Cell and fluid sampling microneedle patches for monitoring skin-resident immunity

Turbulence-enhanced microneedle immunoassay platform (TMIP) for high-precision biomarker detection from skin interstitial fluid

Conventional diagnostic methods for biomarker detection often require invasive procedures and exhibit limited reproducibility and sensitivity. In this study, the turbulence-enhanced microneedle immunoassay platform (TMIP) was designed to enhance the performance and accuracy of biomarker detection in skin interstitial fluid (ISF). TMIP combines a bullet-shaped microneedle (MN) array for minimally invasive biomarker capture, a microfluidic device for MN-mediated immunoassay process simplification, and a star-shaped magnetic stirrer tool (MST) to facilitate efficient washing. By targeting S100 calcium-binding protein B (S100B), a diagnostic biomarker for melanoma, TMIP demonstrated substantial improvements in reproducibility, reducing signal deviations by up to 55 % compared to manual operation. The application of nanoporous MNs (NPMNs) achieved a low detection limit of 20 pg/mL with a high linearity (R2 = 0.9758). Validation using a gelatin phantom mimicking human skin confirmed TMIP's ability to achieve improved reproducibility and sensitivity. Furthermore, TMIP successfully detected S100B with high reproducibility in both the phantom (R2 = 0.97523) and melanoma-expressing mice within a rapid incubation time of 1 min. TMIP enables the detection of biomarkers with remarkable reproducibility and sub-nanogram sensitivity by simplifying the analysis process and enhancing reagent washing through turbulence. These features suggest that TMIP has the potential to serve as an efficient and reliable tool for biomarker detection in skin ISF.

Leveraging tissue-resident memory T cells for non-invasive immune monitoring via microneedle skin patches

Detecting antigen-specific lymphocytes is crucial for immune monitoring in the setting of vaccination, infectious disease, cancer, and autoimmunity. However, their low frequency and dispersed distribution across lymphoid organs, peripheral tissues, and blood pose challenges for reliable detection. To address this issue, we developed a strategy exploiting the functions of tissue-resident memory T cells (TRMs) to concentrate target circulating immune cells in the skin and then sample these cells non-invasively using a microneedle (MN) skin patch. TRMs were first induced at a selected skin site through initial sensitization with a selected antigen. Subsequently, these TRMs were restimulated by intradermal inoculation of a small quantity of the same antigen to trigger the "alarm" and immune recruitment functions of these cells, leading to accumulation of antigen-specific T cells from the circulation over several days. In mouse models of vaccination, we show that application of MN patches coated with an optimized hydrogel layer for cell and fluid sampling to this skin site allowed effective isolation of thousands of live antigen-specific lymphocytes as well as innate immune cells. In a human subject with allergic contact dermatitis, stimulation of TRMs with allergen followed by MN patch application allowed the recovery of diverse lymphocyte populations that were absent from untreated skin sites. These results suggest that TRM restimulation coupled with microneedle patch sampling can be used to obtain a window into both local and systemic antigen-specific immune cell populations in a noninvasive manner that could be readily applied to a wide range of disease or vaccination settings.

Microneedle Array-Based Dermal Interstitial Fluid Biopsy for Cancer Diagnosis: Advances and Challenges

Current early cancer diagnostic technologies, such as imaging, molecular tests, endoscopic techniques, and biopsies, face considerable challenges in low-and middle-income countries (LMICs) due to high costs, procedural complexity, and limited resource access. Microneedle-based liquid biopsy for skin interstitial fluid (ISF) offers a practical and minimally invasive alternative for cancer diagnosis in these settings. This review systematically examines ISF liquid biopsy methods for their effectiveness in capturing cancer biomarkers directly from the skin and assesses their potential to address diagnostic needs in low-resource environments. Recent innovations in microneedle design and ISF underscore their potential in enabling early, accessible cancer detection tailored to LMICs' needs. Additionally, integrating artificial intelligence (AI) for data interpretation is proposed as a way to enhance diagnostic accuracy and enable real-time point-of-care (POC) applications. Collectively, these advances illustrate a flexible, scalable model for accessible cancer diagnostics, with significant implications for improving early detection and healthcare quality in resource-limited environments.

Bioresponsive Immunotherapeutic Materials

The human immune system is an interaction network of biological processes, and its dysfunction is closely associated with a wide array of diseases, such as cancer, infectious diseases, tissue damage, and autoimmune diseases. Manipulation of the immune response network in a desired and controlled fashion has been regarded as a promising strategy for maximizing immunotherapeutic efficacy and minimizing side effects. Integration of "smart" bioresponsive materials with immunoactive agents including small molecules, biomacromolecules, and cells can achieve on-demand release of agents at targeted sites to reduce overdose-related toxicity and alleviate off-target effects. This review highlights the design principles of bioresponsive immunotherapeutic materials and discusses the critical roles of controlled release of immunoactive agents from bioresponsive materials in recruiting, housing, and manipulating immune cells for evoking desired immune responses. Challenges and future directions from the perspective of clinical translation are also discussed.

Recent progress of microneedles in transdermal immunotherapy: A review

Since human skin is an immune organ, a large number of immune cells are distributed in the epidermis and the dermis of the skin. Transdermal immunotherapy shows great therapeutic advantages in innate immunotherapy and adaptive immunotherapy. To solve the problem that macromolecules are difficult to penetrate into the skin, the microneedle technology can directly break through the skin barrier using micron-sized needles in a non-invasive and painless way for transdermal drug delivery. Therefore, it is considered to be an effective technology to increase drug transdermal absorption. In this review, the types of preparation, the combinations with different techniques and the mechanisms of microneedles in transdermal immunotherapy were summarized. Compared with traditional immunotherapy like intramuscular injection and subcutaneous injection, the microneedle has many advantages in transdermal immunotherapy, such as reducing patient pain, enhancing vaccine stability, and inducing stronger immune responses. Although there are still some limitations to be solved, the application of microneedle technology in transdermal immunotherapy is undoubtedly a promising means of drug delivery.

