Localized Delivery of Theranostic Nanoparticles and High-Energy Photons using Microneedles-on-Bioelectronics

Microneedle patch capable of dual drug release for drug delivery to brain tumors

Primary brain tumors are mostly managed using surgical resection procedures. Nevertheless, in certain cases, a thin layer of tumors may remain outside of the resection process due to the possibility of permanent injury; these residual tumors expose patients to the risk of tumor recurrence. This study has introduced the use of microneedle patches implanted after surgery with a dual-release mechanism for the administration of doxorubicin. The proposed patches possess the capability to administer drugs directly to the residual tumors and initiate chemotherapy immediately following surgical procedures. Three-dimensional simulation of drug delivery to residual tumors in the brain has been performed based on a finite element method. The impact of four important parameters on drug delivery has been investigated, involving the fraction of drug released in the burst phase, the density of microneedles on the patch, the length of microneedles, and the microvascular density of the tumor. The simulation findings indicate that lowering the fraction of drug released in the initial burst phase reduces the maximum average concentration, but the sustained release that continues for a longer period, increasing the bioavailability of free drug. However, the area under curve (AUC) for different release rates remains unchanged due to the fact that an identical dose of drug is supplied in each instance. By increasing the density of microneedles on the patch, concentration accumulation is provided over an extensive region of tumor, which in turn induces more cancer cell death. A comparative analysis of various lengths reveals that longer microneedles facilitate profound penetration into the tumor layers and present better therapeutic response due to extensive area of the tumor which is exposure to chemotherapeutic drugs. Furthermore, high microvascular density, as a characteristic of the tumor microenvironment, is shown to have a significant impact on the blood microvessels drainage of drugs and consequently lower therapeutic response outcome. Our approach offers a computational framework for creating localized drug delivery systems and addressing the challenges related to residual brain tumors.

Microneedle-based nanodrugs for tumor immunotherapy

Microneedles have emerged as a promising and effective method for delivering therapeutic drugs and immunobiologics to treat various diseases. It is widely recognized that immune therapy has limited efficacy in solid tumors due to physical barriers and the immunosuppressive tumor microenvironment. Microneedle-based nanodrugs (NDMNs) offer a novel approach to overcome these limitations. These tiny needles are designed to load a variety of inorganic and organic nanoparticles, antigen vaccines, gene drugs, oncolytic viruses, and more. Utilizing microneedle arrays, NDMNs can effectively penetrate the skin barrier, delivering drugs precisely to the tumor site or immunoactive regions within the skin. Additionally, by designing and optimizing the microneedle structure, shape, and functionality, NDMNs enable precise drug release and efficient penetration, thereby enhancing the efficacy of tumor immunotherapy. In this review, we comprehensively discuss the pivotal role of NDMNs in cancer immunotherapy, summarizing innovative microneedle design strategies, mechanisms of immune activation, and delivery strategies of various nanodrugs. Furthermore, we explore the current clinical realities, limitations, and future prospects of NDMNs in tumor immunotherapy.

Microneedles as a Promising Technology for Disease Monitoring and Drug Delivery: A Review

The delivery of molecules, such as DNA, RNA, peptides, and certain hydrophilic drugs, across the epidermal barrier poses a significant obstacle. Microneedle technology has emerged as a prominent area of focus in biomedical research because of its ability to deliver a wide range of biomolecules, vaccines, medicines, and other substances through the skin. Microneedles (MNs) form microchannels by disrupting the skin's structure, which compromises its barrier function, and facilitating the easy penetration of drugs into the skin. These devices enhance the administration of many therapeutic substances to the skin, enhancing their stability. Transcutaneous delivery of medications using a microneedle patch offers advantages over conventional drug administration methods. Microneedles containing active substances can be stimulated by different internal and external factors to result in the regulated release of the substances. To achieve efficient drug administration to the desired location, it is necessary to consider the design of needles with appropriate optimized characteristics. The choice of materials for developing and manufacturing these devices is vital in determining the pharmacodynamics and pharmacokinetics of drug delivery. This article provides the most recent update and overview of the numerous microneedle systems that utilize different activators to stimulate the release of active components from the microneedles. Further, it discusses the materials utilized for producing microneedles and the design strategies important in managing the release of drugs. An explanation of the commonly employed fabrication techniques in biomedical applications and electronics, particularly for integrated microneedle drug delivery systems, is discussed. To successfully implement microneedle technology in clinical settings, it is essential to comprehensively assess several factors, such as biocompatibility, drug stability, safety, and production cost. Finally, an in-depth review of these criteria and the difficulties and potential future direction of microneedles in delivering drugs and monitoring diseases is explored.

