was performed to understand the MN's therapeutics delivery status. At the same time, the search shows the number no of publications on MN is increasing (63). The search was performed with the keywords "Coated microneedle," "Hollow microneedle," "Dissolvable microneedle," and "Hydrogel microneedle," which also shows increasing trend. Similarly, the article highlighted the application of different microneedle arrays for treating different diseases. The article also illustrated the current status of different phases of MN-based therapeutics clinical trials. It discusses the delivery of different therapeutic molecules, such as drug molecule delivery, using microneedle array technology. The approach mainly discusses the delivery of different therapeutic molecules. The leading pharmaceutical companies that produce the microneedle array for therapeutic purposes have also been discussed. Finally, we discussed the limitations and future prospects of this technology.

Glucose Oxidase-Immobilized Dually-Crosslinked Nanogels for Rapid-Responsive Insulin Delivery

Despite the potential benefits of close-looped insulin delivery systems in regulating glycemic homeostasis and effectively alleviating diabetes, they still encounter challenges such as limited effectiveness in preventing low glycemic episodes due to sluggish glucose response, and issues with the instability of enzymes and carriers. In this study, dually-crosslinked and glucose oxidase (GOx)-immobilized insulin nanogels (DC-NGs@Ins) are developed for rapid-responsive and sustained hypoglycemic therapy. The DC-NGs@Ins with the phenylborate ester linker enabled the insulin release in a close-looped fashion, and moreover, immobilized GOx-generated hydrogen peroxide (H2O2) by consuming the glucose, which can further bind to phenylborate ester for enhancing glucose response and accelerating the insulin release. The dually-crosslinked structure (phenylboronic ester and UV-crosslinking) effectively minimized the initial burst release of insulin, thus preventing the potential risk of hypoglycemia. More interestingly, GOx immobilized in the nanogels mitigated GOx leakage and enhanced its multiple utilization compared to free GOx. In vivo study demonstrated that DC-NGs@Ins effectively maintained glycemic levels (BGLs) below 200 mg dL-1 for at least 8 h compared to singly-crosslinked nanogels (SC-NGs@Ins). Therefore, this intelligent insulin delivery system shows potential applications in diabetes treatment.

A Glucose-Responsive Glucagon-Micelle for the Prevention of Hypoglycemia

While glucose-responsive insulin delivery systems are in widespread clinical use to treat insulin insufficiency, the on-demand supplementation of glucagon for acute hypoglycemia treatment remains understudied. A self-regulated glucagon release material is highly desired to mitigate the potential risks of severe insulin-induced hypoglycemia. Here, we describe a glucose-responsive polymeric nanosystem with glucagon covalently grafted to the end-group. Under normoglycemic conditions, phenylboronic acid units in the polymer chain reversibly bind glucose, triggering self-assembly of the conjugate into micelles. During hypoglycemia, however, the micelle disassembles into its original, unimeric state, revealing the active glucagon conjugate. The formulation showed a 5-fold increase in activity compared to native glucagon when tested in vitro. Glucagon-loaded micelles injected into mice prevented or reversed deep hypoglycemia when administered prior to or during an insulin challenge. Glucagon release was only observed at or below the counterregulatory threshold and not during normoglycemia or moderate hypoglycemia. The in vivo acute and chronic toxicity analysis, along with μPET/μCT imaging, established the biosafety profile of this formulation and demonstrated no organ accumulation. This proof-of-concept work is the first step toward development of a translational, stimuli-responsive glucagon delivery platform to control glycemia.

Promising strategies for smart insulin delivery system: Glucose-sensitive microneedle

The diabetes treatment landscape is rapidly evolving towards intelligent and precise therapeutic interventions. Among these advancements, glucose-sensitive microneedle patches (GSMPs), which can automatically adjust the transdermal release rate of insulin based on glucose concentrations, are emerging as a promising strategy. In this work, a new classification method has been proposed for GSMPs, categorizing them into integrated, all-in-one, and core-shell structures. The working mechanism and performance of GSMPs are thoroughly analyzed to compare the advantages and disadvantages of these three forms. The correlation between glucose-sensitive performance and normal blood glucose maintenance time (NGT) is further explored. Our findings indicate that all-in-one GSMPs demonstrate a positive correlation between in vitro glucose-sensitive controlled-release performance and NGT, unlike assembled GSMPs, where the performance is influenced by the matrix material and crosslinking factors. Simultaneously, challenges in clinical translation and future development trends are discussed from a patient's perspective. In summary, the new classification method, in-depth explanation of mechanisms, and analysis of challenges in this work contribute to a better understanding of the field of GSMPs and provide guidance for the development of more advanced and efficient GSMPs.

Analysis of Glucose Responsive Glucagon Therapeutics using Computational Models of the Glucoregulatory System

Glucose-responsive glucagon (GRG) therapeutics are a promising technology for reducing the risk of severe hypoglycemia as a complication of diabetes mellitus. Herein, the performance of candidate GRGs in the literature by modeling the kinetics of activation and connecting them as input into physiological glucoregulatory models is evaluated and projected the two distinct GRG designs, experimental results reported in Wu et al. (GRG-I) and Webber et al. (GRG-II) is considered. Both are evaluated using a multi-compartmental glucoregulatory model (IMPACT) and used to compare in-vivo experimental data of therapeutic performance in rats and mice. For GRG-I and GRG-II, the total integrated glucose material balances are overestimated by 41.5% ± 14% and underestimated by 24.8% ± 16% compared to in-vivo time-course data, respectively. These large differences to the relatively simple computational descriptions of glucagon dynamics in the model, which underscores the urgent need for improved glucagon models is attributed. Additionally, therapeutic insulin and glucagon infusion pumps are modeled for type 1 diabetes mellitus (T1DM) human subjects to extend the results to additional datasets. These observations suggest that both the representative physiological and non-physiological models considered in this work require additional refinement to successfully describe clinical data that involve simultaneous, coupled insulin, glucose, and glucagon dynamics.

