Transfer-molded wrappable microneedle meshes for perivascular drug delivery

Diagnostic, Therapeutic, and Theranostic Multifunctional Microneedles

Microneedles (MNs) have maintained their popularity in therapeutic and diagnostic medical applications throughout the past decade. MNs are originally designed to gently puncture the stratum corneum layer of the skin and have lately evolved into intelligent devices with functions including bodily fluid extraction, biosensing, and drug administration. MNs offer limited invasiveness, ease of application, and minimal discomfort. Initially manufactured solely from metals, MNs are now available in polymer-based varieties. MNs can be used to create systems that deliver drugs and chemicals uniformly, collect bodily fluids, and are stimulus-sensitive. Although these advancements are favorable in terms of biocompatibility and production costs, they are insufficient for the therapeutic use of MNs. This is the first comprehensive review that discusses individual MN functions toward the evolution and development of smart and multifunctional MNs for a variety of novel and impactful future applications. The study examines fabrication techniques, application purposes, and experimental details of MN constructs that perform multiple functions concurrently, including sensing, drug-molecule release, sampling, and remote communication capabilities. It is highly likely that in the near future, MN-based smart devices will be a useful and important component of standard medical practice for different applications.

Periadventitial biomaterials to improve arteriovenous fistula and graft outcomes

Periadventitial biomaterials have been employed for nearly three decades to promote adaptive venous remodeling following hemodialysis vascular access creation in preclinical models and clinical trials. These systems are predicated on the combination of scaffolds, hydrogels, and/or particles with therapeutics (small molecules, proteins, genes, and cells) to prevent venous stenosis and subsequent maturation failure. Periadventitial biomaterial therapies have evolved from simple drug delivery vehicles for traditional drugs to more thoughtful designs tailored to the pathophysiology of access failure. The emergence of tissue engineering strategies and gene therapies are another exciting new direction. Despite favorable results in experimental and preclinical studies, no periadventitial therapy has been clinically approved to improve vascular access outcomes. After conducting an exhaustive review of the literature, we identify the seminal studies and clinical trials that utilize periadventitial biomaterials and discuss the key features of each biomaterial format and their respective shortcomings as they pertain to access maturation. This review provides a foundation from which clinicians, surgeons, biologists, and engineers can refer to and will hopefully inspire thoughtful, translatable treatments to finally address access failure.

Applications and prospects of microneedles in tumor drug delivery

As drug delivery devices, microneedles are used widely in the local administration of various drugs. Such drug-loaded microneedles are minimally invasive, almost painless, and have high drug delivery efficiency. In recent decades, with advancements in microneedle technology, an increasing number of adaptive, engineered, and intelligent microneedles have been designed to meet increasing clinical needs. This article summarizes the types, preparation materials, and preparation methods of microneedles, as well as the latest research progress in the application of microneedles in tumor drug delivery. This article also discusses the current challenges and improvement strategies in the use of microneedles for tumor drug delivery.

Effect of sequential release of sirolimus and rosuvastatin using silk fibroin microneedle to prevent intimal hyperplasia

Intimal hyperplasia (IH) is a major cause of vascular restenosis after bypass surgery, which progresses as a series of processes from the acute to chronic stage in response to endothelial damage during bypass grafting. A strategic localized drug delivery system that reflects the pathophysiology of IH and minimizes systemic side effects is necessary. In this study, the sequential release of sirolimus, a mechanistic target of rapamycin (mTOR) inhibitor, and statin, an HMG-COA inhibitor, was realized as a silk fibroin-based microneedle device in vivo. The released sirolimus in the acute stage reduced neointima (NI) and vascular fibrosis through mTOR inhibition. Furthermore, rosuvastatin, which was continuously released from the acute to chronic stage, reduced vascular stiffness and apoptosis through the inactivation of Yes-associated protein (YAP). The sequential release of sirolimus and rosuvastatin confirmed the synergistic treatment effects on vascular inflammation, VSMC proliferation, and ECM degradation remodeling through the inhibition of transforming growth factor (TGF)-beta/NF-κB pathway. These results demonstrate the therapeutic effect on preventing restenosis with sufficient vascular elasticity and significantly reduced IH in response to endothelial damage. Therefore, this study suggests a promising strategy for treating coronary artery disease through localized drug delivery of customized drug combinations.