Engineering the Functional Expansion of Microneedles

Microneedles (MNs), composed of an array of micro-sized needles and a supporting base, have transcended their initial use to replace hypodermic needles in drug delivery and fluid collection, advancing toward multifunctional platforms. In this review, four major areas are summarized in interdisciplinary engineering approaches combined with MNs technology. First, electronics engineering, the most extensively researched field, enables applications in biomonitoring, electrical stimulation, and closed-loop theranostics through the generation, transmission, and transformation of electrical signals. Second, in electromagnetic engineering, the responsiveness of electromagnetic induction offers prospects for remote and programmable therapeutic applications. Third, photonic engineering endows MNs with novel functionalities, such as waveguiding and photonic manipulation to enhance optical therapeutic capabilities and facilitate the visualization of disease progression and treatment processes. Lastly, it reviewed the role of mechanical engineering in conferring shape adaptability and programmable motion features necessary for various MNs applications. This review focuses on the functionalities that emerge from the intersection of MNs with complementary engineering technologies, aiming to inspire further research and innovation in microneedle technology for biomedical applications.

Local administration of irinotecan using an implantable drug delivery device stops high-grade glioma tumor recurrence in a glioblastoma tumor model

The treatment for Glioblastoma is limited due to the presence of the blood brain barrier, which restricts the entry of chemotherapeutic drugs into the brain. Local delivery into the tumor resection margin has the potential to improve efficacy of chemotherapy. We developed a safe and clinically translatable irinotecan implant for local delivery to increase its efficacy while minimizing systemic side effects. Irinotecan-loaded implants were manufactured using hot melt extrusion, gamma sterilized at 25 kGy, and characterized for their irinotecan content, release, and drug diffusion. Their therapeutic efficacy was evaluated in a patient-derived xenograft mouse resection model of glioblastoma. Their safety and translatability were evaluated using histological analysis of brain tissue and serum chemistry analysis. Implants containing 30% and 40% w/w irinotecan were manufactured without plasticizer. The 30% and 40% implants showed moderate local toxicity up to 2- and 6-day post-implantation. Histopathology of the implantation site showed signs of necrosis at days 45 and 14 for the 30% and 40% implants. Hematological analysis and clinical chemistry showed no signs of serious systemic toxicity for either implant. The 30% implants had an 80% survival at day 148, with no sign of tumor recurrence. Gamma sterilization and 12-month storage had no impact on the integrity of the 30% implants. This study demonstrates that the 30% implants are a promising novel treatment for glioblastoma that could be quickly translated into the clinic.

Implantable Microneedle-Mediated Eradication of Postoperative Tumor Foci Mitigates Glioblastoma Relapse

Glioblastoma multiforme (GBM) remains incurable despite multimodal treatments after surgical debulking. Almost all patients with GBM relapse within a narrow margin (2-3 cm) of the initial resected lesion due to the unreachable residual cancerous cells. Here, a completely biodegradable microneedle for surgical cavity delivery glioblastoma-associated macrophages (GAMs)-activating immune nano-stimulator that mitigates glioblastoma relapse is reported. The residual tumor lesion-directed biocompatible microneedle releases the nano-stimulator and toll-like receptor 9 agonist in a controlled manner until the microneedles completely degrade over 1 week, efferently induce in situ phonotypic shifting of GAMs from anti- to pro-inflammatory and the tumor recurrence is obviously inhibited. The implantable microneedles offer a significant improvement over conventional transdermal ones, as they are 100% degradable, ensuring safe application within surgical cavities. It is also revealed that the T cells are recruited to the tumor niche as the GAMs initiate anti-tumor response and eradicate residual GBM cells. Taken together, this work provides a potential strategy for immunomodulating the postoperative tumor niche to mitigate tumor relapse in GBM patients, which may have broad applications in other malignancies with surgical intervention.

Soft bioelectronics for diagnostic and therapeutic applications in neurological diseases

Physical and chemical signals in the central nervous system yield crucial information that is clinically relevant under both physiological and pathological conditions. The emerging field of bioelectronics focuses on the monitoring and manipulation of neurophysiological signals with high spatiotemporal resolution and minimal invasiveness. Significant advances have been realized through innovations in materials and structural design, which have markedly enhanced mechanical and electrical properties, biocompatibility, and overall device performance. The diagnostic and therapeutic potential of soft bioelectronics has been corroborated across a diverse array of pre-clinical settings. This review summarizes recent studies that underscore the developments and applications of soft bioelectronics in neurological disorders, including neuromonitoring, neuromodulation, tumor treatment, and biosensing. Limitations and outlooks of soft devices are also discussed in terms of power supply, wireless control, biocompatibility, and the integration of artificial intelligence. This review highlights the potential of soft bioelectronics as a future platform to promote deciphering brain functions and clinical outcomes of neurological diseases.