Visualization of the degradation of long-acting microneedles and correlation of drug release in vivo based on FRET mechanism

This study introduces a live imaging technique for real-time, non-invasive monitoring of drug release from long-acting microneedles using FRET (Fluorescence Resonance Energy Transfer). Employing Cy5.5 and Cy7 as FRET pairs and levonorgestrel as the model drug, we fabricated microneedles with varying PLGA molecular weights, demonstrating distinct release profiles. The FRET-PLGA-10-MN demonstrated a rapid drug release profile, reaching nearly complete release within a two-day period, while FRET-PLGA-30-MN showed a sustained release over four days. Sensitized Emission FRET (SE-FRET) optimized the imaging process, providing a robust correlation between FRET signals and drug absorption. This method surpasses traditional pharmacokinetic studies by offering a more efficient and comprehensive analysis of microneedle release dynamics in vivo, paving the way for enhanced long-acting microneedle design and therapeutic outcomes. STATEMENT OF SIGNIFICANCE: 1. FRET technology was applied to microneedle drug delivery system for the first time, which realized real-time, quantitative and non-invasive monitoring of drug release process. 2. The long-term microneedle technique was combined with sensitized emission method, and the FRET remaining ratio was innovatively used to investigate the FRET characteristics of microneedles, and the fluorescence ratio of FRET and donor double-channel was quantitatively calculated. 3. The correlation between visual fluorescence images of FRET effect and semi-quantitative calculation results based on fluorescence intensity and drug release in vivo with drug-loaded microneedles was analyzed.

Advances of Smart Stimulus-Responsive Microneedles in Cancer Treatment

Microneedles (MNs) have emerged as a highly promising technology for delivering drugs via the skin. They provide several benefits, including high drug bioavailability, non-invasiveness, painlessness, and high safety. Traditional strategies for intravenous delivery of anti-tumor drugs have risks of systemic toxicity and easy development of drug resistance, while MN technology facilitates precise delivery and on-demand release of drugs in local tissues. In addition, by further combining with stimulus-responsive materials, the construction of smart stimulus-responsive MNs can be achieved, which can respond to specific physical/chemical stimuli from the internal or external environment, thereby further improving the accuracy of tumor treatment and reducing toxicity to surrounding tissues/cells. This review systematically summarizes the classification, materials, and reaction mechanisms of stimulus-responsive MNs, outlines the benefits and challenges of various types of MNs, and details their application and latest progress in cancer treatment. Finally, the development prospects of smart MNs in tumor treatment are also discussed, bringing inspiration for future precision treatment of tumors.

Research Progress of Hydrogel Microneedles in Wound Management

Microneedles are a novel drug delivery system that offers advantages such as safety, painlessness, minimally invasive administration, simplicity of use, and controllable drug delivery. As a type of polymer microneedle with a three-dimensional network structure, hydrogel microneedles (HMNs) possess excellent biocompatibility and biodegradability and encapsulate various therapeutic drugs while maintaining drug activity, thus attracting significant attention. Recently, they have been widely employed to promote wound healing and have demonstrated favorable therapeutic effects. Although there are reviews about HMNs, few of them focus on wound management. Herein, we present a comprehensive overview of the design and preparation methods of HMNs, with a particular emphasis on their application status in wound healing, including acute wound healing, infected wound healing, diabetic wound healing, and scarless wound healing. Finally, we examine the advantages and limitations of HMNs in wound management and provide suggestions for future research directions.

A glycopolymersome strategy for 'drug-free' treatment of diabetic nephropathy

Diabetic nephropathy is a severe complication of diabetes. Treatment of diabetic nephropathy is an important challenge due to persistent hyperglycemia and elevated levels of reactive oxygen species (ROS) in the kidney. Herein, we designed a glycopolymersome that can treat type 2 diabetic nephropathy by effectively inhibiting hyperglycemia and ROS-associated diabetic nephropathy pathogenesis. The glycopolymersome is self-assembled from phenylboronic acid derivative-containing copolymer, poly(ethylene oxide)45-block-poly[(aspartic acid)13-stat-glucosamine24-stat-(phenylboronic acid)18-stat-(phenylboronic acid pinacol ester)3] [PEO45-b-P(Asp13-stat-GA24-stat-PBA18-stat-PAPE3)]. PBA segment can reversibly bind blood glucose or GA segment for long-term regulation of blood glucose levels; PAPE segment can scavenge excessive ROS for renoprotection. In vitro studies confirmed that the glycopolymersomes exhibit efficient blood glucose responsiveness within 2 h and satisfactory ROS-scavenging ability with 500 μM H2O2. Moreover, the glycopolymersomes display long-acting regulation of blood glucose levels in type 2 diabetic nephropathy mice within 32 h. Dihydroethidium staining revealed that these glycopolymersomes reduced ROS to normal levels in the kidney, which led to 61.7% and 76.6% reduction in creatinine and urea levels, respectively, along with suppressing renal apoptosis, collagen accumulation, and glycogen deposition in type 2 diabetic nephropathy mice. Notably, the polypeptide-based glycopolymersome was synthesized by ring-opening polymerization (ROP) of N-carboxyanhydrides (NCAs), thereby exhibiting favorable biodegradability. Overall, we proposed a new glycopolymersome strategy for 'drug-free' treatment of diabetic nephropathy, which could be extended to encompass the design of various multifunctional nanoparticles targeting diabetes and its associated complications.