Microneedle patch casting using a micromachined carbon master for enhanced drug delivery

For successful treatment of diseases, sufficient therapeutics must be provided to the body. Microneedle applications in therapeutic delivery and analytics sampling are restricted because of various issues, including smaller area for drug loading and analytics sampling. To achieve sufficient drug loading and analytics sampling and improve drug penetration while maintaining painless administration, patch-type microneedle arrays were designed and fabricated using polymer casting from a conical cavity mold. Microcavities were formed on a carbon plate via micromechanical machining. A porous polymer layer was coated on a microneedle patch (MNP). The pores of the porous polymer layer provided space and channels for drug delivery. A pH-sensitive polymer layer was employed to cap the porous polymer layer, which prevented drug leakage during storage and provided a stimulus drug release in response to body pH conditions. The drug can be delivered through holes connected to both sides of the patch. The drug release of the MNP was investigated in vitro and in vivo and showed conceptual proof that these MNs have the potential to enhance treatment protocols for various diseases with the flexibility of coating and therapeutic materials and offer significant scope for further variations and advancement.

Sensing patches for biomarker identification in skin-derived biofluids

In conventional clinical disease diagnosis and screening based on biomarker detection, most analysis samples are collected from serum, blood. However, these invasive collection methods require specific instruments, professionals, and may lead to infection risks. Additionally, the diagnosis process suffers from untimely results. The identification of skin-related biomarkers plays an unprecedented role in early disease diagnosis. More importantly, these skin-mediated approaches for collecting biomarker-containing biofluid samples are noninvasive or minimally invasive, which is more preferable for point-of-care testing (POCT). Therefore, skin-based biomarker detection patches have been promoted, owing to their unique advantages, such as simple fabrication, desirable transdermal properties and no requirements for professional medical staff. Currently, the skin biomarkers extracted from sweat, interstitial fluid (ISF) and wound exudate, are achieved with wearable sweat patches, transdermal MN patches, and wound patches, respectively. In this review, we detail these three types of skin patches in biofluids collection and diseases-related biomarkers identification. Patch classification and the corresponding manufacturing as well as detection strategies are also summarized. The remaining challenges in clinical applications and current issues in accurate detection are discussed for further advancement of this technology (Scheme 1).

Microneedle-Mediated Delivery of Immunomodulators Restores Immune Privilege in Hair Follicles and Reverses Immune-Mediated Alopecia

Disorders in the regulatory arm of the adaptive immune system result in autoimmune-mediated diseases. While systemic immunosuppression is the prevailing approach to manage them, it fails to achieve long-lasting remission due to concomitant suppression of the regulatory arm and carries the risk of heightened susceptibility to infections and malignancies. Alopecia areata is a condition characterized by localized hair loss due to autoimmunity. The accessibility of the skin allows local rather than systemic intervention to avoid broad immunosuppression. It is hypothesized that the expansion of endogenous regulatory T cells (Tregs) at the site of antigen encounter can restore the immune balance and generate a long-lasting tolerogenic response. A hydrogel microneedle (MN) patch is therefore utilized for delivery of CCL22, a Treg-chemoattractant, and IL-2, a Treg survival factor to amplify them. In an immune-mediated murine model of alopecia, local bolstering of Treg numbers is shown, leading to sustained hair regrowth and attenuation of inflammatory pathways. In a humanized skin transplant mouse model, expansion of Tregs within human skin is confirmed without engendering peripheral immunosuppression. The patch offers high-loading capacity and shelf-life stability for prospective clinical translation. By harmonizing immune responses locally, the aim is to reshape the landscape of autoimmune skin disease management.

Integrating microneedles and sensing strategies for diagnostic and monitoring applications: The state of the art

Microneedles (MNs) offer minimally-invasive access to interstitial fluid (ISF) - a potent alternative to blood in terms of monitoring physiological analytes. This property is particularly advantageous for the painless detection and monitoring of drugs and biomolecules. However, the complexity of the skin environment, coupled with the inherent nature of the analytes being detected and the inherent physical properties of MNs, pose challenges when conducting physiological monitoring using this fluid. In this review, we discuss different sensing mechanisms and highlight advancements in monitoring different targets, with a particular focus on drug monitoring. We further list the current challenges facing the field and conclude by discussing aspects of MN design which serve to enhance their performance when monitoring different classes of analytes.

Inflammatory macrophage reprogramming strategy of fucoidan microneedles-mediated ROS-responsive polymers for rheumatoid arthritis

During the pathogenesis of rheumatoid arthritis, inflammatory cells usually infiltrate synovial tissues, notably, M1-type macrophages, whose redox imbalance leads to the degradation of joint structures and deterioration of function. Natural active products play a vital role in immune modulation and antioxidants. In this study, we constructed a ROS-responsive nanoparticle called FTL@SIN, which consists of fucoidan (Fuc) and luteolin (Lut) connected by a ROS-responsive bond, Thioketal (TK), and encapsulated with an anti-rheumatic drug, Sinomenine (SIN), for synergistic anti-inflammatory effects. The FTL@SIN is then dispersed in high molecular weight Fuc-fabricated dissolvable microneedles (FTL@SIN MNs) for local administration. Therapy of FTL@SIN MNs afforded a significant decrease in macrophage inflammation while decreasing key pro-inflammatory cytokines and repolarizing M1 type to M2 type, thereby ameliorating synovial inflammation, and promoting cartilage repair. Additionally, our investigations have revealed that Fucoidan (Fuc) demonstrates synergistic effects, exhibiting superior mechanical strength and enhanced physical stability when compared to microneedles formulated solely with hyaluronic acid. This study combines nanomedicine with traditional Chinese medicine, a novel drug delivery strategy that presents a promising avenue for therapeutic intervention in rheumatoid arthritis.

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.

