Glucose Oxidase-Based Glucose-Sensitive Drug Delivery for Diabetes Treatment

Rational design of multifunctional hydrogels targeting the microenvironment of diabetic periodontitis

Periodontitis is a chronic inflammatory disease and is the primary contributor to adult tooth loss. Diabetes exacerbates periodontitis, accelerates periodontal bone resorption. Thus, effectively managing periodontitis in individuals with diabetes is a long-standing challenge. This review introduces the etiology and pathogenesis of periodontitis, and analyzes the bidirectional relationship between diabetes and periodontitis. In this review, we comprehensively summarize the four pathological microenvironments influenced by diabetic periodontitis: high glucose microenvironment, bacterial infection microenvironment, inflammatory microenvironment, and bone loss microenvironment. The hydrogel design strategies and latest research development tailored to the four microenvironments of diabetic periodontitis are mainly focused on. Finally, the challenges and potential solutions in the treatment of diabetic periodontitis are discussed. We believe this review will be helpful for researchers seeking novel avenues in the treatment of diabetic periodontitis.

Improving the stability of insulin through effective chemical modifications: A Comprehensive review

Insulin, an essential peptide hormone, conjointly regulates blood glucose levels by its receptor and it is used as vital drug to treat diabetes. This therapeutic hormone may undergo different chemical modifications during industrial processes, pharmaceutical formulation, and through its endogenous storage in the pancreatic β-cells. Insulin is highly sensitive to environmental stresses and readily undergoes structural changes, being also able to unfold and aggregate in physiological conditions. Even; small changes altering the structural integrity of insulin may have significant impacts on its biological efficacy to its physiological and pharmacological activities. Insulin analogs have been engineered to achieve modified properties, such as improved stability, solubility, and pharmacokinetics, while preserving the molecular pharmacology of insulin. The casually or purposively strategies of chemical modifications of insulin occurred to improve its therapeutic and pharmaceutical properties. Knowing the effects of chemical modification, formation of aggregates, and nanoparticles on protein can be a new look at the production of protein analogues drugs and its application in living system. The project focused on effects of chemical modifications and nanoparticles on the structure, stability, aggregation and their results in effective drug delivery system, biological activity, and pharmacological properties of insulin. The future challenge in biotechnology and pharmacokinetic arises from the complexity of biopharmaceuticals, which are often molecular structures that require formulation and delivery strategies to ensure their efficacy and safety.

Recent advances in transdermal insulin delivery technology: A review

Transdermal drug delivery refers to the administration of drugs through the skin, after which the drugs can directly act on or circulate through the body to the target organs or cells and avoid the first-pass metabolism in the liver and kidneys experienced by oral drugs, reducing the risk of drug poisoning. From the initial singular approach to transdermal drug delivery, there has been a shift toward combining multiple methods to enhance drug permeation efficiency and address the limitations of individual approaches. Technological advancements have also improved the accuracy of drug delivery. Optimizing insulin itself also enables its long-term release via needle-free injectors. In this review, the diverse transdermal delivery methods employed in insulin therapy and their respective advantages and limitations are discussed. By considering factors such as the principles of transdermal penetration, drug delivery efficiency, research progress, synergistic innovations among different methods, patient compliance, skin damage, and posttreatment skin recovery, a comprehensive evaluation is presented, along with prospects for potential novel combinatorial approaches. Furthermore, as insulin is a macromolecular drug, insights gained from its transdermal delivery may also serve as a valuable reference for the use of other macromolecular drugs for treatment.

Layer-by-Layer Nanoparticle Assembly for Biomedicine: Mechanisms, Technologies, and Advancement via Acoustofluidics

The deposition of thin films plays a crucial role in surface engineering, tailoring structural modifications, and functionalization across diverse applications. Layer-by-layer self-assembly, a prominent thin-film deposition method, has witnessed substantial growth since its mid-20th-century inception, driven by the discovery of eligible materials and innovative assembly technologies. Of these materials, micro- and nanoscopic substrates have received far less interest than their macroscopic counterparts; however, this is changing. The catalogue of eligible materials, including nanoparticles, quantum dots, polymers, proteins, cells and liposomes, along with some well-established layer-by-layer technologies, have combined to unlock impactful applications in biomedicine, as well as other areas like food fortification, and water remediation. To access these fields, several well-established technologies have been used, including tangential flow filtration, fluidized bed, atomization, electrophoretic assembly, and dielectrophoresis. Despite the invention of these technologies, the field of particle layer-by-layer still requires further technological development to achieve a high-yield, automatable, and industrially ready process, a requirement for the diverse, reactionary field of biomedicine and high-throughput pharmaceutical industry. This review provides a background on layer-by-layer, focusing on how its constituent building blocks and bonding mechanisms enable unmatched versatility. The discussion then extends to established and recent technologies employed for coating micro- and nanoscopic matter, evaluating their drawbacks and advantages, and highlighting promising areas in microfluidic approaches, where one distinctly auspicious technology emerges, acoustofluidics. The review also explores the potential and demonstrated application of acoustofluidics in layer-by-layer technology, as well as analyzing existing acoustofluidic technologies beyond LbL coating in areas such as cell trapping, cell sorting, and multidimensional particle manipulation. Finally, the review concludes with future perspectives on layer-by-layer nanoparticle coating and the potential impact of integrating acoustofluidic methods.