Dually crosslinked degradable polyionic micelles for sustained glucose-responsive insulin release

Glucose -sensitive delivery systems hold great promise as a therapeutic approach for high-incidence diabetes owing to their ability to release insulin whenever elevated glycemia is detected. However, they are unstable in a hyperglycemic environment, which leads to short-term sustained insulin release. Herein, we designed dually crosslinked insulin polyionic micelles (DCM@insulin) based on triblock polymers of o-glycol and phenylboronic acid-functionalized poly(ethylene glycol)-poly(dimethylamino carbonate)-poly(dimethylamino-trimethylene carbonate) (mPEG-P(AC-co-MPD)-PDMAC and mPEG-P(AC-co-MAPBA)-PDMATC, respectively) for sustained glucose-responsive insulin release. DCM@insulin with a phenylboronic acid ester structure (first crosslinking structure) enhanced glycemic responsiveness by regulating insulin release in a hyperglycemic environment. Additionally, the UV-crosslinking structure (second crosslinking structure) formed by the residual double bonds in AC units endowed DCM@insulin with the ability to effectively protect the loaded insulin against protease degradation and avoid burst release under multiple insulin release. The in vivo findings demonstrated that DCM@insulin effectively maintained glycemic levels (BGLs) within the normal range for 6 h in comparison to single-crosslinked micelles (SCM@insulin). Therefore, the glucose-responsive and dually crosslinked polyionic micelle system exhibits potential as a viable option for the treatment of diabetes.

Rapid Correction of the Hypoglycemia State in Nonhuman Primates Using a Glucagon Long-Dissolving Microneedle Patch

The timely administration of glucagon is a standard clinical practice for the treatment of severe hypoglycemia. However, the process involves cumbersome steps, including the reconstitution of labile glucagon and filling of the syringe, which cause considerable delays in emergency situations. Moreover, multiple dosages are often required to prevent the recurrence of the hypoglycemic episode because of the short half-life of glucagon in plasma. Herein, we develop a glucagon-loaded long-dissolving microneedle (GLMN) patch that exhibits the properties of fast onset and sustained activity for the effective treatment of severe hypoglycemia. Three types of MN patches were fabricated with different dimensions (long, medium, and short). The longer MN patch packaged a higher dosage of glucagon and exhibited supreme mechanical strength compared to the shorter one. Additionally, the longer MN patch could insert more deeply into the skin, resulting in higher permeability of glucagon across the skin tissue and more rapid systemic absorption as compared with the shorter MN patch. The GLMN patch was observed to reverse the effects of hypoglycemia within 15 min of application in animal models (specifically, rat and rhesus monkey models) and maintained long-term glycemic control, owing to highly efficient drug permeation and the drug reservoir effect of the MN base. The current study presents a promising strategy for the rapid reversal of severe hypoglycemia that exhibits the desirable properties of easy use, high efficiency, and sustained action.

X-ray-activated polymerization expanding the frontiers of deep-tissue hydrogel formation

Photo-crosslinking polymerization stands as a fundamental pillar in the domains of chemistry, biology, and medicine. Yet, prevailing strategies heavily rely on ultraviolet/visible (UV/Vis) light to elicit in situ crosslinking. The inherent perils associated with UV radiation, namely the potential for DNA damage, coupled with the limited depth of tissue penetration exhibited by UV/Vis light, severely restrict the scope of photo-crosslinking within living organisms. Although near-infrared light has been explored as an external excitation source, enabling partial mitigation of these constraints, its penetration depth remains insufficient, particularly within bone tissues. In this study, we introduce an approach employing X-ray activation for deep-tissue hydrogel formation, surpassing all previous boundaries. Our approach harnesses a low-dose X-ray-activated persistent luminescent phosphor, triggering on demand in situ photo-crosslinking reactions and enabling the formation of hydrogels in male rats. A breakthrough of our method lies in its capability to penetrate deep even within thick bovine bone, demonstrating unmatched potential for bone penetration. By extending the reach of hydrogel formation within such formidable depths, our study represents an advancement in the field. This application of X-ray-activated polymerization enables precise and safe deep-tissue photo-crosslinking hydrogel formation, with profound implications for a multitude of disciplines.

Microneedle Sensors for Point-of-Care Diagnostics

Point-of-care (POC) has the capacity to support low-cost, accurate and real-time actionable diagnostic data. Microneedle sensors have received considerable attention as an emerging technique to evolve blood-based diagnostics owing to their direct and painless access to a rich source of biomarkers from interstitial fluid. This review systematically summarizes the recent innovations in microneedle sensors with a particular focus on their utility in POC diagnostics and personalized medicine. The integration of various sensing techniques, mostly electrochemical and optical sensing, has been established in diverse architectures of "lab-on-a-microneedle" platforms. Microneedle sensors with tailored geometries, mechanical flexibility, and biocompatibility are constructed with a variety of materials and fabrication methods. Microneedles categorized into four types: metals, inorganics, polymers, and hydrogels, have been elaborated with state-of-the-art bioengineering strategies for minimally invasive, continuous, and multiplexed sensing. Microneedle sensors have been employed to detect a wide range of biomarkers from electrolytes, metabolites, polysaccharides, nucleic acids, proteins to drugs. Insightful perspectives are outlined from biofluid, microneedles, biosensors, POC devices, and theragnostic instruments, which depict a bright future of the upcoming personalized and intelligent health management.