Unravelling the role of microneedles in drug delivery: Principle, perspectives, and practices

In recent year, the research of transdermal drug delivery systems has got substantial attention towards the development of microneedles (MNs). This shift has occurred due to multifaceted advantages of MNs as they can be utilized to deliver the drug deeper to the skin with minimal invasion, offer successful delivery of drugs and biomolecules that are susceptible to degradation in gastrointestinal tract (GIT), act as biosensors, and help in monitoring the level of biomarkers in the body. These can be fabricated into different types based on their applications as well as material for fabrication. Some of their types include solid MNs, hollow MNs, coated MNs, hydrogel forming MNs, and dissolving MNs. These MNs deliver the therapeutics via microchannels deeper into the skin. The coated and hollow MNs have been found successful. However, they suffer from poor drug loading and blocking of pores. In contrast, dissolving MNs offer high drug loading. These MNs have also been utilized to deliver vaccines and biologicals. They have also been used in cosmetics. The current review covers the different types of MNs, materials used in their fabrication, properties of MNs, and various case studies related to their role in delivering therapeutics, monitoring level of biomarkers/hormones in body such as insulin. Various patents and clinical trials related to MNs are also covered. Covered are the major bottlenecks associated with their clinical translation and potential future perspectives.

Hydrogel-Coated SERS Microneedles for Drug Monitoring in Dermal Interstitial Fluid

In vivo drug monitoring is crucial for evaluating the effectiveness and safety of drug treatment. Blood sampling and analysis is the current gold standard but needs professional skills and cannot meet the requirements of point-of-care testing. Dermal interstitial fluid (ISF) showed great potential to replace blood for in vivo drug monitoring; however, the detection was challenging, and the drug distribution behavior in ISF was still unclear until now. In this study, we proposed surface-enhanced Raman spectroscopy (SERS) microneedles (MNs) for the painless and real-time analysis of drugs in ISF after intravenous injection. Using methylene blue (MB) and mitoxantrone (MTO) as model drugs, the innovative core-satellite structured Au@Ag SERS substrate, hydrogel coating over the MNs, rendered sensitive and quantitative drug detection in ISF of mice within 10 min. Based on this technique, the pharmacokinetics of the two drugs in ISF was investigated and compared with those in blood, where the drugs were analyzed via liquid chromatography-mass spectrometry. It was found that the MB concentration in ISF and blood was comparable, whereas the concentration of MTO in ISF was 2-3 orders of magnitude lower than in blood. This work proposed an efficient tool for ISF drug monitoring. More importantly, it experimentally proved that the penetration ratio of blood to ISF was drug-dependent, providing insightful information into the potential of ISF as a blood alternative for in vivo drug detection.

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.

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.

The therapeutic potential of immunoengineering for systemic autoimmunity

Disease-modifying drugs have transformed the treatment options for many systemic autoimmune diseases. However, an evolving understanding of disease mechanisms, which might vary between individuals, is paving the way for the development of novel agents that operate in a patient-tailored manner through immunophenotypic regulation of disease-relevant cells and the microenvironment of affected tissue domains. Immunoengineering is a field that is focused on the application of engineering principles to the modulation of the immune system, and it could enable future personalized and immunoregulatory therapies for rheumatic diseases. An important aspect of immunoengineering is the harnessing of material chemistries to design technologies that span immunologically relevant length scales, to enhance or suppress immune responses by re-balancing effector and regulatory mechanisms in innate or adaptive immunity and rescue abnormalities underlying pathogenic inflammation. These materials are endowed with physicochemical properties that enable features such as localization in immune cells and organs, sustained delivery of immunoregulatory agents, and mimicry of key functions of lymphoid tissue. Immunoengineering applications already exist for disease management, and there is potential for this new discipline to improve disease modification in rheumatology.

Design and fabrication of customizable microneedles enabled by 3D printing for biomedical applications

Microneedles (MNs) is an emerging technology that employs needles ranging from 10 to 1000 μm in height, as a minimally invasive technique for various procedures such as therapeutics, disease monitoring and diagnostics. The commonly used method of fabrication, micromolding, has the advantage of scalability, however, micromolding is unable to achieve rapid customizability in dimensions, geometries and architectures, which are the pivotal factors determining the functionality and efficacy of the MNs. 3D printing offers a promising alternative by enabling MN fabrication with high dimensional accuracy required for precise applications, leading to improved performance. Furthermore, enabled by its customizability and one-step process, there is propitious potential for growth for 3D-printed MNs especially in the field of personalized and on-demand medical devices. This review provides an overview of considerations for the key parameters in designing MNs, an introduction on the various 3D-printing techniques for fabricating this new generation of MNs, as well as highlighting the advancements in biomedical applications facilitated by 3D-printed MNs. Lastly, we offer some insights into the future prospects of 3D-printed MNs, specifically its progress towards translation and entry into market.

Nanovaccines for Advancing Long-Lasting Immunity against Infectious Diseases

Infectious diseases, particularly life-threatening pathogens such as small pox and influenza, have substantial implications on public health and global economies. Vaccination is a key approach to combat existing and emerging pathogens. Immunological memory is an essential characteristic used to evaluate vaccine efficacy and durability and the basis for the long-term effects of vaccines in protecting against future infections; however, optimizing the potency, improving the quality, and enhancing the durability of immune responses remains challenging and a focus for research involving investigation of nanovaccine technologies. In this review, we describe how nanovaccines can address the challenges for conventional vaccines in stimulating adaptive immune memory responses to protect against reinfection. We discuss protein and nonprotein nanoparticles as useful antigen platforms, including those with highly ordered and repetitive antigen array presentation to enhance immunogenicity through cross-linking with multiple B cell receptors, and with a focus on antigen properties. In addition, we describe how nanoadjuvants can improve immune responses by providing enhanced access to lymph nodes, lymphnode targeting, germinal center retention, and long-lasting immune response generation. Nanotechnology has the advantage to facilitate vaccine induction of long-lasting immunity against infectious diseases, now and in the future.