Soft Bioelectronics for Neuroengineering: New Horizons in the Treatment of Brain Tumor and Epilepsy

Soft bioelectronic technologies for neuroengineering have shown remarkable progress, which include novel soft material technologies and device design strategies. Such technological advances that are initiated from fundamental brain science are applied to clinical neuroscience and provided meaningful promises for significant improvement in the diagnosis efficiency and therapeutic efficacy of various brain diseases recently. System-level integration strategies in consideration of specific disease circumstances can enhance treatment effects further. Here, recent advances in soft implantable bioelectronics for neuroengineering, focusing on materials and device designs optimized for the treatment of intracranial disease environments, are reviewed. Various types of soft bioelectronics for neuroengineering are categorized and exemplified first, and then details for the sensing and stimulating device components are explained. Next, application examples of soft implantable bioelectronics to clinical neuroscience, particularly focusing on the treatment of brain tumor and epilepsy are reviewed. Finally, an ideal system of soft intracranial bioelectronics such as closed-loop-type fully-integrated systems is presented, and the remaining challenges for their clinical translation are discussed.

Advancements in manganese complex-based MRI agents: Innovations, design strategies, and future directions

This review focuses on the advancements in manganese (Mn) complex-based magnetic resonance imaging (MRI) agents for imaging different diseases. Here we emphasize the unique redox properties of Mn to deliver innovative MRI contrast agents, including small molecules, nanoparticles (NPs), metal-organic frameworks (MOFs), and polymer hybrids. Aspects of their rational design have been discussed, including size dependence, morphology tuning, surface property enhancement, etc., while also discussing the existing challenges and potential solutions. The present work will inspire and motivate scientists to emphasize MRI-guided applications and bring clinical success in the coming years.

Advances of Smart Stimulus-Responsive Microneedles in Cancer Treatment

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

Softening implantable bioelectronics: Material designs, applications, and future directions

Implantable bioelectronics, integrated directly within the body, represent a potent biomedical solution for monitoring and treating a range of medical conditions, including chronic diseases, neural disorders, and cardiac conditions, through personalized medical interventions. Nevertheless, contemporary implantable bioelectronics rely heavily on rigid materials (e.g., inorganic materials and metals), leading to inflammatory responses and tissue damage due to a mechanical mismatch with biological tissues. Recently, soft electronics with mechanical properties comparable to those of biological tissues have been introduced to alleviate fatal immune responses and improve tissue conformity. Despite their myriad advantages, substantial challenges persist in surgical handling and precise positioning due to their high compliance. To surmount these obstacles, softening implantable bioelectronics has garnered significant attention as it embraces the benefits of both rigid and soft bioelectronics. These devices are rigid for easy standalone implantation, transitioning to a soft state in vivo in response to environmental stimuli, which effectively overcomes functional/biological problems inherent in the static mechanical properties of conventional implants. This article reviews recent research and development in softening materials and designs for implantable bioelectronics. Examples featuring tissue-penetrating and conformal softening devices highlight the promising potential of these approaches in biomedical applications. A concluding section delves into current challenges and outlines future directions for softening implantable device technologies, underscoring their pivotal role in propelling the evolution of next-generation bioelectronics.

Microneedle-mediated drug delivery for neurological diseases

Neurological disorders, including brain injury, brain tumors, and neurodegenerative diseases, rank as the second leading cause of death worldwide. Exploring effective new treatments for neurological disorders has long been a hot research issue in clinical practice. Recently, microneedles (MNs) have attracted much attention due to their designation as a "painless and non-invasive" novel transdermal delivery method, characterized by their biocompatibility and sustainability. The advantages of MNs open an avenue for potential therapeutic interventions targeting neurological disorders. This review presents a concise overview of progress in the field of MNs, with highlights on the application in the treatment of neurological disorders. Notably, trends in the development of MNs and future challenges are also discussed.