PVA-based bulk microneedles capable of high insulin loading and pH-triggered degradation for multi-responsive and sustained hypoglycemic therapy

"Closed-loop" insulin-loaded microneedle patche shows great promise for improving therapeutic outcomes and life quality for diabetes patients. However, it is typically hampered by limited insulin loading capacity, random degradation, and intricate preparation procedures for the independence of the "closed-loop" bulk microneedles. In this study, we combined the solubility of microneedles and "closed-loop" systems and designed poly(vinyl alcohol)-based bulk microneedles (MNs@GI) through in situ photopolymerization for multi-responsive and sustained hypoglycemic therapy, which significantly simplified the preparation process and improved insulin loading. GOx/insulin co-encapsulated MNs@GI with a phenylboronic ester structure improved glycemic responsiveness to control the insulin release under high glucose conditions and reduced inflammation risk in the normal skin. MNs@GI could further degrade to increase insulin release due to the crosslinked acetal-linkage hydrolysis in the presence of gluconic acid, which was caused by GOx-mediated glucose-oxidation in a hyperglycemic environment. The in vivo results showed that MNs@GI effectively regulated glycemic levels within the normal range for approximately 10 h compared to that of only insulin-loaded microneedles (MNs@INS). Consequently, the highly insulin-loaded, multi-responsive, and pH-triggered MN system has tremendous potential for diabetes treatment.

Microneedle and Polymeric Films: Delivery of Proteins, Peptides and Nucleic Acids

In the last 20 years, protein, peptide and nucleic acid-based therapies have become the fastest growing sector in the pharmaceutical industry and play a vital role in disease therapy. However, the intrinsic sensitivity and large molecular sizes of biotherapeutics limit the available routes of administration. Currently, the main administration routes of biomacromolecules, such as parenteral, oral, pulmonary, nasal, rectal and buccal routes, each have their limitations. Several non-invasive strategies have been proposed to overcome these challenges. Researchers were particularly interested in microneedles (MNs) and polymeric films because of their less invasiveness, convenience and greater potential to preserve the bioactivity of biotherapeutics. By facilitating with MNs and polymeric films, biomacromolecules could provide significant benefits to patients suffering from various diseases such as cancer, diabetes, infectious and ocular diseases. However, before these devices can be used on patients, how to upscale MN manufacture in a cost-effective and timely manner, as well as the long-term safety of MN and polymeric film applications necessitates further investigation.

Tailoring Hyaluronic Acid Hydrogels for Biomedical Applications

Hyaluronic acid (HA) is an attractive anionic polysaccharide polymer with inherent pharmacological properties and versatile chemical groups for modification. Due to their water retention ability, biocompatibility, biodegradation, cluster of differentiation‐44 targeting, and highly designable capacity, HA hydrogels have been an emerging biomaterial, showing tailoring performance in terms of chemical modifications and hydrogel forms. Various preparation technologies have been developed for the fabrication of the tailoring HA hydrogels with unique structures and functions. They have been utilized in diverse biomedical applications like drug delivery and tissue engineering scaffolds. Herein, this review comprehensively summarizes the HA derivatives with different molecule weights and functional modifications. Then the various fabrication methods to obtain tailoring hydrogels in the forms of nanogel, nanofiber, microparticle, microneedle patch, injectable hydrogel, and scaffold are reviewed as well. The emphasis is focused on the shining biomedical applications of these tailoring HA hydrogels in anti‐bacteria, anti‐inflammation, wound healing, cancer treatment, regenerative medicine, psoriasis treatment, diagnosis, etc. The potentials and prospects are subsequently given to inspire further investigation, aiming at accelerating product translation from research to clinic.

Hydrogel-Based Microneedle as a Drug Delivery System

The skin is considered the largest and most accessible organ in the human body, and allows the use of noninvasive and efficient strategies for drug administration, such as the transdermal drug delivery system (TDDS). TDDSs are systems or patches, with the ability and purpose to deliver effective and therapeutic doses of drugs through the skin. Regarding the specific interaction between hydrogels (HG) and microneedles (MNs), we seek to find out how this combination would be applied in the context of drug delivery, and we detail some possible advantages of the methods used. Depending on the components belonging to the HG matrix, we can obtain some essential characteristics that make the combination of hydrogels-microneedles (HG-MNs) very advantageous, such as the response to external stimuli, among others. Based on multiple characteristics provided by HGMNs that are depicted in this work, it is possible to obtain unique properties that include controlled, sustained, and localized drug release, as well as the possibility of a synergistic association between the components of the formulation and the combination of more than one bioactive component. In conclusion, a system based on HG-MNs can offer many advantages in the biomedical field, bringing to light a new technological and safe system for improving the pharmacokinetics and pharmacodynamics of drugs and new treatment perspectives.

"Smart" Matrix Microneedle Patch Made of Self-Crosslinkable and Multifunctional Polymers for Delivering Insulin On-Demand

A transdermal patch that delivers insulin at high glucose concentrations can offer tremendous advantages to ease the concern of safety and improve the quality of life for people with diabetes. Herein, a novel self-crosslinkable and glucose-responsive polymer-based microneedle patch (MN) is designed to deliver insulin at hyperglycemia. The microneedle patch is made of hyaluronic acid polymers functionalized with dopamine and 4-amino-3-fluorophenylboronic acid (AFBA) that can be quickly crosslinked upon mixing of the polymer solutions in the absence of any chemicalcrosslinking agents or organic solvents. The catechol groups in the dopamine (DA) units form covalent crosslinkages among themselves by auto-oxidation and dynamic crosslink with phenylboronic acid (PBA) via complexation. The reversible crosslinkages between catechol and boronate decrease with increasing glucose concentration leading to higher swelling and faster insulin release at hyperglycemia as compared to euglycemia. Such superior glucose-responsive properties are demonstrated by in vitro analyses and in vivo efficacy studies. The hydrogel polymers also preserve native structure and bioactivity of insulin, attributable to the interaction of hyaluronic acid (HA) with insulin molecules, as revealed by experiments and molecular dynamics simulations. The simplicity in the design and fabrication process, and glucose-responsiveness in insulin delivery impart the matrix microneedle (mMN) patch great potential for clinical translation.