Exploiting Unique Features of Microneedles to Modulate Immunity

Microneedle arrays (MNAs) are small patches containing hundreds of short projections that deliver signals directly to dermal layers without causing pain. These technologies are of special interest for immunotherapy and vaccine delivery because they directly target immune cells concentrated in the skin. The targeting abilities of MNAs result in efficient immune responses-often more protective or therapeutic-compared to conventional needle delivery. MNAs also offer logistical benefits, such as self-administration and transportation without refrigeration. Thus, numerous preclinical and clinical studies are exploring these technologies. Here the unique advantages of MNA, as well as critical challenges-such as manufacturing and sterility issues-the field faces to enable widespread deployment are discussed. How MNA design parameters can be exploited for controlled release of vaccines and immunotherapies, and the application to preclinical models of infection, cancer, autoimmunity, and allergies are explained. Specific strategies are also discussed to reduce off-target effects compared to conventional vaccine delivery routes, and novel chemical and manufacturing controls that enable cargo stability in MNAs across flexible intervals and temperatures. Clinical research using MNAs is then examined. Drawbacks of MNAs and the implications, and emerging opportunities to exploit MNAs for immune engineering and clinical use are concluded.

Strategies to develop polymeric microneedles for controlled drug release

The remarkable appeal of microneedle controlled-release systems has captivated both the academic community and pharmaceutical industry due to their great potential for achieving spatiotemporally controlled release, coupled with their the minimally invasive nature and ease of application. Over the years, scientists have dedicated their efforts to advancing microneedle systems by manipulating the physicochemical properties of matrix materials, refining microneedle designs, and interfacing with external devices to provide tailored drug release profiles in a spatiotemporally controllable manner. Expanding upon our understanding of drug release mechanisms from polymeric microneedles, which include diffusion, swelling, degradation, triggering, and targeting, there is a growing focus on manipulating the location and rate of drug release through innovative microneedle designs. This burgeoning field of microneedle-based drug delivery systems offers further prospects for precise control over drug release. The design strategies of polymeric microneedle systems for temporally controlled and locally targeted release, as well as the delivery mechanisms by which drugs can be released from a microneedle system are critically reviewed in this work. Furthermore, this review also puts forward some perspectives on the potential and challenges involved in translating these microneedle-based delivery systems into the next generation therapies.

Microneedle-based cell delivery and cell sampling for biomedical applications

Cell-based therapeutics are novel therapeutic strategies that can potentially treat many presently incurable diseases through novel mechanisms of action. Cell therapies may benefit from the ease, safety, and efficacy of administering therapeutic cells. Despite considerable recent technological and biological advances, several barriers remain to the clinical translation and commercialization of cell-based therapies, including low patient compliance, personal handling inconvenience, poor biosafety, and limited biocompatibility. Microneedles (MNs) are emerging as a promising biomedical device option for improved cell delivery with little invasion, pain-free administration, and simplicity of disposal. MNs have shown considerable promise in treating a wide range of diseases and present the potential to improve cell-based therapies. In this review, we first summarized the latest advances in the various types of MNs developed for cell delivery and cell sampling. Emphasis was given to the design and fabrication of various types of MNs based on their structures and materials. Then we focus on the recent biomedical applications status of MNs-mediated cell delivery and sampling, including tissue repair (wound healing, heart repair, and endothelial repair), cancer treatment, diabetes therapy, cell sampling, and other applications. Finally, the current status of clinical application, potential perspectives, and the challenges for clinical translation are also highlighted.

Hydrogel-Forming Microneedles with Applications in Oral Diseases Management

Controlled drug delivery in the oral cavity poses challenges such as bacterial contamination, saliva dilution, and inactivation by salivary enzymes upon ingestion. Microneedles offer a location-specific, minimally invasive, and retentive approach. Hydrogel-forming microneedles (HFMs) have emerged for dental diagnostics and therapeutics. HFMs penetrate the stratum corneum, undergo swelling upon contact, secure attachment, and enable sustained transdermal or transmucosal drug delivery. Commonly employed polymers such as polyvinyl alcohol (PVA) and polyvinyl pyrrolidone are crosslinked with tartaric acid or its derivatives while incorporating therapeutic agents. Microneedle patches provide suture-free and painless drug delivery to keratinized or non-keratinized mucosa, facilitating site-specific treatment and patient compliance. This review comprehensively discusses HFMs' applications in dentistry such as local anesthesia, oral ulcer management, periodontal treatment, etc., encompassing animal experiments, clinical trials, and their fundamental impact and limitations, for example, restricted drug carrying capacity and, until now, a low number of dental clinical trial reports. The review explores the advantages and future perspectives of HFMs for oral drug delivery.

Development of a novel microneedle platform for biomarker assessment of atopic dermatitis patients

BACKGROUND

Atopic dermatitis (AD) is a chronic inflammatory skin disease whose pathogenesis, cause, and treatment have been extensively studied. The association of AD with Th2 cytokines is well known; therefore, the analysis of this association is crucial for the diagnosis and treatment of AD. This study aimed to present a new method for measuring protein biomarkers in patients with AD, before and after treatment, using minimally invasive microneedles.

MATERIALS AND METHODS

First, hyaluronic acid-loaded microneedle patches (HA-MNs) for skin sample collection were fabricated. Next, after Institutional Review Board approval, 20 patients with AD were recruited and skin samples were taken before and after treatment using four different sampling techniques: (1) tape stripping, (2) hydrocolloid patches, (3) hollow microneedles, and (4) HA-MNs. Lastly, proteins were isolated from the collected samples, and AD-related biomarkers were analyzed by enzyme-linked immunosorbent assay.

RESULTS

Proteins were successfully extracted from the skin samples collected by tape stripping, hydrocolloid patches, and HA-MNs, except hollow microneedles. Interleukin (IL)-4, IL-13, and interferon-γ were detected in the HA-MNs only. By comparing the biomarker level correlation before and after treatment and the improvement score of the patients, we observed a significant negative correlation between IL-4 and IL-13 with an improvement in AD symptoms.

CONCLUSION

Overall, our results verified that HA-MNs can be used to effectively analyze protein levels of biomarkers from skin metabolites of patients with AD and can be applied to monitor the treatment progress of patients with AD in a minimally invasive manner.