A multimodal therapy for infected diabetic wounds based on glucose-responsive nanocomposite-integrated microneedles

Diabetic wounds in a state of high glucose are refractory to treatment and healing, especially if they are infected with bacteria. Herein, a novel nanocomposite (CIP/GOx@ZIF-8) was synthesized by loading ciprofloxacin hydrochloride (CIP) and glucose oxidase (GOx) into zeolitic imidazole framework-8 (ZIF-8) that exhibited good glucose sensitivity and catalytic activity. The high glucose in diabetic wounds could be decomposed into hydrogen peroxide (H2O2) and gluconic acid via the catalysis of GOx, which further destroyed CIP/GOx@ZIF-8 to release Zn2+ and cargos. The combination of glucose starvation, Zn2+, H2O2 and CIP could elevate the antibacterial effect and reduce bacterial resistance. Subsequently, the nanocomposite was fabricated into dissolving microneedles (CIP/GOx@ZIF-8 MNs) using polyvinylpyrrolidone (PVP). The microneedles exhibited good mechanical strength, puncture performance, dissolving performance, glucose responsiveness, antibacterial performance and biocompatibility. For in vivo wound healing, CIP/GOx@ZIF-8 MNs with good biosafety facilitated neovascularization and collagen deposition as well as reduced inflammation, and the wounds were almost healed after treatment. This multimodal therapeutic strategy is created to provide a unique treatment for infected diabetic wounds.

Stimuli-Responsive Hydrogels for Protein Delivery

Proteins and peptides are potential therapeutic agents, but their physiochemical properties make their use as drug substances challenging. Hydrogels are hydrophilic polymeric networks that can swell and retain high amounts of water or biological fluids without being dissolved. Due to their biocompatibility, their porous structure, which enables the transport of various peptides and proteins, and their protective effect against degradation, hydrogels have gained prominence as ideal carriers for these molecules' delivery. Particularly, stimuli-responsive hydrogels exhibit physicochemical transitions in response to subtle modifications in the surrounding environment, leading to the controlled release of entrapped proteins or peptides. This review is focused on the application of these hydrogels in protein and peptide delivery, including a brief overview of therapeutic proteins and types of stimuli-responsive polymers.

Recent advances in glucose-oxidase-based nanocomposites for diabetes diagnosis and treatment

Glucose oxidase (GOx) has attracted a lot of attention in the field of diabetes diagnosis and treatment in recent years owing to its inherent biocompatibility and glucose-specific catalysis. GOx can effectively catalyze the oxidation of glucose in the blood to hydrogen peroxide (H2O2) and glucuronic acid and can be used as a sensitive element in biosensors to detect blood glucose concentrations. Nanomaterials based on the immobilization of GOx can significantly improve the performance of glucose sensors through, for example, reduced electron tunneling distance. Moreover, various insulin-loaded nanomaterials (e.g., metal-organic backbones, and mesoporous silica nanoparticles) have been developed for the control of blood glucose concentrations based on GOx catalytic chemistry. These nano-delivery carriers are capable of releasing insulin in response to GOx-mediated changes in the microenvironment, allowing for a rapid return of the blood microenvironment to a normal state. Therefore, glucose biosensors and insulin delivery vehicles immobilized with GOx are important tools for the diagnosis and treatment of diabetes. This paper reviews the characteristics of various GOx-based nanomaterials developed for glucose biosensing and insulin-responsive release as well as research progress, and also highlights the current challenges and opportunities facing this field.

Multiphysics modeling for pressure-thermal sensitive hydrogels

Some smart hydrogels, like poly(N-isopropylacrylamide) (PNIPA) hydrogels, are sensitive to both stimulus hydrostatic pressure and temperature. The model for thermal-sensitive only hydrogels has been well established in the past two decades. In this work, by combining Flory's mean-field theory and Poisson-Nernst-Planck nonlinear equations, we develop a multiphysics model coupling chemo-electro-thermal-mechanical fields which can quantitatively calculate both hydrostatic pressure and thermal sensitivity of hydrogels in an electrolyte bathing solution. Considering PNIPA hydrogels as an example, the proposed model is validated by comparing the numerical results with experimental results reported in the literature. We investigate the influences of initial fixed-charge density, temperature, hydrostatic pressure, and bathing solution concentration on the volume expansion ratio of the hydrogels. Moreover, the concentration of mobile ions and distribution of electric potential within the hydrogel body and bathing solution are quantitatively predicted. The model and results obtained in this paper can be used to better understand the response of smart hydrogels sensitive to both hydrostatic pressure and temperature.

Development of Janus Particles as Potential Drug Delivery Systems for Diabetes Treatment and Antimicrobial Applications

Janus particles have emerged as a novel and smart material that could improve pharmaceutical formulation, drug delivery, and theranostics. Janus particles have two distinct compartments that differ in functionality, physicochemical properties, and morphological characteristics, among other conventional particles. Recently, Janus particles have attracted considerable attention as effective particulate drug delivery systems as they can accommodate two opposing pharmaceutical agents that can be engineered at the molecular level to achieve better target affinity, lower drug dosage to achieve a therapeutic effect, and controlled drug release with improved pharmacokinetics and pharmacodynamics. This article discusses the development of Janus particles for tailored and improved delivery of pharmaceutical agents for diabetes treatment and antimicrobial applications. It provides an account of advances in the synthesis of Janus particles from various materials using different approaches. It appraises Janus particles as a promising particulate system with the potential to improve conventional delivery systems, providing a better loading capacity and targeting specificity whilst promoting multi-drugs loading and single-dose-drug administration.

Partially Oxidized Alginate as a Biodegradable Carrier for Glucose-Responsive Insulin Delivery and Islet Cell Replacement Therapy

Self-regulated insulin delivery that mimics native pancreas function has been a long-term goal for diabetes therapies. Two approaches towards this goal are glucose-responsive insulin delivery and islet cell transplantation therapy. Here, biodegradable, partially oxidized alginate carriers for glucose-responsive nanoparticles or islet cells are developed. Material composition and formulation are tuned in each of these contexts to enable glycemic control in diabetic mice. For injectable, glucose-responsive insulin delivery, 0.5 mm 2.5% oxidized alginate microgels facilitate repeat dosing and consistently provide 10 days of glycemic control. For islet cell transplantation, 1.5 mm capsules comprised of a blend of unoxidized and 2.5% oxidized alginate maintain cell viability and glycemic control over a period of more than 2 months while reducing the volume of nondegradable material implanted. These data show the potential of these biodegradable carriers for controlled drug and cell delivery for the treatment of diabetes with limited material accumulation in the event of multiple doses.