A Cu@ZIF-8 encapsulated antibacterial and angiogenic microneedle array for promoting wound healing

Skin wounds caused by external injuries remain a serious challenge in clinical practice. Wound dressings that are antibacterial, pro-angiogenic, and have potent regeneration capacities are highly desirable for wound healing. In this study, a minimally invasive and wound-friendly Cu@ZIF-8 encapsulated PEGDA/CMCS microneedle (MN) array was fabricated using the molding method to promote wound healing. The MNs had good biocompatibility, excellent mechanical strength, as well as strong antibacterial properties and pro-angiogenic effects. When incubated with H2O2, Cu@ZIF-8 nanoparticles generated reactive oxygen species, which contributed to their antibacterial properties. Due to the oxidative stress of the cupric ions released from Cu@ZIF-8 and the anti-bacterial capability of the PEGDA/CMCS hydrogel scaffold, such an MN array presents excellent antibacterial activity. Moreover, with the continuous release of Cu ions from the scaffold, such MNs are effective in terms of promoting angiogenesis. With considerable biocompatibility and a minimally invasive approach, the degradable MN array composed of PEGDA/CMCS possessed superior capabilities to continuously and steadily release the loaded ingredients and avoid secondary damage to the wound. Benefiting from these features, the Cu@ZIF-8 encapsulated degradable MN array can dramatically accelerate epithelial regeneration and neovascularization. These results indicated that the combination of Cu@ZIF-8 and degradable MN arrays is valuable in promoting wound healing, which opened a new window for treatment of skin defection.

Advances in Intelligent Stimuli-Responsive Microneedle for Biomedical Applications

Microneedles (MNs) are a new type of drug delivery method that can be regarded as an alternative to traditional transdermal drug delivery systems. Recently, MNs have attracted widespread attention for their advantages of effectiveness, safety, and painlessness. However, the functionality of traditional MNs is too monotonous and limits their application. To improve the efficiency of disease treatment and diagnosis by combining the advantages of MNs, the concept of intelligent stimulus-responsive MNs is proposed. Intelligent stimuli-responsive MNs can exhibit unique biomedical functions according to the internal and external environment changes. This review discusses the classification and principles of intelligent stimuli-responsive MNs, such as magnet, temperature, light, electricity, reactive oxygen species, pH, glucose, and protein. This review also highlights examples of intelligent stimuli-responsive MNs for biomedical applications, such as on-demand drug delivery, tissue repair, bioimaging, detection and monitoring, and photothermal therapy. These intelligent stimuli-responsive MNs offer the advantages of high biocompatibility, targeted therapy, selective detection, and precision treatment. Finally, the prospects and challenges for the application of intelligent stimuli-responsive MNs are discussed.

A multifunctional 'golden cicada' nanoplatform breaks the thermoresistance barrier to launch cascade augmented synergistic effects of photothermal/gene therapy

BACKGROUND

Photothermal therapy (PTT) is taken as a promising strategy for cancer therapy, however, its applicability is hampered by cellular thermoresistance of heat shock response and insufficient accumulation of photothermal transduction agents in the tumor region. In consideration of those limitations, a multifunctional "Golden Cicada" nanoplatform (MGCN) with efficient gene delivery ability and excellent photothermal effects is constructed, overcoming the thermoresistance of tumor cells and improving the accumulation of indocyanine green (ICG).

RESULTS

Down-regulation of heat shock protein 70 (HSP70) makes tumor cells more susceptible to PTT, and a better therapeutic effect is achieved through such cascade augmented synergistic effects. MGCN has attractive features with prolonged circulation in blood, dual-targeting capability of CD44 and sialic acid (SA) receptors, and agile responsiveness of enzyme achieving size and charge double-variable transformation. It proves that, on the one hand, MGCN performs excellent capability for HSP70-shRNA delivery, resulting in breaking the cellular thermoresistance mechanism, on the other hand, ICG enriches in tumor site specifically and possesses a great thermal property to promoted PTT.

CONCLUSIONS

In short, MGCN breaks the protective mechanism of cellular heat stress response by downregulating the expression of HSP70 proteins and significantly augments synergistic effects of photothermal/gene therapy via cascade augmented synergistic effects.

Responsive Microneedles as a New Platform for Precision Immunotherapy

Microneedles are a well-known transdermal or transdermal drug delivery system. Different from intramuscular injection, intravenous injection, etc., the microneedle delivery system provides unique characteristics for immunotherapy administration. Microneedles can deliver immunotherapeutic agents to the epidermis and dermis, where immune cells are abundant, unlike conventional vaccine systems. Furthermore, microneedle devices can be designed to respond to certain endogenous or exogenous stimuli including pH, reactive oxygen species (ROS), enzyme, light, temperature, or mechanical force, thereby allowing controlled release of active compounds in the epidermis and dermis. In this way, multifunctional or stimuli-responsive microneedles for immunotherapy could enhance the efficacy of immune responses to prevent or mitigate disease progression and lessen systemic adverse effects on healthy tissues and organs. Since microneedles are a promising drug delivery system for accurate delivery and controlled drug release, this review focuses on the progress of using reactive microneedles for immunotherapy, especially for tumors. Limitations of current microneedle system are summarized, and the controllable administration and targeting of reactive microneedle systems are examined.