Microneedle-Integrated Sensors for Extraction of Skin Interstitial Fluid and Metabolic Analysis

Skin interstitial fluid (ISF) has emerged as a fungible biofluid sample for blood serum and plasma for disease diagnosis and therapy. The sampling of skin ISF is highly desirable considering its easy accessibility, no damage to blood vessels, and reduced risk of infection. Particularly, skin ISF can be sampled using microneedle (MN)-based platforms in the skin tissues, which exhibit multiple advantages including minimal invasion of the skin tissues, less pain, ease of carrying, capacity for continuous monitoring, etc. In this review, we focus on the current development of microneedle-integrated transdermal sensors for collecting ISF and detecting specific disease biomarkers. Firstly, we discussed and classified microneedles according to their structural design, including solid MNs, hollow MNs, porous MNs, and coated MNs. Subsequently, we elaborate on the construction of MN-integrated sensors for metabolic analysis with highlights on the electrochemical, fluorescent, chemical chromogenic, immunodiagnostic, and molecular diagnostic MN-integrated sensors. Finally, we discuss the current challenges and future direction for developing MN-based platforms for ISF extraction and sensing applications.

Microneedle Patch for Painless Intradermal Collection of Interstitial Fluid Enabling Multianalyte Measurement of Small Molecules, SARS-CoV-2 Antibodies, and Protein Profiling

Blood sampling is a common practice to monitor health, but it entails a series of drawbacks for patients including pain and discomfort. Thus, there is a demand for more convenient ways to obtain samples. Modern analytical techniques enable monitoring of multiple bioanalytes in smaller samples, opening possibilities for new matrices, and microsampling technologies to be adopted. Interstitial fluid (ISF) is an attractive alternative matrix that shows good correlation with plasma concentration dynamics for several analytes and can be sampled in a minimally invasive and painless manner from the skin at the point-of-care. However, there is currently a lack of sampling devices compatible with clinical translation. Here, to tackle state-of-the-art limitations, a cost-effective and compact single-microneedle-based device designed to painlessly collect precisely 1.1 µL of dermal ISF within minutes is presented. The fluid is volume-metered, dried, and stably stored into analytical-grade paper within the microfluidic device. The obtained sample can be mailed to a laboratory, quantitatively analyzed, and provide molecular insights comparable to blood testing. In a human study, the possibility to monitor various classes of molecular analytes is demonstrated in ISF microsamples, including caffeine, hundreds of proteins, and SARS-CoV-2 antibodies, some being detected in ISF for the first time.

Encoded Structural Color Microneedle Patches for Multiple Screening of Wound Small Molecules

Detection of biomarkers associated with wound conditions provides in-depth healthcare information and benefits wound healing treatment. The current aim of wound detection is to achieve in situ multiple detections. Novel encoded structural color microneedle patches (EMNs) combining photonic crystals (PhCs) and microneedle arrays (MNs) for multiple wound biomarker detection in situ are described here. Using a partitioned and layered casting strategy, the EMNs can be divided into different modules and each serves for the detection of small molecules , including pH, glucose, and histamine. pH sensing is based on the interaction between hydrogen ions and carboxyl groups from hydrolyzed polyacrylamide (PAM); glucose sensing is achieved with the help of glucose-responsive fluorophenylboronic acid (FPBA); while histamine sensing relies on specific recognition of aptamers and target molecules. Owing to the responsive volume change of these three modules in the presence of target molecules, the EMNs can create structural color change and characteristic peak shift of the PhCs, thus realizing the qualitative measurement of target molecules with a spectrum analyzer. It is further demonstrated that the EMNs behave well in the multivariate detection of rat wound molecules. These features indicate that the EMNs can be valuable smart detection systems for wound status screening.

Microneedle-based transdermal detection and sensing devices

Microneedles have been expected for the construction of next-generation biosensors towards personalization, digitization, and intellectualization due to their metrics of minimal invasiveness, high integration, and favorable biocompatibility. Herein, an overview of state-of-the-art microneedle-based detection and sensing systems is presented. First, the designs of microneedle devices based on extraction mechanisms are concluded, corresponding to different geometries and materials of microneedles. Second, the targets of equipment-assisted microneedle detections are summarized, as well as the objective significance, revealing the current performance and potential scenarios of these microneedles. Third, the trend towards highly integrated sensors is elaborated by emphasizing the sensing principles (colorimetric, fluorometric and electronic manner). Finally, the key challenges to be tackled and the perspectives on future development are discussed.

Where Microneedle Meets Biomarkers: Futuristic Application for Diagnosing and Monitoring Localized External Organ Diseases

Extracellular tissue fluids are interesting biomatrices that have recently attracted scientists' interest. Many significant biomarkers for localized external organ diseases have been isolated from this biofluid. In the diagnostic and disease monitoring context, measuring biochemical entities from the fluids surrounding the diseased tissues may give more important clinical value than measuring them at a systemic level. Despite all these facts, pushing tissue fluid-based diagnosis and monitoring forward to clinical settings faces one major problem: its accessibility. Most extracellular tissue fluid, such as interstitial fluid (ISF), is abundant but hard to collect, and the currently available technologies are invasive and expensive. This is where novel microneedle technology can help tackle this significant obstacle. The ability of microneedle technology to minimally invasively access tissue fluid-containing biomarkers will enable ISF and other tissue fluid utilization in the clinical diagnosis and monitoring of localized diseases. This review attempts to present the current pursuit of the application of microneedle systems as a diagnostic and monitoring platform, along with the recent progress of biomarker detection in diagnosing and monitoring localized external organ diseases. Then, the potential use of various microneedles in future clinical diagnostics and monitoring of localized diseases is discussed by presenting the currently studied cases.