Fabrication Strategies Towards Hydrogels for Biomedical Application: Chemical and Mechanical Insights

This review aims at giving selected chemical and mechanical insights on design criteria that should be taken into account in hydrogel production for biomedical applications. Particular emphasis will be given to the chemical aspects involved in hydrogel design: macromer chemical composition, cross-linking strategies and chemistry towards "conventional" and smart/stimuli responsive hydrogels. Mechanical properties of hydrogels in view of regenerative medicine applications will also be considered.

Review of glucose oxidase as a feed additive: production, engineering, applications, growth-promoting mechanisms, and outlook

The regulation and prohibition of antibiotics used as growth promoters (AGP) in the feed field are increasing because they cause antimicrobial resistance and drug residue issues and threaten community health. Recently, glucose oxidase (GOx) has attracted increasing interest in the feed industry as an alternative to antibiotics. GOx specifically catalyzes the production of gluconic acid (GA) and hydrogen peroxide (H₂O₂) by consuming molecular oxygen, and plays an important role in relieving oxidative stress, preserving health, and promoting animal growth. To expand the application of GOx in the feed field, considerable efforts have been made to mine new genetic resources. Efforts have also been made to heterologously overexpress relevant genes to reduce production costs and to engineer proteins by modifying enzyme properties, both of which are bottleneck problems that limit industrial feed applications. Herein, the: different sources, diverse biochemical properties, distinct structural features, and various strategies of GOx engineering and heterologous overexpression are summarized. The mechanism through which GOx promotes growth in animal production, including the improvement of antioxidant capacity, maintenance of intestinal microbiota homeostasis, and enhancement of gut function, are also systematically addressed. Finally, a new perspective is provided for the future development of GOx applications in the feed field.

Biomedical Applications of polymeric micelles in the treatment of diabetes mellitus: Current success and future approaches

INTRODUCTION

Diabetes mellitus (DM) is the most common metabolic disease and multifactorial, harming patients worldwide. Extensive research has been carried out in the search for novel drug delivery systems offering reliable control of glucose levels for diabetics, aiming at efficient management of DM.

AREAS COVERED

Polymeric micelles (PMs) as smart drug delivery nanocarriers are discussed, focusing on oral drug delivery applications for the management of hyperglycemia. The most recent approaches used for the preparation of smart PMs employ molecular features of amphiphilic block copolymers (ABCs), such as stimulus sensitivity, ligand conjugation, and as a more specific example the ability to inhibit islet amyloidosis.

EXPERT OPINION

PMs provide a unique platform for self-regulated or spatiotemporal drug delivery, mimicking the working mode of pancreatic islets to maintain glucose homeostasis for prolonged periods. This unique characteristic is achieved by tailoring the functional chemistry of ABCs considering the physicochemical traits of PMs, including sensing capabilities, hydrophobicity, etc. In addition, the application of ABCs for the inhibition of conformational changes in islet amyloid polypeptide garnered attention as one of the root causes of DM. However, research in this field is limited and further studies at the clinical level are required.

Advances on Delivery of Cytotoxic Enzymes as Anticancer Agents

Cancer is one of the most serious human diseases, causing millions of deaths worldwide annually, and, therefore, it is one of the most investigated research disciplines. Developing efficient anticancer tools includes studying the effects of different natural enzymes of plant and microbial origin on tumor cells. The development of various smart delivery systems based on enzyme drugs has been conducted for more than two decades. Some of these delivery systems have been developed to the point that they have reached clinical stages, and a few have even found application in selected cancer treatments. Various biological, chemical, and physical approaches have been utilized to enhance their efficiencies by improving their delivery and targeting. In this paper, we review advanced delivery systems for enzyme drugs for use in cancer therapy. Their structure-based functions, mechanisms of action, fused forms with other peptides in terms of targeting and penetration, and other main results from in vivo and clinical studies of these advanced delivery systems are highlighted.

Recent Advances of Stimuli-Responsive Polysaccharide Hydrogels in Delivery Systems: A Review

Hydrogels obtained from natural polymers have received widespread attention for their excellent biocompatible property, nontoxicity, easy gelation, and functionalization. Polysaccharides can regulate the gut microbiota and improve the intestinal microenvironment, thus exerting the healthy effect of intestinal immunity. In an active substance delivery system, the extent and speed of the substance reaching its target are highly dependent on the carrier. Thus, the smart active substance delivery systems are gradually increasing. The smart polysaccharide-hydrogels possess the ability in response to external stimuli through changing their volume phase and structure, which are applied in various fields. Natural polysaccharide-based hydrogels possess excellent characteristics of environmental friendliness, good biocompatibility, and abundant sources. According to the response type, natural polysaccharide-based hydrogels are usually divided into stimulus-responsive hydrogels, including internal response (pH, temperature, enzyme, redox) and external response (light, electricity, magnetism) hydrogels. The delivery system based on polysaccharides can exert their effects in the gastrointestinal tract. At the same time, polysaccharides may also take part in regulating the brain signals through the microbiota-gut-brain axis. Therefore, natural polysaccharide-hydrogels are considered as promising biomaterials, which can be designed as delivery systems for regulating the gut-brain axis. This article reviews the research advance of stimulus-responsive hydrogels, which focus on the types, response characteristics, and applications for polysaccharide-based smart hydrogels as delivery systems.