Implantable device with magnetically rotating disk for needle-free administrations of emergency drug

Prompt administration of first-aid drugs can save lives during medical emergencies such as anaphylaxis and hypoglycemia. However, this is often performed by needle self-injection, which is not easy for patients under emergency conditions. Therefore, we propose an implantable device capable of on-demand administration of first-aid drugs (i.e., the implantable device with a magnetically rotating disk [iMRD]), such as epinephrine and glucagon, via a noninvasive simple application of the magnet from the outside skin (i.e., the external magnet). The iMRD contained a disk embedded with a magnet, as well as multiple drug reservoirs that were sealed with a membrane, which was designed to rotate at a precise angle only when the external magnet was applied. During this rotation, the membrane on a designated single-drug reservoir was aligned and torn to expose the drug to the outside. When implanted in living animals, the iMRD, actuated by an external magnet, delivers epinephrine and glucagon, similar to conventional subcutaneous needle injections.

Nanoparticle surface decoration mediated efficient protein and peptide co-encapsulation with precise ratiometric control for self-regulated drug release

Accuratly controlling drug release from a smart "self-regulated" drug delivery system is still an ongoing challenge. Herein, we developed a surface decoration strategy to achieve an efficient drug encapsulation with precise ratiometric control. Thanks to the surface decoration with cationic carrier materials by electrostatic attraction, the surface properties of different protein and peptide nanoparticles were uniformed to those adsorbed carrier materials. These carrier materials endowed protein and peptide nanoparticles with good dispersity in the oil phase and significantly inhibited the drug transfer from oil to water. With uniform surface properties, we realized the co-encapsulation of multiple types of proteins and peptides with precise ratiometric control. The encapsulation efficiency was higher than 87.8% for insulin. After solidification, the adsorbed materials on the surface of nanoparticles formed a solid protection layer, which prolonged the mean residence time of insulin from 3.3 ± 0.1 h (for insulin solution) to 47.5 ± 1.3 h. In type 1 diabetes, the spermine-modified acetalated dextran microparticle co-loaded with insulin, glucose oxidase and catalase maintained the blood glucose level within the normal range for 7 days.

Microneedle-Mediated Transdermal Delivery of Biopharmaceuticals

Transdermal delivery provides numerous benefits over conventional routes of administration. However, this strategy is generally limited to a few molecules with specific physicochemical properties (low molecular weight, high potency, and moderate lipophilicity) due to the barrier function of the stratum corneum layer. Researchers have developed several physical enhancement techniques to expand the applications of the transdermal field; among these, microneedle technology has recently emerged as a promising platform to deliver therapeutic agents of any size into and across the skin. Typically, hydrophilic biomolecules cannot penetrate the skin by passive diffusion. Microneedle insertion disrupts skin integrity and compromises its protective function, thus creating pathways (microchannels) for enhanced permeation of macromolecules. Microneedles not only improve stability but also enhance skin delivery of various biomolecules. Academic institutions and industrial companies have invested substantial resources in the development of microneedle systems for biopharmaceutical delivery. This review article summarizes the most recent research to provide a comprehensive discussion about microneedle-mediated delivery of macromolecules, covering various topics from the introduction of the skin, transdermal delivery, microneedles, and biopharmaceuticals (current status, conventional administration, and stability issues), to different microneedle types, clinical trials, safety and acceptability of microneedles, manufacturing and regulatory issues, and the future of microneedle technology.

Composite Separable Microneedles for Transdermal Delivery and Controlled Release of Salmon Calcitonin for Osteoporosis Therapy

A composite separable microneedles (MNs) system consisting of silk fibroin (SF) needle tips and hyaluronic acid (HA) base is developed for transdermal delivery of salmon calcitonin (sCT) for therapy of osteoporosis. Poly(ethylene glycol) (PEG) is used to modulate the conformation structure of SF to achieve controllable sustained release of sCT. The prepared MNs can effectively penetrate the skin stratum corneum. After application to the skin, the HA base is dissolved within 2 min, allowing these SF drug depots to be implanted into the skin for controllable sustained release of sCT. The release kinetics of sCT can be controlled by regulating the conformation of SF with PEG and the interaction between sCT peptide and SF proteins. Compared with traditional needle injection, delivery of sCT using optimized HA-PEG/SF MNs shows better trabecular bone repair for ovariectomized-induced osteoporosis in mice. The proposed MNs system provides a new noninjection strategy for therapy of osteoporosis.

Microneedles loaded with glutathione-scavenging composites for nitric oxide enhanced photodynamic therapy of melanoma

Photodynamic therapy (PDT) represents an attractive promising route for melanoma treatment. However, its therapeutic efficacy is compromised by inefficient drug delivery and high glutathione (GSH) levels in cancer cells. To overcome these challenges, microneedles (MNs) system loaded with GSH-scavenging nanocomposites was presented for nitric oxide (NO) enhanced PDT. The nanocomposites consisted of S-nitroso-N-acrylate penicillamine (SNAP; a NO donor) grafted fourth-generation polyamide amine dendrimer (G4) and chlorin e6 (Ce6). Upon local insertion of polyvinylpyrrolidone MNs, G4-SNAP/Ce6 composites were fast delivered and significantly amplified the therapeutic effects during PDT, via GSH depletion and reactive nitrogen species generation. Even with a single administration and low power light exposure, MNs with G4-SNAP/Ce6 effectively halt the tumor progression. The system demonstrated better cancer ablation efficacy than Ce6 alone toward melanoma. The strategy may inspire new ideas for future PDT-related therapy for skin tumors.