Going below and beyond the surface: Microneedle structure, materials, drugs, fabrication, and applications for wound healing and tissue regeneration

Microneedle, as a novel drug delivery system, has attracted widespread attention due to its non-invasiveness, painless and simple administration, controllable drug delivery, and diverse cargo loading capacity. Although microneedles are initially designed to penetrate stratum corneum of skin for transdermal drug delivery, they, recently, have been used to promote wound healing and regeneration of diverse tissues and organs and the results are promising. Despite there are reviews about microneedles, few of them focus on wound healing and tissue regeneration. Here, we review the recent advances of microneedles in this field. We first give an overview of microneedle system in terms of its potential cargos (e.g., small molecules, macromolecules, nucleic acids, nanoparticles, extracellular vesicle, cells), structural designs (e.g., multidrug structures, adhesive structures), material selection, and drug release mechanisms. Then we briefly summarize different microneedle fabrication methods, including their advantages and limitations. We finally summarize the recent progress of microneedle-assisted wound healing and tissue regeneration (e.g., skin, cardiac, bone, tendon, ocular, vascular, oral, hair, spinal cord, and uterine tissues). We expect that our article would serve as a guideline for readers to design their microneedle systems according to different applications, including material selection, drug selection, and structure design, for achieving better healing and regeneration efficacy.

Balloon Catheter-Integrated Piezoelectric Micropyramid Arrays for Measuring Vascular Stiffness

Atherosclerosis is one of the severe cardiovascular diseases in which blood vessels lose elasticity and the lumen narrows. If atherosclerosis worsens, it commonly leads to acute coronary syndrome (ACS) due to the rupture of vulnerable plaque or aortic aneurysm. As the mechanical properties of vascular tissues vary from their conditions, measuring the vascular stiffness of an inner blood vessel wall may be applied to the accurate diagnosis of atherosclerotic symptoms. Therefore, early mechanical detection of vascular stiffness is highly needed for immediate medical attention for ACS. Even with conventional examination methods such as intravascular ultrasonography and optical coherence tomography, several limitations still remain that make it difficult to directly determine the mechanical properties of the vascular tissue. As piezoelectric materials convert mechanical energy to electricity without an external power source, a piezoelectric nanocomposite could be utilized as a balloon catheter-integrated mechanical sensor on its surface. Here, we present piezoelectric nanocomposite micropyramid balloon catheter (p-MPB) arrays for measuring vascular stiffness. We study the structural characterization and feasibility of p-MPB as endovascular sensors by conducting finite element method analyses. Also, multifaceted piezoelectric voltages are measured by compression/release tests, in vitro vascular phantom tests, and ex vivo porcine heart tests to confirm that the p-MPB sensor properly operates in blood vessels.

Microneedles for in situ tissue regeneration

Tissue injury is a common clinical problem, which may cause great burden on patients' life. It is important to develop functional scaffolds to promote tissue repair and regeneration. Due to their unique composition and structure, microneedles have attracted extensive attention in various tissues regeneration, including skin wound, corneal injury, myocardial infarction, endometrial injury, and spinal cord injury et al. Microneedles with micro-needle structure can effectively penetrate the barriers of necrotic tissue or biofilm, therefore improving the bioavailability of drugs. The use of microneedles to deliver bioactive molecules, mesenchymal stem cells, and growth factors in situ allows for targeted tissue and better spatial distribution. At the same time, microneedles can also provide mechanical support or directional traction for tissue, thus accelerating tissue repair. This review summarized the research progress of microneedles for in situ tissue regeneration over the past decade. At the same time, the shortcomings of existing researches, future research direction and clinical application prospect were also discussed.