Glucose-sensitive delivery of tannic acid by a photo-crosslinked chitosan hydrogel film for antibacterial and anti-inflammatory therapy

A glucose-sensitive antibacterial and anti-inflammatory hydrogel film with controlled release of tannic acid (TA) was synthesized using chitosan (CS). Specifically, the photo-crosslinked CS hydrogel was first obtained and then immersed in TA solution to generate composite hydrogel film with enhanced mechanical properties. Subsequently, N-hydroxysuccinimide/1-ethyl-3-(3-dimethylaminopropyl) carbodiimide based coupling chemistry was used to covalently crosslink glucose oxidase (GOx) to CS to obtain glucose sensitivity. The physicochemical properties, including chemical composition, enzyme-related characteristics, glucose responsiveness, and mechanical strength, were thoroughly investigated, followed by the cytotoxicity, antibacterial and anti-inflammatory tests. The results showed that the GOx immobilized on the film surface by covalent bonding gave better stability than those that were physically adsorbed. In addition, it could quickly and correspondingly modify its inner pore structure in response to the glucose stimulus and then control the loaded TA release. Meanwhile, the TA addition could enhance the film's mechanical properties. The composite hydrogel film demonstrated adequate biocompatibility and can inhibit NO, IL-6, and TNF-α production in stimulated macrophages, as well as Porphyromonas gingivalis growth, demonstrating effective antibacterial and anti-inflammatory activity.

Glucose and H2O2 Dual-Responsive Nanocomplex Grafted with Insulin Prodrug for Blood Glucose Regulation

Although "closed-loop" smart insulin delivery systems have been extensively investigated, the majority of them suffer from low insulin loading efficiency and slow glucose response. Here, we constructed a novel nanocomplex (NC), which was prepared by electrostatic interaction between negatively charged insulin prodrug nanoparticles (NPs) and positively charged polycaprolactone-polyethylenimine (PCL-PEI) micelles. The insulin prodrug was linked to acetalated dextran (AD) via borate ester bonds to form IAD NPs, and glucose oxidase (GOx) was encapsulated in PCL-PEI micelles. The NC was negatively charged with a high insulin grafting rate (0.473 mg/mg), and in vitro experiments revealed that IAD was sensitive to hyperglycemia and H₂O₂, whereas GOx significantly improved the response to glucose by altering the microenvironment to promote sustained insulin release. Furthermore, compared with free insulin and IAD NPs, subcutaneously injected NCs in diabetic rats had long-term hypoglycemic effects, showing excellent biocompatibility in vitro and in vivo, which had good potential in insulin self-regulation delivery.

Nanofibrous Membrane with Encapsulated Glucose Oxidase for Self-Sustained Antimicrobial Applications

Polyvinyl alcohol (PVA) nanofibrous membrane, consisting of separately encapsulated glucose oxidase (GOx) and glucose (Glu) nanofibers, was prepared via simultaneously electrospinning PVA/GOx and PVA/Glu dopes. The as-prepared pristine membrane could self-sustainably generate hydrogen peroxide (H2O2) only in contact with an aqueous solution. The H2O2 production level was well maintained even after storing the dry membrane at room temperature for 7 days. Cross-linking the membrane via reaction with glutaraldehyde (GA) vapor could not only prevent the nanofibrous membrane from dissolving in water but also prolonged the release of H2O2. The sustained release of H2O2 from the membrane achieved antimicrobial capability equivalent to that of 1% H2O2 against both Escherichia coli and Staphylococcus aureus. Gram(+) S. aureus cells were more susceptible to H2O2 than Gram(-) E. coli and >99% of S. aureus were killed after 1 h incubation with the membrane. Pristine and GA-crosslinked nanofibrous membrane with in situ production of H2O2 were self-sterilized in which no microorganism contamination on the membrane could be detected after 2 weeks incubation on an agar plate. The GOx/Glu membrane may find potential application as versatile antimicrobial materials in the field of biomedicine, in the food and health industries, and especially challenges related to wound healing in diabetic patients.

Tuneable Time Delay in the Burst Release from Oxidation-Sensitive Polymersomes Made by PISA

Reactive polymersomes represent a versatile artificial cargo carrier system that can facilitate an immediate release in response to a specific stimulus. The herein presented oxidation-sensitive polymersomes feature a time-delayed release mechanism in an oxidative environment, which can be precisely adjusted by either tuning the membrane thickness or partial pre-oxidation. These polymeric vesicles are conveniently prepared by PISA allowing the straightforward and effective in situ encapsulation of cargo molecules, as shown for dyes and enzymes. Kinetic studies revealed a critical degree of oxidation causing the destabilization of the membrane, while no release of the cargo is observed beforehand. The encapsulation of glucose oxidase directly transforms these polymersomes into glucose-sensitive vesicles, as small molecules including sugars can passively penetrate their membrane. Considering the ease of preparation, these polymersomes represent a versatile platform for the confinement and burst release of cargo molecules after a precisely adjustable time span in the presence of specific triggers, such as H2 O2 or glucose.

Enzyme-polymeric/inorganic metal oxide/hybrid nanoparticle bio-conjugates in the development of therapeutic and biosensing platforms

Background

Because enzymes can control several metabolic pathways and regulate the production of free radicals, their simultaneous use with nanoplatforms showing protective and combinational properties is of great interest in the development of therapeutic nano-based platforms. However, enzyme immobilization on nanomaterials is not straightforward due to the toxic and unpredictable properties of nanoparticles in medical practice.

Aim of review

In fact, because of the ability to load enzymes on nano-based supports and increase their renewability, scientific groups have been tempted to create potential therapeutic enzymes in this field. Therefore, this study not only pays attention to the therapeutic and diagnostic applications of diseases by enzyme-nanoparticle (NP) bio-conjugate (abbreviated as: ENB), but also considers the importance of nanoplatforms used based on their toxicity, ease of application and lack of significant adverse effects on loaded enzymes. In the following, based on the published reports, we explained that the immobilization of enzymes on polymers, inorganic metal oxide and hybrid compounds provide hopes for potential use of ENBs in medical activities. Then, the use of ENBs in bioassay activities such as paper-based or wearing biosensors and lab-on-chip/microfluidic biosensors were evaluated. Finally, this review addresses the current challenges and future perspective of ENBs in biomedical applications.