Glucose-responsive microneedle patch for closed-loop dual-hormone delivery in mice and pigs

Insulin and glucagon secreted from the pancreas with dynamic balance play a vital role in regulating blood glucose levels. Although distinct glucose-responsive insulin delivery systems have been developed, the lack of a self-regulated glucagon release module limits their clinical applications due to the potential risk of hypoglycemia. Here, we describe a transdermal polymeric microneedle patch for glucose-responsive closed-loop insulin and glucagon delivery to achieve glycemic regulation with minimized risk of hypoglycemia. The glucose-responsive phenylboronic acid units can bind to glucose to reversibly shift the net charge (from positive to negative) of the entire polymeric matrix within microneedles. Therefore, the release ratio of the negatively charged insulin and the positively charged glucagon analog from the patch can be dynamically tuned upon the fluctuation of blood glucose levels to realize glycemic homeostasis. In both chemically induced type 1 diabetic mouse and minipig models, this glucose-responsive dual-hormone microneedle patch demonstrated tight long-term regulation in blood glucose levels (>24 hours in minipigs).

Transdermal Insulin Delivery and Microneedles-based Minimally Invasive Delivery Systems

Diabetes has become a serious threat to human health, causing death and pain to numerous patients. Transdermal insulin delivery is a substitute for traditional insulin injection to avoid pain from the injection. Transdermal methods include non-invasive and invasive methods. As the non-invasive methods could hardly get through the stratum corneum, minimally invasive devices, especially microneedles, could enhance the transappendageal route in transcutaneous insulin delivery, and could act as connectors between the tissue and outer environment or devices. Microneedle patches have been in quick development in recent years and with different types, materials and functions. In those patches, the smart microneedle patch could perform as a sensor and reactor responding to glucose to regulate the blood level. In the smart microneedles field, the phenylboronic acid system and the glucose oxidase system have been successfully applied on the microneedle platform. Insulin transdermal delivery strategy, microneedles technology and smart microneedles' development would be discussed in this review.

Shrinking Fabrication of a Glucose-Responsive Glucagon Microneedle Patch

A microdevice that offers glucagon supplements in a safe, non-invasive, and glucose-responsive manner is ideal for avoiding fatal hypoglycemia consequences from insulin overdosage during daily diabetes treatment. However, mold-assisted microfabrication of biomedical materials or devices typically needs high-resolution laser ablation to scale down structural design. In addition, the majority of the polymeric drug delivery materials being used to fabricate devices are dissolvable or deformable in aqueous environments, which restricts washing-based cleaning and purification procedures post shape fixation. This study leverages the design flexibility of 3D printing-assisted mold casting and presents a shrinking microfabrication approach that allows subsequent washing procedures to remove toxic monomer residues during polymerization. The feasibility of this approach is demonstrated by developing a glucose-responsive transdermal glucagon microneedle patch through matrix volume change-mediated release kinetic control. Shown in the type 1 diabetic mouse model, this transdermal patch can reverse the occurrence of hypoglycemia while lowering the risk of monomer residue-induced irritation during treatment. Freeing from the restrain of molding resolution for microstructure design, this shrinking methodology further provides an insight into post-fabrication purifications of biomedical materials.

Hydrogel Microneedle-Assisted Assay Integrating Aptamer Probes and Fluorescence Detection for Reagentless Biomarker Quantification

Analyzing interstitial fluid (ISF) via microneedle (MN) devices enables patient health monitoring in a minimally invasive manner and in point-of-care settings. However, most MN-based diagnostic approaches require complicated fabrication processes and postprocessing of the extracted ISF or are limited to detection of electrochemically active biomarkers. Here, we show on-needle measurement of target analytes by integrating hydrogel microneedles with aptamer probes as the recognition elements. Fluorescently tagged aptamer probes are chemically attached to the hydrogel matrix using a simple and novel approach, while a cross-linked patch is formed. For reagentless detection, we employ a strand displacement strategy where fluorophore-conjugated aptamers are hybridized with a DNA competitor strand conjugated to a quencher molecule. The assay is utilized for rapid (2 min) measurement of glucose, adenosine triphosphate, l-tyrosinamide, and thrombin ex vivo. Furthermore, the system enables specific and sensitive quantification of rising and falling concentrations of glucose in an animal model of diabetes to track hypoglycemia, euglycemia, and hyperglycemia conditions. Our assay can be applied for rapid measurement of a diverse range of biomarkers, proteins, or small molecules, introducing a generalizable platform for biomolecule quantification, and has the potential to improve the quality of life of patients who are in need of close monitoring of biomarkers of health and disease.

Advances and challenges in developing smart, multi-functional microneedles for biomedical applications

Microneedles (MNs) have been developed as minimally invasive tools for diagnostic and therapeutic applications. However, in recent years, there has been an increasing interest in developing smart multi-functional MN devices to provide automated and closed-loop systems for body fluid extraction, biosensing, and drug delivery in a stimuli-responsive manner. Although this technology is still in its infancy and far from being translated into the clinic, preclinical trials have shown some promise for the broad applications of multi-functional MN devices. The main challenge facing the fabrication of smart MN patches is the integration of multiple modules, such as drug carriers, highly sensitive biosensors, and data analyzers in one miniaturized MN device. Researchers have shown the feasibility of creating smart MNs by integrating stimuli-responsive biomaterials and advanced microscale technologies, such as microsensors and microfluidic systems, to precisely control the transportation of biofluids and drugs throughout the system. These multi-functional MN devices can be envisioned in two distinct strategies. The first type includes individual drug delivery and biosensing MN units with a microfluidic system and a digital analyzer responsible for fluid transportation and communication between these two modules. The second type relies on smart biomaterials that can function as drug deliverers and biosensors by releasing drugs in a stimuli-responsive manner. These smart biomaterials can undergo structural changes when exposed to external stimuli, such as pH and ionic changes, mimicking the biological systems. Studies have demonstrated a high potential of hydrogel-based MN devices for a wide variety of biomedical applications, such as drug and cell delivery, as well as interstitial fluid extraction. Biodegradable hydrogels have also been advantageous for fabricating multi-functional MNs due to their high loading capacity and biocompatibility with the drug of choice. Here, we first review a set of MN devices that can be employed either for biosensing or delivery of multiple target molecules and compare them to the conventional and more simple systems, which are mainly designed for single-molecule sensing or delivery. Subsequently, we expand our insight into advanced MN systems with multiple competencies, such as body fluid extraction, biosensing, and drug delivery at the point of care. The improvement of biomaterials knowledge and biofabrication techniques will allow us to efficiently tune the next generation of smart MNs and provide a realistic platform for more effective personalized therapeutics. This article is protected by copyright. All rights reserved.