Recent Advances in Delivery Systems for Genetic and Other Novel Vaccines

Vaccination is one of the most successful and cost-effective prophylactic measures against diseases, especially infectious diseases including smallpox and polio. However, the development of effective prophylactic or therapeutic vaccines for other diseases such as cancer remains challenging. This is often due to the imprecise control of vaccine activity in vivo which leads to insufficient/inappropriate immune responses or short immune memory. The development of new vaccine types in recent decades has created the potential for improving the protective potency against these diseases. Genetic and subunit vaccines are two major categories of these emerging vaccines. Owing to their nature, they rely heavily on delivery systems with various functions, such as effective cargo protection, immunogenicity enhancement, targeted delivery, sustained release of antigens, selective activation of humoral and/or cellular immune responses against specific antigens, and reduced adverse effects. Therefore, vaccine delivery systems may significantly affect the final outcome of genetic and other novel vaccines and are vital for their development. This review introduces these studies based on their research emphasis on functional design or administration route optimization, presents recent progress, and discusses features of new vaccine delivery systems, providing an overview of this field.

Nanocomposite hydrogels for biomedical applications

Nanomaterials' unique structures at the nanometer level determine their incredible functions, and based on this, they can be widely used in the field of nanomedicine. However, nanomaterials do possess disadvantages that cannot be ignored, such as burst release, rapid elimination, and poor bioadhesion. Hydrogels are scaffolds with three-dimensional structures, and they exhibit good biocompatibility and drug release capacity. Hydrogels are also associated with disadvantages for biomedical applications such as poor anti-tumor capability, weak bioimaging capability, limited responsiveness, and so on. Incorporating nanomaterials into the 3D hydrogel network through physical or chemical covalent action may be an effective method to avoid their disadvantages. In nanocomposite hydrogel systems, multifunctional nanomaterials often work as the function core, giving the hydrogels a variety of properties (such as photo-thermal conversion, magnetothermal conversion, conductivity, targeting tumor, etc.). While, hydrogels can effectively improve the retention effect of nanomaterials and make the nanoparticles have good plasticity to adapt to various biomedical applications (such as various biosensors). Nanocomposite hydrogel systems have broad application prospects in biomedicine. In this review, we comprehensively summarize and discuss the most recent advances of nanomaterials composite hydrogels in biomedicine, including drug and cell delivery, cancer treatment, tissue regeneration, biosensing, and bioimaging, and we also briefly discussed the current situation of their commoditization in biomedicine.

Microneedle-based technology for cell therapy: current status and future directions

With the growing technological innovations in medical treatments, cell-based therapies hold great potential as efficient tools against various previously incurable diseases by restoring or altering the function of certain sets of cells. Along this line, an essential factor to determine the success of cell therapy is the choice of cell delivery strategy. In recent years, a novel trend is blooming in the application of microneedle systems, which are based on the miniaturization of multiple needles within a patch to the micrometer dimensions, aimed at the delivery of therapeutic cells to the target site with high efficiency and in a minimally invasive manner. This review aims to demonstrate the advantages of exploiting microneedle-based technology as a new tool for cell therapy. The advancements of microneedle-based strategies for cell delivery are summarized in terms of two categories: cell-free and cell-loaded microneedle systems. The majority of research on microneedle-based cell therapy has shown promising results for tissue regeneration, cancer immunotherapy, skin immune monitoring and targeted cell delivery. Finally, current challenges and future perspectives toward the development and application of microneedles for cell therapy are also discussed.

Virus Detection: From State-of-the-Art Laboratories to Smartphone-Based Point-of-Care Testing

Infectious virus outbreaks pose a significant challenge to public healthcare systems. Early and accurate virus diagnosis is critical to prevent the spread of the virus, especially when no specific vaccine or effective medicine is available. In clinics, the most commonly used viral detection methods are molecular techniques that involve the measurement of nucleic acids or proteins biomarkers. However, most clinic-based methods require complex infrastructure and expensive equipment, which are not suitable for low-resource settings. Over the past years, smartphone-based point-of-care testing (POCT) has rapidly emerged as a potential alternative to laboratory-based clinical diagnosis. This review summarizes the latest development of virus detection. First, laboratory-based and POCT-based viral diagnostic techniques are compared, both of which rely on immunosensing and nucleic acid detection. Then, various smartphone-based POCT diagnostic techniques, including optical biosensors, electrochemical biosensors, and other types of biosensors are discussed. Moreover, this review covers the development of smartphone-based POCT diagnostics for various viruses including COVID-19, Ebola, influenza, Zika, HIV, et al. Finally, the prospects and challenges of smartphone-based POCT diagnostics are discussed. It is believed that this review will aid researchers better understand the current challenges and prospects for achieving the ultimate goal of containing disease-causing viruses worldwide.

Polysaccharide-Based Transdermal Drug Delivery

Materials derived from natural plants and animals have great potential for transdermal drug delivery. Polysaccharides are widely derived from marine, herbal, and microbial sources. Compared with synthetic polymers, polysaccharides have the advantages of non-toxicity and biodegradability, ease of modification, biocompatibility, targeting, and antibacterial properties. Currently, polysaccharide-based transdermal drug delivery vehicles, such as hydrogel, film, microneedle (MN), and tissue scaffolds are being developed. The addition of polysaccharides allows these vehicles to exhibit better-swelling properties, mechanical strength, tensile strength, etc. Due to the stratum corneum’s resistance, the transdermal drug delivery system cannot deliver drugs as efficiently as desired. The charge and hydration of polysaccharides allow them to react with the skin and promote drug penetration. In addition, polysaccharide-based nanotechnology enhances drug utilization efficiency. Various diseases are currently treated by polysaccharide-based transdermal drug delivery devices and exhibit promising futures. The most current knowledge on these excellent materials will be thoroughly discussed by reviewing polysaccharide-based transdermal drug delivery strategies.