Key scientific concepts of review

This literature may provide useful information regarding the application of ENBs in biosensing and therapeutic platforms.

Raising the 'Good' Oxidants for Immune Protection

Redox medicine is a new therapeutic concept targeting reactive oxygen species (ROS) and secondary reaction products for health benefit. The concomitant function of ROS as intracellular second messengers and extracellular mediators governing physiological redox signaling, and as damaging radicals instigating or perpetuating various pathophysiological conditions will require selective strategies for therapeutic intervention. In addition, the reactivity and quantity of the oxidant species generated, its source and cellular location in a defined disease context need to be considered to achieve the desired outcome. In inflammatory diseases associated with oxidative damage and tissue injury, ROS source specific inhibitors may provide more benefit than generalized removal of ROS. Contemporary approaches in immunity will also include the preservation or even elevation of certain oxygen metabolites to restore or improve ROS driven physiological functions including more effective redox signaling and cell-microenvironment communication, and to induce mucosal barrier integrity, eubiosis and repair processes. Increasing oxidants by host-directed immunomodulation or by exogenous supplementation seems especially promising for improving host defense. Here, we summarize examples of beneficial ROS in immune homeostasis, infection, and acute inflammatory disease, and address emerging therapeutic strategies for ROS augmentation to induce and strengthen protective host immunity.

Intelligent Nanoparticle-Based Dressings for Bacterial Wound Infections

Conventional wound dressing materials containing free antibiotics for bacterial wound infections are presented with several limitations, that is, lack of controlled and triggered release capabilities, and may often not be adequate to address the complex bacteria microenvironment of such infections. Additionally, the improper usage of antibiotics may also result in the emergence of drug resistant strains. While delivery systems (i.e., nanoparticles) that encapsulate antibiotics may potentially overcome some of these limitations, their therapeutic outcomes are still less than desirable. For example, premature drug release or unintended drug activation may occur, which would greatly reduce treatment efficacy. To address this, responsive nanoparticle-based antimicrobial therapies could be a promising strategy. Such nanoparticles can be functionalized to react to a single stimulus or multi stimulus within the bacteria microenvironment and subsequently elicit a therapeutic response. Such "intelligent" nanoparticles can be designed to respond to the microenvironment, that is, an acidic pH, the presence of specific enzymes, bacterial toxins, etc. or to an external stimulus, for example, light, thermal, etc. These responsive nanoparticles can be further incorporated into wound dressings to better promote wound healing. This review summarizes and highlights the recent progress on such intelligent nanoparticle-based dressings as potential wound dressings for bacteria-infected wounds, along with the current challenges and prospects for these technologies to be successfully translated into the clinic.

Stimuli-responsive mesoporous silica nanoparticles: A custom-tailored next generation approach in cargo delivery

The pre-mature release of therapeutic cargos in the bloodstream or off-target sites is a major hurdle in drug delivery. However, stimuli-specific drug release responses are capable of providing greater control over the cargo release. Herein, various types of nanocarriers have been employed for such applications. Among various types of nanoparticles, mesoporous silica nanoparticles (MSNPs) have several attractive characteristics, such as high loading capacity, biocompatibility, small size, porous structure, high surface area, tunable pore size and ease of functionalization of the external and internal surfaces, which facilitates the entrapment and development of stimuli-dependent release of drugs. MSNPs could be modified with such stimuli-responsive entities like nucleic acid, peptides, polymers, organic molecules, etc., to prevent pre-mature cargo release, improving the therapeutic outcome. This controlled drug release system could be modulated to function upon extracellular or intracellular specific stimuli, including pH, enzyme, glucose, glutathione, light, temperature, etc., and thus provide minimal side effects at non-target sites. This system has great potential applications for the targeted delivery of therapeutics to treat clinically challenging diseases like cancer. This review summarizes the synthesis and design of stimuli-responsive release strategies of MSNP-based drug delivery systems along with investigations in biomedical applications.

Glucose oxidase: Applications, sources, and recombinant production

Glucose oxidase is a subset of oxidoreductase enzymes that catalyzes the transfer of electrons from an oxidant to a reductant. Glucose oxidases use oxygen as an external electron acceptor that releases hydrogen peroxide (H₂ O₂ ). Glucose oxidase has many applications in commercial processes, including improving the color and taste, increasing the persistence of food materials, removing the glucose from the dried egg, and eliminating the oxygen from different juices and beverages. Moreover, glucose oxidase, along with catalase, is used in glucose testing kits (especially in biosensors) to detect and measure the presence of glucose in industrial and biological solutions (e.g., blood and urine specimens). Hence, glucose oxidase is a valuable enzyme in the industry and medical diagnostics. Therefore, evaluating the structure and function of glucose oxidase is crucial for modifying as well as improving its catalytic properties. Finding different sources of glucose oxidase is an effective way to find the type of enzyme with the desired catalysis. Besides, the recombinant production of glucose oxidase is the best approach to produce sufficient amounts of glucose oxidase for various uses. Accordingly, the study of various aspects of glucose oxidase in biotechnology and bioprocessing is crucial.

Chemically-Gated and Sustained Molecular Transport through Nanoporous Gold Thin Films in Biofouling Conditions

Sustained release and replenishment of the drug depot are essential for the long-term functionality of implantable drug-delivery devices. This study demonstrates the use nanoporous gold (np-Au) thin films for in-plane transport of fluorescein (a small-molecule drug surrogate) over large (mm-scale) distances from a distal reservoir to the site of delivery, thereby establishing a constant flux of molecular release. In the absence of halides, the fluorescein transport is negligible due to a strong non-specific interaction of fluorescein with the pore walls. However, in the presence of physiologically relevant concentration of ions, halides preferentially adsorb onto the gold surface, minimizing the fluorescein–gold interactions and thus enabling in-plane fluorescein transport. In addition, the nanoporous film serves as an intrinsic size-exclusion matrix and allows for sustained release in biofouling conditions (dilute serum). The molecular release is reproducibly controlled by gating it in response to the presence of halides at the reservoir (source) and the release site (sink) without external triggers (e.g., electrical and mechanical).