Microneedle-based interstitial fluid extraction for drug analysis: Advances, challenges, and prospects

Similar to blood, interstitial fluid (ISF) contains exogenous drugs and biomarkers and may therefore substitute blood in drug analysis. However, current ISF extraction techniques require bulky instruments and are both time-consuming and complicated, which has inspired the development of viable alternatives such as those relying on skin or tissue puncturing with microneedles. Currently, microneedles are widely employed for transdermal drug delivery and have been successfully used for ISF extraction by different mechanisms to facilitate subsequent analysis. The integration of microneedles with sensors enables in situ ISF analysis and specific compound monitoring, while the integration of monitoring and delivery functions in wearable devices allows real-time dose modification. Herein, we review the progress in drug analysis based on microneedle-assisted ISF extraction and discuss the related future opportunities and challenges.

Research progress on detachable microneedles for advanced applications

INTRODUCTION

Microneedles (MNs) have undergone great advances in transdermal drug delivery, and commercialized MN applications are currently available in vaccination and cosmetic products. Despite the development of MN technologies, common limitations of MN products still exist. Typical MN patches are applied to target tissues, where the substrate of an MN patch must remain until the drug is delivered, which reduces patients' compliance and hinders the applicability of the MN technique to many diseases in various tissues. MN research is ongoing to solve this issue.

AREAS COVERED

Most recent MNs developed by combining various biomaterials with appropriate fabrication processes are detachable MNs (DeMNs). Because of advances in biomaterials and fabrication techniques, various DeMNs have been rapidly developed. In this review, we discuss four types of DeMN: substrate-separable, multi-layered, crack-inducing, and shell DeMN. These DeMNs deliver various therapeutic agents ranging from small- and large-molecular-weight drugs to proteins and even stem cells for regeneration therapy. Furthermore, DeMNs are applied to skin as well as non-transdermal tissues.

EXPERT OPINION

It has become increasingly evident that novel MN technologies can be expected in terms of designs, fabrication methods, materials, and even possible application sites given the recent advances in DeMNs.

Adhesive hydrogel wrap loaded with Netrin-1-modified adipose-derived stem cells: An effective approach against periarterial inflammation after endovascular intervention

Endovascular interventions, such as balloon dilation and stent implantation, are currently recommended as the primary treatment for patients with peripheral artery disease (PAD), greatly improving patient prognosis. However, the consequent lumen restenosis that occurs after endovascular interventions has become an important clinical problem. Inflammation has been proven to be crucial to postoperative restenosis. In previous studies we have identified that Netrin-1-modified adipose-derived stem cells (N-ADSCs) transplantation is an effective anti-inflammatory strategy to repair vascular damage. Nevertheless, it remained to be explored how one could constantly deliver N-ADSCs onto damaged arteries. Therefore, we developed an adhesive double network (DN) hydrogel wrap loaded with N-ADSCs for sustained perivascular delivery. Inspired by the adhesion mechanism of mussels, we developed an adhesive and tough polyacrylamide/calcium-alginate/reduced graphene oxide/polydopamine (PAM/CA/rGO/PDA) hydrogel. Dopamine was attached to graphene sheets and limitedly oxidized to generate free catechol groups. The hydrogel could wrap damaged arteries and induce anti-inflammatory effects through N-ADSCs. In vitro experiments demonstrated that N-ADSCs significantly promoted the M2 polarization of macrophages to anti-inflammatory phenotypes and reduced the expression of inflammatory factors. In vivo experiments in a rat carotid artery guidewire injury model showed that the adhesive hydrogel wrap loaded with N-ADSCs could significantly reduce arterial inflammation, inhibit intimal hyperplasia and improve re-endothelialization. Altogether, this newly developed N-ADSCs-loaded hydrogel wrap provides an effective slow-releasing system, which may be a promising way to prevent and treat restenosis after endovascular interventions.