MXenes-integrated microneedle combined with asiaticoside to penetrate the cuticle for treatment of diabetic foot ulcer

Patients with diabetic foot ulcers usually suffer from inefficient epithelisation and angiogenesis accompanied by chronic wound healing. Diabetic foot ulcers remain a major challenge in clinical medicine; however, traditional treatments are incapable of transdermal drug delivery, resulting in a low drug delivery rate. We report the development of Ti2C3 MXenes-integrated poly-γ-glutamic acid (γ-PGA) hydrogel microneedles to release asiaticoside (MN-MXenes-AS). Asiaticoside was loaded into PGA-MXenes hydrogel to facilitate cell proliferation while regulating angiogenesis. The characterisation and mechanical strength of the microneedles were investigated in vitro, and the wound-healing efficacy of the microneedles was confirmed in diabetic mice. MXenes significantly improved the mechanical strength of microneedles, while γ-PGA hydrogels provided a moist microenvironment for wound healing. Mice treated with MN-MXenes-AS demonstrated obvious improvements in wound healing process. We successfully fabricated an MXenes-integrated microneedle that possesses sufficient rigidity to penetrate the cuticle for subcutaneous drug delivery, thereby accelerating diabetic wound healing. We demonstrated that MN-MXenes-AS is effective in promoting growth both in vivo and in vitro. Collectively, our data show that MN-MXenes-AS accelerated the healing of diabetic foot ulcers, supporting the use of these microneedles in the treatment of chronic wounds.

Graphical Abstract

Highlights on Advancing Frontiers in Tissue Engineering

The field of tissue engineering continues to advance, sometimes in exponential leaps forward, but also sometimes at a rate that does not fulfill the promise that the field imagined a few decades ago. This review is in part a catalog of success in an effort to inform the process of innovation. Tissue engineering has recruited new technologies and developed new methods for engineering tissue constructs that can be used to mitigate or model disease states for study. Key to this antecedent statement is that the scientific effort must be anchored in the needs of a disease state and be working toward a functional product in regenerative medicine. It is this focus on the wildly important ideas coupled with partnered research efforts within both academia and industry that have shown most translational potential. The field continues to thrive and among the most important recent developments are the use of three-dimensional bioprinting, organ-on-a-chip, and induced pluripotent stem cell technologies that warrant special attention. Developments in the aforementioned areas as well as future directions are highlighted in this article. Although several early efforts have not come to fruition, there are good examples of commercial profitability that merit continued investment in tissue engineering. Impact statement Tissue engineering led to the development of new methods for regenerative medicine and disease models. Among the most important recent developments in tissue engineering are the use of three-dimensional bioprinting, organ-on-a-chip, and induced pluripotent stem cell technologies. These technologies and an understanding of them will have impact on the success of tissue engineering and its translation to regenerative medicine. Continued investment in tissue engineering will yield products and therapeutics, with both commercial importance and simultaneous disease mitigation.

Multifunctional Silica-Modified Hybrid Microgels Templated from Inverse Pickering Emulsions

Microgels are regarded as soft colloids with environmental responsiveness. However, the majority of reported microgels are inherently hydrophilic, resulting in aqueous dispersions, and only used in water-based applications. Herein, we reported an efficient method for hybridization of poly(N-isopropylacrylamide) microgel by coating hydrophobic silica nanoparticles on their surface. The resultant hybrid microgel had switchable surface wettability and could be dispersed in both aqueous and oil phases. Meanwhile, the coated hydrophobic silica nanoparticles solved the difficulty in redispersing microgels caused by particle aggregation and film formation during the drying process, providing a significant advantage in dried storage. Furthermore, the introduction of hydrophobic silica nanoparticles endowed the hybrid microgel with a variety of applications, including cargo encapsulation, active release induced by emulsion reversion, and trace water absorption.

Advances in Nanomedicine Design: Multidisciplinary Strategies for Unmet Medical Needs

Globally, a rising burden of complex diseases takes a heavy toll on human lives and poses substantial clinical and economic challenges. This review covers nanomedicine and nanotechnology-enabled advanced drug delivery systems (DDS) designed to address various unmet medical needs. Key nanomedicine and DDSs, currently employed in the clinic to tackle some of these diseases, are discussed focusing on their versatility in diagnostics, anticancer therapy, and diabetes management. First-hand experiences from our own laboratory and the work of others are presented to provide insights into strategies to design and optimize nanomedicine- and nanotechnology-enabled DDS for enhancing therapeutic outcomes. Computational analysis is also briefly reviewed as a technology for rational design of controlled release DDS. Further explorations of DDS have illuminated the interplay of physiological barriers and their impact on DDS. It is demonstrated how such delivery systems can overcome these barriers for enhanced therapeutic efficacy and how new perspectives of next-generation DDS can be applied clinically.