Microgel encapsulated nanoparticles for glucose-responsive insulin delivery

An insulin delivery system that self-regulates blood glucose levels has the potential to limit hypoglycemic events and improve glycemic control. Glucose-responsive insulin delivery systems have been developed by coupling glucose oxidase with a stimuli-responsive biomaterial. However, the challenge of achieving desirable release kinetics (i.e., insulin release within minutes after glucose elevation and duration of release on the order of weeks) still remains. Here, we develop a glucose-responsive delivery system using encapsulated glucose-responsive, acetalated-dextran nanoparticles in porous alginate microgels. The nanoparticles respond rapidly to changes in glucose concentrations while the microgels provide them with protection and stability, allowing for extended glucose-responsive insulin release. This system reduces blood sugar in a diabetic mouse model at a rate similar to naked insulin and responds to a glucose challenge 3 days after administration similarly to a healthy animal. With 2 doses of microgels containing 60 IU/kg insulin each, we are able to achieve extended glycemic control in diabetic mice for 22 days.

Honey-inspired antimicrobial hydrogels resist bacterial colonization through twin synergistic mechanisms

Inspired by the interesting natural antimicrobial properties of honey, biohybrid composite materials containing a low-fouling polymer hydrogel network and an encapsulated antimicrobial peroxide-producing enzyme have been developed. These synergistically combine both passive and active mechanisms for reducing microbial bacterial colonization. The mechanical properties of these materials were assessed using compressive mechanical analysis, which revealed these hydrogels possessed tunable mechanical properties with Young's moduli ranging from 5 to 500 kPa. The long-term enzymatic activities of these materials were also assessed over a 1-month period using colorimetric assays. Finally, the passive low-fouling properties and active antimicrobial activity against a leading opportunistic pathogen, Staphylococcus epidermidis, were confirmed using bacterial cell counting and bacterial adhesion assays. This study resulted in non-adhesive substrate-permeable antimicrobial materials, which could reduce the viability of planktonic bacteria by greater than 7 logs. It is envisaged these new biohybrid materials will be important for reducing bacterial adherence in a range of industrial applications.

Emerging Nano- and Micro-Technologies Used in the Treatment of Type-1 Diabetes

Type-1 diabetes is characterized by high blood glucose levels due to a failure of insulin secretion from beta cells within pancreatic islets. Current treatment strategies consist of multiple, daily injections of insulin or transplantation of either the whole pancreas or isolated pancreatic islets. While there are different forms of insulin with tunable pharmacokinetics (fast, intermediate, and long-acting), improper dosing continues to be a major limitation often leading to complications resulting from hyper- or hypo-glycemia. Glucose-responsive insulin delivery systems, consisting of a glucose sensor connected to an insulin infusion pump, have improved dosing but they still suffer from inaccurate feedback, biofouling and poor patient compliance. Islet transplantation is a promising strategy but requires multiple donors per patient and post-transplantation islet survival is impaired by inflammation and suboptimal revascularization. This review discusses how nano- and micro-technologies, as well as tissue engineering approaches, can overcome many of these challenges and help contribute to an artificial pancreas-like system.

Fabrication and characterization of a novel semi-interpenetrating network hydrogel based on sodium carboxymethyl cellulose and poly(methacrylic acid) for oral insulin delivery

In this research, pH-sensitive semi-interpenetrating polymer network hydrogels based on sodium carboxymethyl cellulose and poly(methacrylic acid) were synthesized using free radical polymerization and semi-interpenetrating polymer network approach for oral administration of insulin. The chemical structure and thermal stability of the hydrogels were characterized using Fourier transform infrared spectroscopy, X-ray diffraction, and thermogravimetric analysis measurements. The interior morphology was observed by scanning electron microscopy and the inner structure exhibited a porous honeycomb-like shape. The investigations on the swelling properties of hydrogels revealed their ability to response to pH value change. The in vitro release behavior of insulin was pH dependent and the release of insulin was much lower at pH 1.2 compared to pH 6.8. In vitro cytotoxicity assay indicated that the hydrogels were noncytotoxic to HeLa cells. A sustained reduction in blood glucose level was observed after oral administration of insulin-loaded hydrogel to diabetic rats at 75 IU/kg. These results indicated that the hydrogel would be a promising vehicle for oral insulin delivery systems.

Synthesis and Applications of Hydrogels in Cancer Therapy

Hydrogels are water-insoluble, hydrophilic, cross-linked, three-dimensional networks of polymer chains having the ability to swell and absorb water but do not dissolve in it, that comprise the major difference between gels and hydrogels. The mechanical strength, physical integrity and solubility are offered by the crosslinks. The different applications of hydrogels can be derived based on the methods of their synthesis, response to different stimuli, and their different kinds. Hydrogels are highly biocompatible and have properties similar to human tissues that make it suitable to be used in various biomedical applications, including drug delivery and tissue engineering. The role of hydrogels in cancer therapy is highly emerging in recent years. In the present review, we highlighted different methods of synthesis of hydrogels and their classification based on different parameters. Distinctive applications of hydrogels in the treatment of cancer are also discussed.