Time-dependent pathobiological and physiological changes of implanted vein grafts in a canine model

Although autologous vein grafting is essential, the high vein failure rate and specific clinical interventions are not clear, so a potential treatment is critically needed; thus, complex analyses of the relationship between pathobiological and physiological processes in preclinical are essential. The interposition of the femoral vein was performed in a canine model. Maximized expansion and velocity were measured at 8 weeks post-implantation, and a relative decrease was observed at 12 weeks. However, NI formation and NI/Media ratio significantly increased time dependently, and differences between the mechanical properties were observed. Additionally, RhoA-mediated TNF-α induced by rapid structural changes and high shear stress was confirmed. After adaptation to the arterial environment, vascular remodeling occurred by SMC proliferation and differentiation, apoptosis and autophagy were induced through YAP activity without vasodilation and RhoA activity. Our results show that understanding pathobiological processes in which time-dependent physiological changes contribute to vein failure can lead to a potential strategy. The implanted vein graft within the arterial environment undergoes pathobiological processes through RhoA and YAP activity, leading to pathophysiological changes.

Highly flexible and porous silk fibroin microneedle wraps for perivascular drug delivery

Various perivascular drug delivery techniques have been demonstrated for localized post-treatment of intimal hyperplasia: a vascular inflammatory response caused by endothelial damages. Although most perivascular devices have focused on controlling the delivery duration of anti-proliferation drug, the confined and unidirectional delivery of the drug to the target tissue has become increasingly important. In addition, careful attention should also be paid to the luminal stability and the adequate exchange of vascular protein or cell between the blood vessel and extravascular tissue to avoid any side effect from the long-term application of any perivascular device. Here, a highly flexible and porous silk fibroin microneedle wrap (Silk MN wrap) is proposed to directly inject antiproliferative drug to the anastomosis sites while ensuring sufficient vascular exchanges. Drug-embedded silk MNs were transfer-molded on a highly flexible and porous silk wrap. The enhanced cell compatibility, molecular permeability, and flexibility of silk MN wrap guaranteed the structural integrity of blood vessels. Silk wrap successfully supported the silk MNs and induced multiple MN penetration to the target tissue. Over 28 days, silk MN wrap significantly inhibited intimal hyperplasia with a 62.1% reduction in neointimal formation.

Microneedle-mediated therapy for cardiovascular diseases

Cardiovascular diseases remain a leading cause of global disease burden. To date, the limited drug delivery efficacy confines the therapeutic effect in most conventional approaches, such as intramyocardial injections and vascular devices, due to short-term drug release and low retention within the disease sites. As a typical transdermal medical device with a minimally invasive manner and controlled/sustained drug release pattern, microneedles have gained momentum in the field of cardiovascular therapy, from which several cardiovascular diseases have been benefited to the ultimate therapeutic effects. In this concise review, strategies based on the microneedles for the treatments of cardiovascular diseases are introduced, mainly focus on hypertension, atherosclerosis, thrombus, and myocardial diseases. The limitations at the present stage and perspectives of the next-generation microneedles for cardiovascular therapy are also discussed.

PLCL vascular external sheath carrying prednisone for improving patency rate of the vein graft

Coronary artery bypass graft surgery (CABG) is an impactful treatment for coronary heart disease. Intimal hyperplasia is the central reason for the restenosis of vein grafts after CABG. The introduction of external vascular sheaths around VGs (VGs) can effectively inhibit intimal hyperplasia and ensure the patency of VGs. In this study, the well-known biodegradable copolymer poly (ε-caprolactone-co-L, L-lactide) (PLCL) was electrospun into high porosity external sheaths. The prednisone loaded in the PLCL sheath was slowly released during the degradation process of PLCL. Under the combined effects of sheath and prednisone, intimal hyperplasia was inhibited. For the cell experiments, all sheaths show low cytotoxicity to L929 cells at different concentrations at different time intervals. The ultrasonography and histological results showed prominent dilation and intimal hyperplasia of VG without sheath after two months of surgery. But there was no dilation in PLCL and PLCL_Prednisone groups. Notably, the prednisone-loaded sheath group exhibited efficacy in inhibiting intimal hyperplasia and ensured graft patency.