Nanocomposite hydrogel microneedles: a theranostic toolbox for personalized medicine

Due to the severity and high prevalence of cancer, as well as its complex pathological condition, new strategies for cancer treatment and diagnostics are required. As such, it is important to design a toolbox that integrates multiple functions on a single smart platform. Theranostic hydrogels offer an innovative and personalized method to tackle cancer while also considering patient comfort, thereby facilitating future implementation and translation to the clinic. In terms of theranostic systems used in cancer therapy, nanoparticles are widely used as diagnostic and therapeutic tools. Nanoparticles can achieve systemic circulation, evade host defenses, and deliver drugs and signaling agents at the targeted site, to diagnose and treat the disease at a cellular and molecular level. In this context, hydrogel microneedles have a high potential for multifunctional operation in medical devices, while avoiding the complications associated with the systemic delivery of therapeutics. Compared with oral administration and subcutaneous injection, microneedles offer advantages such as better patient compliance, faster onset of action, and improved permeability and efficacy. In addition, they comprise highly biocompatible polymers with excellent degradability and tunable properties. Nanoparticles and microneedles thus offer the possibility to expand the theranostic potential through combined synergistic use of their respective features. We review herein recent advances concerning processing methods and material requirements within the realm of hydrogel microneedles as theranostic platforms, various approaches toward cancer therapy, and the incorporation of nanoparticles for added functionality.

Self-powered triboelectric-responsive microneedles with controllable release of optogenetically engineered extracellular vesicles for intervertebral disc degeneration repair

Excessive exercise is an etiological factor of intervertebral disc degeneration (IVDD). Engineered extracellular vesicles (EVs) exhibit excellent therapeutic potential for disease-modifying treatments. Herein, we fabricate an exercise self-powered triboelectric-responsive microneedle (MN) assay with the sustainable release of optogenetically engineered EVs for IVDD repair. Mechanically, exercise promotes cytosolic DNA sensing-mediated inflammatory activation in senescent nucleus pulposus (NP) cells (the master cell population for IVD homeostasis maintenance), which accelerates IVDD. TREX1 serves as a crucial nuclease, and disassembly of TRAM1-TREX1 complex disrupts the subcellular localization of TREX1, triggering TREX1-dependent genomic DNA damage during NP cell senescence. Optogenetically engineered EVs deliver TRAM1 protein into senescent NP cells, which effectively reconstructs the elimination function of TREX1. Triboelectric nanogenerator (TENG) harvests mechanical energy and triggers the controllable release of engineered EVs. Notably, an optogenetically engineered EV-based targeting treatment strategy is used for the treatment of IVDD, showing promising clinical potential for the treatment of degeneration-associated disorders.

Advances in Hydrogels of Drug Delivery Systems for the Local Treatment of Brain Tumors

The management of brain tumors presents numerous challenges, despite the employment of multimodal therapies including surgical intervention, radiotherapy, chemotherapy, and immunotherapy. Owing to the distinct location of brain tumors and the presence of the blood-brain barrier (BBB), these tumors exhibit considerable heterogeneity and invasiveness at the histological level. Recent advancements in hydrogel research for the local treatment of brain tumors have sought to overcome the primary challenge of delivering therapeutics past the BBB, thereby ensuring efficient accumulation within brain tumor tissues. This article elaborates on various hydrogel-based delivery vectors, examining their efficacy in the local treatment of brain tumors. Additionally, it reviews the fundamental principles involved in designing intelligent hydrogels that can circumvent the BBB and penetrate larger tumor areas, thereby facilitating precise, controlled drug release. Hydrogel-based drug delivery systems (DDSs) are posited to offer a groundbreaking approach to addressing the challenges and limitations inherent in traditional oncological therapies, which are significantly impeded by the unique structural and pathological characteristics of brain tumors.