Recent Progress in Microneedles-Mediated Diagnosis, Therapy, and Theranostic Systems

Theranostic system combined diagnostic and therapeutic modalities is critical for the real-time monitoring of disease-related biomarkers and personalized therapy. Microneedles, as a multifunctional platform, are promising for transdermal diagnostics and drug delivery. They have shown attractive properties including painless skin penetration, easy self-administration, prominent therapeutic effects, and good biosafety. Herein, an overview of the microneedles-based diagnosis, therapies, and theranostic systems is given. Four microneedles-based detection methods are concluded based on the sensing mechanism: i) electrochemistry, ii) fluorometric, iii) colorimetric, and iv) Raman methods. Additionally, robust microneedles are suitable for implantable drug delivery. Microneedles-assisted transdermal drug delivery can be primarily classified as passive, active, and responsive drug release, based on the release mechanisms. Microneedles-assisted oral and implantable drug delivery mechanisms are also presented in this review. Furthermore, the key frontier developments in microneedles-mediated theranostic systems as the major selling points are emphasized in this review. These systems are classified into open-loop and closed-loop theranostic systems based on the indirectness and directness of feedback between the transdermal diagnosis and therapy, respectively. Finally, conclusions and future perspectives for next-generation microneedles-mediated theranostic systems are also discussed. Taken together, microneedle-based systems are promising as the new avenue for diagnosis, therapy, and disease-specific closed-loop theranostic applications.

A Sample and Detection Microneedle Patch for Psoriasis MicroRNA Biomarker Analysis in Interstitial Fluid

Skin interstitial fluid (ISF) containing a great variety of molecular biomarkers derived from cells and subcutaneous blood capillaries has recently emerged as a clinically potential component for early diagnosis of a wide range of diseases; however, the minimally invasive sampling and detection of cell-free biomarkers in ISF is still a key challenge. Herein, we developed microneedles (MNs) that consist of gelatin methacryloyl (GelMA) and graphene oxide (GO) for the enrichment and sensitive detection of multiple microRNA (miRNA) biomarkers from skin ISF. The GO-GelMA MNs exhibited robust mechanical properties, fast sampling kinetics, and large swelling capacity, which enabled collecting ISF volume high to 21.34 μL in 30 min, facilitating effective miRNA analysis. It preliminarily realized the sensitive detection of three types of psoriasis-related miRNAs biomarkers either on the patch itself or in solution after release from the hydrogel by combining catalytic hairpin assembly signal amplification reaction. The automated and minimally invasive ISF miRNA detection technology of GO-GelMA MNs has great potential to monitor cell-free clinically informative biomarkers for personalized diagnosis and prognosis.

Microfluidic Surgery in Single Cells and Multicellular Systems

Microscale surgery on single cells and small organisms has enabled major advances in fundamental biology and in engineering biological systems. Examples of applications range from wound healing and regeneration studies to the generation of hybridoma to produce monoclonal antibodies. Even today, these surgical operations are often performed manually, but they are labor intensive and lack reproducibility. Microfluidics has emerged as a powerful technology to control and manipulate cells and multicellular systems at the micro- and nanoscale with high precision. Here, we review the physical and chemical mechanisms of microscale surgery and the corresponding design principles, applications, and implementations in microfluidic systems. We consider four types of surgical operations: (1) sectioning, which splits a biological entity into multiple parts, (2) ablation, which destroys part of an entity, (3) biopsy, which extracts materials from within a living cell, and (4) fusion, which joins multiple entities into one. For each type of surgery, we summarize the motivating applications and the microfluidic devices developed. Throughout this review, we highlight existing challenges and opportunities. We hope that this review will inspire scientists and engineers to continue to explore and improve microfluidic surgical methods.

Minimally invasive skin sampling and transcriptome analysis using microneedles for skin type biomarker research

BACKGROUND

Minimally invasive skin sampling is used in various fields. In this study, we examined whether it was possible to obtain skin specimens using biocompatible microneedles composed of sodium hyaluronate and performed transcriptome analysis.

MATERIALS AND METHODS

Thirty-three subjects with different skin conditions, such as skin aging, skin hydration, skin pigmentation, oily skin and sensitive skin, were recruited. Skin types were evaluated based on age, non-invasive measurement devices, 10% lactic acid stinging test and visual assessment; the skin specimens were sampled from the face using microneedles. Total RNA was extracted, and microarray was performed. Correlations between various biomarkers and skin condition parameters were analysed.

RESULTS

Several skin-type biomarkers are correlated with age, non-invasive device measurements, LAST score and visual assessment of acne lesions. Representatively, COL1A1 (Collagen type 1 alpha 1 chain), FN1 (Fibronectin 1) and PINK1 (PTEN-induced putative kinase protein 1) for skin aging, FLG (Filaggrin), KLF4 (Kruppel-like factor 4) and LOR (Loricrin) for skin hydration, GPNMB (Glycoprotein non-metastatic melanoma protein B), MLANA (Melan-A) and TYR (Tyrosinase) for skin pigmentation, IGF1 (insulin-like growth factor-1), MPZL3 (Myelin protein zero like 3) and AQP3 (Aquaporin 3) for oily skin and PGF (placental growth factor), CYR61 (cysteine-rich angiogenic inducer 61), RBP4 (retinol-binding protein 4), TAC1 (Tachykinin precursor 1), CAMP (Cathelicidin antimicrobial peptide), MMP9 (Matrix metallopeptidase 9), MMP3, MMP12 and CCR1 (C-C motif chemokine receptor 1) for sensitive skin.

CONCLUSION

Microneedle skin sampling is a new and minimally invasive option for transcriptome analysis of human skin and can be applied for diagnosis and treatment efficacy evaluation, as well as skin type classification.

Designing spatial and temporal control of vaccine responses

Vaccines are the key technology to combat existing and emerging infectious diseases. However, increasing the potency, quality and durability of the vaccine response remains a challenge. As our knowledge of the immune system deepens, it becomes clear that vaccine components must be in the right place at the right time to orchestrate a potent and durable response. Material platforms, such as nanoparticles, hydrogels and microneedles, can be engineered to spatially and temporally control the interactions of vaccine components with immune cells. Materials-based vaccination strategies can augment the immune response by improving innate immune cell activation, creating local inflammatory niches, targeting lymph node delivery and controlling the time frame of vaccine delivery, with the goal of inducing enhanced memory immunity to protect against future infections. In this Review, we highlight the biological mechanisms underlying strong humoral and cell-mediated immune responses and explore materials design strategies to manipulate and control these mechanisms.