Immediate detachment of microneedles by interfacial fracture for sustained delivery of a contraceptive hormone in the skin

Despite their high efficacy and safety, long-acting contraceptive methods are underutilized among women in some settings because they usually require injection or implantation by healthcare personnel. Here, we report a self-administrable microneedle (MN) patch for the rapid administration of a sustained-release contraceptive hormone delivery system into the skin that increases the simplicity and reliability of the MN delivery. We developed an immediate microneedle detachment system using a porous patch backing that has sufficient strength during MN insertion into skin under compression, but enables immediate detachment (< 1 s) of the MNs due to fracture at the MN - backing interface upon patch removal under tension from the skin surface. After patch application, the removed patch produced no biohazardous sharps waste, and was designed to achieve long-acting contraception by formulating poly(lactic-co-glycolic acid) MNs to slowly release the contraceptive hormone levonorgestrel for up to 1 month. Our combined strategy using immediate MN detachment in the skin and sustained drug delivery from the MNs could facilitate greater access to long-acting contraception by providing a simple and convenient option for self-administered, long-acting contraception.

Microneedles for drug delivery: recent advances in materials and geometry for preclinical and clinical studies

INTRODUCTION

A microneedle array patch (MAP) has been studied as a means for delivering drugs or vaccines and has shown superior delivery efficiency compared to the conventional transdermal drug delivery system (TDD). This paper reviews recent advancements in the development of MAPs, with a focus on their size, shapes, and materials in preclinical and clinical studies for pharmaceutics.

AREA COVERED

We classified MAPs for drug delivery into four types: coated, dissolving, separable, and swellable. We covered their recent developments in materials and geometry in preclinical and clinical studies.

EXPERT OPINION

The design of MAPs needs to be determined based on what properties would be effective for the target diseases and purposes. In addition, in preclinical studies, it is necessary to consider not only the novelty of the formulations but also the feasibility of clinical application. Currently, clinical studies of microneedles loaded with various drugs and vaccines are in progress. When the regulation of pharmaceutical microneedles is established and more clinical studies are published, more drugs will be developed as microneedle products and clinical research will proceed. With these considerations, the microneedle array patch will be a better option for drug delivery.

Rapid biodegradable microneedles with allergen reservoir for skin allergy test

With the increasing allergy cases worldwide, this study introduces a biodegradable microneedle system to facilitate allergy testing process. Dissolving microneedle provides a minimally invasive manner to go through skin barrier while avoiding needle phobia among patents, especially children. The microneedles were fabricated using copolymer polyvinylpyrrolidone-co-methacrylic acid (PVP-MAA) material. To ensure the successful insertion of microneedles into the skin, we tailored the mechanical strength of the copolymer by adjusting the weight ratio of two constituted polymers. A reservoir was designed to load allergy specimen for the allergy test. This system is expected to offer a simple and effective allergy testing that can facilitate the allergy testing protocol.

A Patch of Detachable Hybrid Microneedle Depot for Localized Delivery of Mesenchymal Stem Cells in Regeneration Therapy

Mesenchymal stem cells (MSCs) have been widely used for regenerative therapy. In most current clinical applications, MSCs are delivered by injection but face significant issues with cell viability and penetration into the target tissue due to a limited migration capacity. Some therapies have attempted to improve MSC stability by their encapsulation within biomaterials; however, these treatments still require an enormous number of cells to achieve therapeutic efficacy due to low efficiency. Additionally, while local injection allows for targeted delivery, injections with conventional syringes are highly invasive. Due to the challenges associated with stem cell delivery, a local and minimally invasive approach with high efficiency and improved cell viability is highly desired. In this study, we present a detachable hybrid microneedle depot (d-HMND) for cell delivery. Our system consists of an array of microneedles with an outer poly(lactic-co-glycolic) acid (PLGA) shell and an internal gelatin methacryloyl (GelMA)-MSC mixture (GMM). The GMM was characterized and optimized for cell viability and mechanical strength of the d-HMND required to penetrate mouse skin tissue was also determined. MSC viability and function within the d-HMND was characterized in vitro and the regenerative efficacy of the d-HMND was demonstrated in vivo using a mouse skin wound model.