Polymer-Based Nanoparticle Strategies for Insulin Delivery

Diabetes mellitus (DM) is a chronic metabolic illness estimated to have affected 451 million individuals to date, with this number expected to significantly rise in the coming years. There are two main classes of this disease, namely type 1 diabetes (T1D) and type 2 diabetes (T2D). Insulin therapy is pivotal in the management of diabetes, with diabetic individuals taking multiple daily insulin injections. However, the mode of administration has numerous drawbacks, resulting in poor patient compliance. In order to optimize insulin therapy, novel drug delivery systems (DDSes) have been suggested, and alternative routes of administration have been investigated. A novel aspect in the field of drug delivery was brought about by the coalescence of polymeric science and nanotechnology. In addition to polymeric nanoparticles (PNPs), insulin DDSes can incorporate the use of nanoplatforms/carriers. A combination of these systems can bring about novel formulations and lead to significant improvements in the drug delivery system (DDS) with regard to therapeutic efficacy, bioavailability, increased half-life, improved transport through physical and chemical barriers, and controlled drug delivery. This review will discuss how recent developments in polymer chemistry and nanotechnology have been employed in a multitude of platforms as well as in administration routes for the safe and efficient delivery of insulin for the treatment of DM.

Synthesized of glucose-responsive nanogels labeled with fluorescence molecule based on phenylboronic acid by RAFT polymerization

We reported on the fabrication of sugar-responsive nanogels covalently incorporated with 3-acrylamidophenylboronic acid (AAPBA) as glucose-recognizing moiety, 2-(acrylamido)glucopyranose (AGA) as biocompatible moiety, and boron dipyrromethene (BODIPYMA) as fluorescence donor molecule. The p(AAPBA-AGA-BODIPYMA) nanogels were synthesized via reversible addition-fragmentation chain transfer (RAFT) polymerization in the mixture solvents of H₂O/ethanol. Nanogels could respond to glucose and size of nanogels increased after treating with 3 mg/mL glucose medium. The fluorescent intensity of nanogels varied dependent on different glucose concentrations. Besides, insulin, a model drug, can be encapsulated into nanogels with the loading amount up to 8.2%. The drug release was dependent on the content of AAPBA moieties in nanogels and glucose concentrations in release medium. The investigation on the cytotoxicity of nanogels revealed that nanogels had good compatibility. Such glucose-responsive nanogels have potential in detection and treatment of diabetes.

Design strategies for chemical-stimuli-responsive programmable nanotherapeutics

Chemical-stimuli-responsive nanotherapeutics have gained great interest in drug delivery and diagnosis applications. These nanotherapeutics are designed to respond to specific internal stimuli including pH, ionic strength, redox, reactive oxygen species, glucose, enzymes, ATP and hypoxia for site-specific and responsive or triggered release of payloads and/or biomarker detections. This review systematically and comprehensively addresses up-to-date technological and design strategies, and challenges nanomaterials to be used for triggered release and sensing in response to chemical stimuli.

Novel and green synthesis of a nanopolymer and its use as a drug delivery system of silibinin and silymarin extracts in the olfactory ensheathing cells of rats in normal and high-glucose conditions

Drug delivery systems have been of interest to researchers. The effects of synthesized nano-polymers as silibinin and silymarin extract drug delivery systems on olfactory ensheathing cells under normal and high-glucose conditions were studied. The structure of the nanopolymer was characterized by IR, HNMR, GPC, DLS, and AFM. The toxicity was evaluated by an MTT assay. The production of ROS and the generation of NO were evaluated by a probe of fluorescein diacetate and Griess methods, respectively. The expressions of the protein levels of ILK, VEGF, BDNF, and NGF were investigated by western blotting. The polymer size was between 50 and 150 nm. The loading capacities for silibinin and silymarin were 68.5% and 56.4%, respectively, and the drug release for them was estimated at 54.1% and 50.8%, respectively. In high-glucose conditions, the cells were protected (EC₅₀ = 4.88 ± 0.5 μM) by silibinin and nanopolymer in low concentrations by reducing the amount of ROS and NO, maintaining ILK, reducing VEGF and increasing NGF and BDNF. Incubation with silibinin and nanopolymer at high concentrations increased cell death with LC₅₀ = 57.36 ± 2.5 and 43.18 ± 1.8 μM, respectively, in high-glucose states. Thus, the cells were protected by silibinin and nanopolymer in protective concentrations by reducing the amount of ROS and NO, maintaining ILK, reducing VEGF, and increasing BDNF and NGF. The mentioned mechanisms were totally reversed at high concentrations.

A schematic of a new synthesized nanopolymer (CGONP) and its use as a drug delivery system of silibinin and silymarin extract in the olfactory ensheathing cells (OECs) of rats in normal and high-glucose conditions.

Advanced electronic skin devices for healthcare applications

Electronic skin, a kind of flexible electronic device and system inspired by human skin, has emerged as a promising candidate for wearable personal healthcare applications. Wearable electronic devices with skin-like properties will provide platforms for continuous and real-time monitoring of human physiological signals such as tissue pressure, body motion, temperature, metabolites, electrolyte balance, and disease-related biomarkers. Transdermal drug delivery devices can also be integrated into electronic skin to enhance its non-invasive, real-time dynamic therapy functions. This review summarizes the recent progress in electronic skin devices for applications in human health monitoring and therapy systems as well as several potential mass production technologies such as inkjet printing and 3D printing. The opportunities and challenges in broadening the applications of electronic skin devices in practical healthcare are also discussed.