Wearable chem-biosensing devices: from basic research to commercial market

Wearable chem-biosensors have been garnering tremendous interest due to the significant potential in tailored healthcare diagnostics and therapeutics. With the development of the medical diagnostics revolution, wearable chem-biosensors as a rapidly emerging wave allow individuals to perform on-demand detection and obtain the required in-depth information. In contrast to commercial wearables, which tend to be miniaturized for measuring physical activities, the recent progressive wearable chem-biosensing device have mainly focused on non-invasive or minimally invasive monitoring biomarkers at the molecular level. Wearables is a multidisciplinary subject, and chem-biosensing is one of the most significant technologies. In this review, the currently basic academic research of wearable chem-biosensing devices and its commercial transformation were summarized and highlighted. Moreover, some representative wearable products on the market for individual health managements are presented. Strategies for the identification and sensing of biomarkers are discussed to further promote the development of wearable chem-biosensing devices. We also shared the limitations and breakthroughs of the next generation of chemo-biosensor wearables, from home use to clinical diagnosis.

Micro and Nanoscale Technologies for Diagnosis of Viral Infections

Viral infection is one of the leading causes of mortality worldwide. The growth of globalization significantly increases the risk of virus spreading, making it a global threat to future public health. In particular, the ongoing coronavirus disease 2019 (COVID-19) pandemic outbreak emphasizes the importance of devices and methods for rapid, sensitive, and cost-effective diagnosis of viral infections in the early stages by which their quick and global spread can be controlled. Micro and nanoscale technologies have attracted tremendous attention in recent years for a variety of medical and biological applications, especially in developing diagnostic platforms for rapid and accurate detection of viral diseases. This review addresses advances of microneedles, microchip-based integrated platforms, and nano- and microparticles for sampling, sample processing, enrichment, amplification, and detection of viral particles and antigens related to the diagnosis of viral diseases. Additionally, methods for the fabrication of microchip-based devices and commercially used devices are described. Finally, challenges and prospects on the development of micro and nanotechnologies for the early diagnosis of viral diseases are highlighted.

Microneedles in Drug Delivery: Progress and Challenges

In recent years, an innovative transdermal delivery technology has attracted great interest for its ability to distribute therapeutics and cosmeceuticals for several applications, including vaccines, drugs, and biomolecules for skin-related problems. The advantages of microneedle patch technology have been extensively evaluated in the latest literature; hence, the academic publications in this area are rising exponentially. Like all new technologies, the microneedle patch application has great potential but is not without limitations. In this review, we will discuss the possible limitations by highlighting the areas where a great deal of improvements are required. Emphasising these concerns early on should help scientists and technologists to address the matters in a timely fashion and to use their resources wisely.

Diagnostic and drug release systems based on microneedle arrays in breast cancer therapy

Microneedle arrays have recently received much attention as cancer detection and treatment platforms, because invasive injections and detection of the biopsy are not needed, and drug metabolism by the liver, as well as adverse effects of systemic drug administration, are diminished. Microneedles have been used for diagnosis, vaccination, and in targeted drug delivery of breast cancer. In this review, we summarize the recent progress in diagnosis and targeted drug delivery for breast cancer treatment, using microneedle arrays to deliver active molecules through the skin. The results not only suggest that health and well-being of patients are improved, but also that microneedle arrays can deliver anticancer compounds in a relatively noninvasive manner, based on body weight, breast tumor size, and circulation time of the drug. Moreover, microneedles could allow simultaneous loading of multiple drugs and enable controlled release, thus effectively optimizing or preventing drug-drug interactions. This review is designed to encourage the use of microneedles for diagnosis and treatment of breast cancer, by describing general properties of microneedles, materials used for construction, mechanism of action, and principal benefits. Ongoing challenges and future perspectives for the application of microneedle array systems in breast cancer detection and treatment are highlighted.

Advances in understanding the role of P-gp in doxorubicin resistance: Molecular pathways, therapeutic strategies, and prospects

P-glycoprotein (P-gp) is a drug efflux transporter that triggers doxorubicin (DOX) resistance. In this review, we highlight the molecular avenues regulating P-gp, such as Nrf2, HIF-1α, miRNAs, and long noncoding (lnc)RNAs, to reveal their participation in DOX resistance. These antitumor compounds and genetic tools synergistically reduce P-gp expression. Furthermore, ATP depletion impairs P-gp activity to enhance the antitumor activity of DOX. Nanoarchitectures, including liposomes, micelles, polymeric nanoparticles (NPs), and solid lipid nanocarriers, have been developed for the co-delivery of DOX with anticancer compounds and genes enhancing DOX cytotoxicity. Surface modification of nanocarriers, for instance with hyaluronic acid (HA), can promote selectivity toward cancer cells. We discuss these aspects with a focus on P-gp expression and activity.

Engineering Therapeutic Strategies in Cancer Immunotherapy via Exogenous Delivery of Toll-like Receptor Agonists

As a currently spotlighted method for cancer treatment, cancer immunotherapy has made a lot of progress in recent years. Among tremendous cancer immunotherapy boosters available nowadays, Toll-like receptor (TLR) agonists were specifically selected, because of their effective activation of innate and adaptive immune cells, such as dendritic cells (DCs), T cells, and macrophages. TLR agonists can activate signaling pathways of DCs to express CD80 and CD86 molecules, and secrete various cytokines and chemokines. The maturation of DCs stimulates naïve T cells to differentiate into functional cells, and induces B cell activation. Although TLR agonists have anti-tumor ability by activating the immune system of the host, their drawbacks, which include poor efficiency and remarkably short retention time in the body, must be overcome. In this review, we classify and summarize the recently reported delivery strategies using (1) exogenous TLR agonists to maintain the biological and physiological signaling activities of cargo agonists, (2) usage of multiple TLR agonists for synergistic immune responses, and (3) co-delivery using the combination with other immunomodulators or stimulants. In contrast to naked TLR agonists, these exogenous TLR delivery strategies successfully facilitated immune responses and subsequently mediated anti-tumor efficacy.