Smart Microneedles for Therapy and Diagnosis

Microneedles represent a cutting-edge and idea-inspiring technology in biomedical engineering, which have attracted increasing attention of scientific researchers and medical staffs. Over the past decades, numerous great achievements have been made. The fabrication process of microneedles has been simplified and becomes more precise, easy-to-operate, and reusable. Besides, microneedles with various features have been developed and the microneedle materials have greatly expanded. In recent years, efforts have been focused on generating smart microneedles by endowing them with intriguing functions such as adhesion ability, responsiveness, and controllable drug release. Such improvements enable the microneedles to take an important step in practical applications including household drug delivery devices, wearable biosensors, biomedical assays, cell culture, and microfluidic chip analysis. In this review, the fabrication strategies, distinctive properties, and typical applications of the smart microneedles are discussed. Recent accomplishments, remaining challenges, and future prospects are also presented.

Non-transdermal microneedles for advanced drug delivery

Microneedles (MNs) have been used to deliver drugs for over two decades. These platforms have been proven to increase transdermal drug delivery efficiency dramatically by penetrating restrictive tissue barriers in a minimally invasive manner. While much of the early development of MNs focused on transdermal drug delivery, this technology can be applied to a variety of other non-transdermal biomedical applications. Several variations, such as multi-layer or hollow MNs, have been developed to cater to the needs of specific applications. The heterogeneity in the design of MNs has demanded similar variety in their fabrication methods; the most common methods include micromolding and drawing lithography. Numerous materials have been explored for MN fabrication which range from biocompatible ceramics and metals to natural and synthetic biodegradable polymers. Recent advances in MN engineering have diversified MNs to include unique shapes, materials, and mechanical properties that can be tailored for organ-specific applications. In this review, we discuss the design and creation of modern MNs that aim to surpass the biological barriers of non-transdermal drug delivery in ocular, vascular, oral, and mucosal tissue.

A Perspective on Microneedle-Based Drug Delivery and Diagnostics in Paediatrics

Microneedles (MNs) have been extensively explored in the literature as a means to deliver drugs in the skin, surpassing the stratum corneum permeability barrier. MNs are potentially easy to produce and may allow the self-administration of drugs without causing pain or bleeding. More recently, MNs have been investigated to collect/assess the interstitial fluid in order to monitor or detect specific biomarkers. The integration of these two concepts in closed-loop devices holds the promise of automated and minimally invasive disease detection/monitoring and therapy. These assure low invasiveness and, importantly, open a window of opportunity for the application of population-specific and personalised therapies.

Microneedle Coating Methods: A Review with a Perspective

A coated microneedle array comprises sharp micrometer-sized needle shafts attached to a base substrate and coated with a drug on their surfaces. Coated microneedles are under investigation for drug delivery into the skin and other tissues, and a broad assortment of active materials, including small molecules, peptides, proteins, deoxyribonucleic acids, and viruses, have been coated onto microneedles. To coat the microneedles, different methods have been developed. Some coating methods achieve selective coating of just the microneedle shafts, whereas other methods coat not only microneedle shafts but also the array base substrate. Selective coating of just the microneedle shafts is more desirable since it provides control over drug dosage, prevents drug waste, and offers high delivery efficiency. Different excipients are added to the coating liquid to modulate its viscosity and surface tension in order to achieve uniform coatings on microneedles. Coated microneedles have been used in a broad range of biomedical applications. To highlight these different applications, a table summarizing the different active materials and the amounts coated on microneedles is provided. We also discuss factors that should be considered when deciding suitability of coated microneedles for new-drug delivery applications. In recent years, many coated microneedles have been investigated in human clinical trials, and there is now a strong effort to bring the first coated microneedle-based product to market.