Porous Cellulose Nanofiber-Based Microcapsules for Biomolecular Sensing

Cellulose nanofibers (CNFs) have recently attracted a lot of attention in sensing because of their multifunctional character and properties such as renewability, nontoxicity, biodegradability, printability, and optical transparency in addition to unique physicochemical, barrier, and mechanical properties. However, the focus has exclusively been devoted toward developing two-dimensional sensing platforms in the form of nanopaper or nanocellulose-based hydrogels. To improve the flexibility and sensing performance in situ, for example, to detect biomarkers in vivo for early disease diagnostics, more advanced CNF-based structures are needed. Here, we developed porous and hollow, yet robust, CNF-based microcapsules using only the primary plant cell wall components, CNF, pectin, and xyloglucan, to assemble the capsule wall. The fluorescein isothiocyanate-labeled dextrans with M_W of 70 and 2000 kDa could enter the hollow capsules at a rate of 0.13 ± 0.04 and 0.014 ± 0.009 s^-1, respectively. This property is very attractive because it minimizes the influence of mass transport through the capsule wall on the response time. As a proof of concept, glucose oxidase (GOx) enzyme was loaded (and cross-linked) in the microcapsule interior with an encapsulation efficiency of 68 ± 2%. The GOx-loaded microcapsules were immobilized on a variety of surfaces (here, inside a flow channel, on a carbon-coated sensor or a graphite rod) and glucose concentrations up to 10 mM could successfully be measured. The present concept offers new opportunities in the development of simple, more efficient, and disposable nanocellulose-based analytical devices for several sensing applications including environmental monitoring, healthcare, and diagnostics.

Preparation of Nafion/Polycation Layer-by-Layer Films for Adsorption and Release of Insulin

Thin films were prepared using layer-by-layer (LbL) deposition of Nafion (NAF) and polycations such as poly(allylamine hydrochloride) (PAH), poly(ethyleneimine) (PEI), and poly(diallydimethylammonium chloride) (PDDA). Insulin was then adsorbed on the NAF-polycation LbL films by immersion in an insulin solution. The NAF-polycation LbL films were characterized using a quartz crystal microbalance and an atomic force microscope. The release of insulin from the LbL films was characterized using UV-visible adsorption spectroscopy and fluorescence emission spectroscopy. The greatest amount of insulin was adsorbed on the NAF-PAH LbL film. The amount of insulin adsorbed on the (NAF/PAH)₅NAF LbL films by immersion in a 1 mg mL-1 insulin solution at pH 7.4 was 61.8 µg cm-2. The amount of insulin released from the LbL films was higher when immersed in insulin solutions at pH 2.0 and pH 9.0 than at pH 7.4. Therefore, NAF-polycations could be employed as insulin delivery LbL films under mild conditions and as an insulin release control system according to pH change.

A Novel Glucose Biosensor Based on Hierarchically Porous Block Copolymer Film

Enzymatic biosensors are widely used in clinical diagnostics, and electrode materials are essential for both the efficient immobilization of enzyme and the fast electron transfer between the active sites of enzyme and electrode surface. Electrode materials with a hierarchically porous structure can not only increase the specific surface area but also promote the electron transfer, facilitating the catalysis reaction. Block copolymer is a good candidate for preparation of film with a hierarchically porous structure due to its unique characteristics of self-assembly and phase separation. In the current work, hierarchically porous block copolymer film containing both micropores and nanopores was prepared by spinodal decomposition induced phase separation. The resultant copolymer film was adopted as the electrode material to immobilize glucose oxidase (GOx) for construction of an enzyme biosensor. Scanning electron microscopy (SEM), contact angle (CA) measurements, and Fourier-transform infrared (FTIR) and electrochemical impendence spectroscopy (EIS) were adopted to investigate the microstructure of the as-developed biosensor. Results demonstrated that the hierarchically porous block copolymer film offered a favorable and biocompatible microenvironment for proteins. These as-prepared glucose biosensors possessed a wide linear range (10⁻4500 μM), a low detection limit (0.05 μM), quick response (2 s), excellent stability, and selectivity. This work demonstrates that hierarchically porous block copolymer film is a good matrix candidate for the immobilization of the enzyme and provides a potential electrode material to construct novel biosensors with excellent performance.

Glucose- and H2O2-Responsive Polymeric Vesicles Integrated with Microneedle Patches for Glucose-Sensitive Transcutaneous Delivery of Insulin in Diabetic Rats

Herein, a dual-responsive insulin delivery device by integrating glucose- and H₂O₂-responsive polymeric vesicles (PVs) with transcutaneous microneedles (MNs) has been designed. This novel microneedle delivery device achieves a goal of fast response, excellent biocompatibility, and painless administration. The PVs are self-assembled from a triblock copolymer including poly(ethylene glycol), poly(phenylboronic acid) (glucose-sensitive block), and poly(phenylboronic acid pinacol ester) (H₂O₂-sensitive block). After loading with insulin and glucose oxidase (GO _x), the drug-loaded PVs display a basal insulin release as well as a promoted insulin release in response to hyperglycemic states. The insulin release rate responds quickly to elevated glucose and can be further promoted by the incorporated GO _x, which will generate the H₂O₂ at high glucose levels and further break the chemical links of phenylboronic acid pinacol ester group. Finally, the transdermal delivery of insulin to the diabetic rats ((insulin + GO _x)-loaded MNs) presents an effective hypoglycemic effect compared to that of subcutaneous injection or only insulin-loaded MNs, which indicates the as-prepared MNs insulin delivery system could be of great importance for the applications in the therapy of diabetes.

BioMEMS for biosensors and closed-loop drug delivery

The efficacy of pharmaceutical treatments can be greatly enhanced by physiological feedback from the patient using biosensors, though this is often invasive or infeasible. By adapting microelectromechanical systems (MEMS) technology to miniaturize such biosensors, previously inaccessible signals can be obtained, often from inside the patient. This is enabled by the device's extremely small footprint which minimizes both power consumption and implantation trauma, as well as the transport time for chemical analytes, in turn decreasing the sensor's response time. MEMS fabrication also allows mass production which can be easily scaled without sacrificing its high reproducibility and reliability, and allows seamless integration with control circuitry and telemetry which is already produced using the same materials and fabrication steps. By integrating these systems with drug delivery devices, many of which are also MEMS-based, closed loop drug delivery can be achieved. This paper surveys the types of signal transduction devices available for biosensing-primarily electrochemical, optical, and mechanical-looking at their implementation via MEMS technology. The impact of MEMS technology on the challenges of biosensor development, particularly safety, power consumption, degradation, fouling, and foreign body response, are also discussed.