Three-Step Thermal Drawing for Rapid Prototyping of Highly Customizable Microneedles for Vascular Tissue Insertion

Microneedles (MNs) have been extensively developed over the last two decades, and highly efficient drug delivery was demonstrated with their minimal invasiveness via a transdermal route. Recently, MNs have not only been applied to the skin but also to other tissues such as blood vessels, scleral tissue, and corneal tissue. In addition, the objective of the MN application has been diversified, ranging from drug delivery to wound closure and biosensing. However, since most MN fabrication methods are expensive and time-consuming, they are inappropriate to prototype MNs for various tissues that have different and complex anatomies. Although several drawing-based techniques have been introduced for rapid MN production, they fabricated MNs with limited shapes, such as thin MNs with wide bases. In this study, we propose a three-step thermal drawing for rapid, prototyping MNs that can have a variety of shapes and can be fabricated on curved surfaces. Based on the temperature control of polymer bridge formation during thermal drawing, the body profile and aspect ratios of MNs were conveniently controlled, and the effect of temperature control on the body profile of MNs was explained. Thermally drawn MNs with different shapes were fabricated both on flat and curved surfaces, and they were characterized in terms of their mechanical properties and insertion into vascular tissue to find an optimal shape for vascular tissue insertion.

Near-infrared light-mediated and nitric oxide-supplied nanospheres for enhanced synergistic thermo-chemotherapy

Synergistic thermo-chemotherapy based multiple stimuli-responsive drug delivery systems have achieved significant improvement of cancer curative effects compared with single modality treatment. Nevertheless, the efficacy of thermo-chemotherapy is often reduced in drug-resistant tumors and the therapy method is unexpectedly associated with potential toxicity by utilizing poorly degradable materials. Here, we report a simple approach to encapsulate three drug payloads into multi-sensitive and degradable nanospheres (SDC@NS) to achieve anticancer effects. SDC@NS comprise a photothermal agent (cypate), an anticancer agent (doxorubicin), and a nitric oxide donor (SNAP) to achieve controllable drugs release in high concentration glutathione or under near-infrared light (NIR) irradiation. Hyperthermia from NIR-mediated cypate can accelerate cancer cell apoptosis in vitro and tumor tissue ablation in vivo. Furthermore, our results also confirmed that the nitric oxide-based SDC@NS showed significant cytotoxicity compared to the nitric oxide absent group (denoted as DC@NS) and an enhanced chemotherapy effect in vivo. The photothermal effect and payloads can synchronously realize cancer therapy and provide a new insight into the enhanced synergistic therapeutic effect.

Functionalized microneedles for continuous glucose monitoring

Microneedles (MNs) have been established as promising medical devices as they are minimally invasive, cause less pain, and can be utilized for self-administration of drugs by patients. There has been rapid development in MNs for transdermal monitoring and diagnostic systems, following the active research on fabrication methods and applications for drug delivery. In this paper, recent investigations on bio-sensing using MNs are reviewed in terms of the applicability to continuous glucose monitoring system (CGMS), which is one of the main research focuses of medical engineering technologies. The trend of the functionalized MNs can be categorized as follows: (i) as a sensing probe, and (ii) as a biological fluid collector. MNs as in vivo sensors are mainly integrated or coated with conductive materials to have the function as electrodes. MNs as fluid collectors are given a certain geometrical design, such as a hollow and porous structure aided by a capillary action or negative pressure, to extract the interstitial fluids or blood for ex vivo analysis. For realization of CGMS with MNs, a long-term accurate measurement by the MN-based sensing probe or a fluidic connection between the MN-based fluid collector and the existing microfluidic measurement systems should be investigated.