Soft Bioelectronics Using Nanomaterials and Nanostructures for Neuroengineering

The identification of neural networks for large areas and the regulation of neuronal activity at the single-neuron scale have garnered considerable attention in neuroscience. In addition, detecting biochemical molecules and electrically, optically, and chemically controlling neural functions are key research issues. However, conventional rigid and bulky bioelectronics face challenges for neural applications, including mechanical mismatch, unsatisfactory signal-to-noise ratio, and poor integration of multifunctional components, thereby degrading the sensing and modulation performance, long-term stability and biocompatibility, and diagnosis and therapy efficacy. Implantable bioelectronics have been developed to be mechanically compatible with the brain environment by adopting advanced geometric designs and utilizing intrinsically stretchable materials, but such advances have not been able to address all of the aforementioned challenges.Recently, the exploration of nanomaterial synthesis and nanoscale fabrication strategies has facilitated the design of unconventional soft bioelectronics with mechanical properties similar to those of neural tissues and submicrometer-scale resolution comparable to typical neuron sizes. The introduction of nanotechnology has provided bioelectronics with improved spatial resolution, selectivity, single neuron targeting, and even multifunctionality. As a result, this state-of-the-art nanotechnology has been integrated with bioelectronics in two main types, i.e., bioelectronics integrated with synthesized nanomaterials and bioelectronics with nanoscale structures. The functional nanomaterials can be synthesized and assembled to compose bioelectronics, allowing easy customization of their functionality to meet specific requirements. The unique nanoscale structures implemented with the bioelectronics could maximize the performance in terms of sensing and stimulation. Such soft nanobioelectronics have demonstrated their applicability for neuronal recording and modulation over a long period at the intracellular level and incorporation of multiple functions, such as electrical, optical, and chemical sensing and stimulation functions.In this Account, we will discuss the technical pathways in soft bioelectronics integrated with nanomaterials and implementing nanostructures for application to neuroengineering. We traced the historical development of bioelectronics from rigid and bulky structures to soft and deformable devices to conform to neuroengineering requirements. Recent approaches that introduced nanotechnology into neural devices enhanced the spatiotemporal resolution and endowed various device functions. These soft nanobioelectronic technologies are discussed in two categories: bioelectronics with synthesized nanomaterials and bioelectronics with nanoscale structures. We describe nanomaterial-integrated soft bioelectronics exhibiting various functionalities and modalities depending on the integrated nanomaterials. Meanwhile, soft bioelectronics with nanoscale structures are explained with their superior resolution and unique administration methods. We also exemplified the neural sensing and stimulation applications of soft nanobioelectronics across various modalities, showcasing their clinical applications in the treatment of neurological diseases, such as brain tumors, epilepsy, and Parkinson's disease. Finally, we discussed the challenges and direction of next-generation technologies.

Application of microneedling in photodynamic therapy: A systematic review

BACKGROUND

The application of photodynamic therapy (PDT) is pivotal in the management of diverse dermatologic conditions. Microneedling (MN) is a minimally invasive tool that is capable of inducing transient pores on the skin to facilitate transdermal drug delivery. Several studies have reported augmentation of PDT combined with MN. This systematic review analyzes the current studies on the efficacy and safety of MN-assisted PDT for skin diseases.

METHODS

The literature search using the PRISMA standard was completed through PubMed, Embase, Web of Science and CENTRAL from the establishment of the databases to November 2023. Two independent researchers finished the procedure.

RESULTS

A total of 12 articles and 413 subjects met our study criteria. This systematic review suggests that MN-assisted PDT can decrease the incubation time required for the photosensitizer and reduce skin lesions of actinic keratosis (AK) . The common side effect is pain and no serious adverse events were reported.

CONCLUSIONS

MN is an effective method to increase the transdermal delivery rate of photosensitizers. For different photosensitizers and disease, MN may show different clinical effects.

Bridging Smart Nanosystems with Clinically Relevant Models and Advanced Imaging for Precision Drug Delivery

Intracellular delivery of nano-drug-carriers (NDC) to specific cells, diseased regions, or solid tumors has entered the era of precision medicine that requires systematic knowledge of nano-biological interactions from multidisciplinary perspectives. To this end, this review first provides an overview of membrane-disruption methods such as electroporation, sonoporation, photoporation, microfluidic delivery, and microinjection with the merits of high-throughput and enhanced efficiency for in vitro NDC delivery. The impact of NDC characteristics including particle size, shape, charge, hydrophobicity, and elasticity on cellular uptake are elaborated and several types of NDC systems aiming for hierarchical targeting and delivery in vivo are reviewed. Emerging in vitro or ex vivo human/animal-derived pathophysiological models are further explored and highly recommended for use in NDC studies since they might mimic in vivo delivery features and fill the translational gaps from animals to humans. The exploration of modern microscopy techniques for precise nanoparticle (NP) tracking at the cellular, organ, and organismal levels informs the tailored development of NDCs for in vivo application and clinical translation. Overall, the review integrates the latest insights into smart nanosystem engineering, physiological models, imaging-based validation tools, all directed towards enhancing the precise and efficient intracellular delivery of NDCs.

Photothermal-Controllable Microneedles with Antitumor, Antioxidant, Angiogenic, and Chondrogenic Activities to Sequential Eliminate Tracheal Neoplasm and Reconstruct Tracheal Cartilage

The optimal treatment for tracheal tumors necessitates sequential tumor elimination and tracheal cartilage reconstruction. This study introduces an innovative inorganic nanosheet, MnO2 /PDA@Cu, comprising manganese dioxide (MnO2 ) loaded with copper ions (Cu) through in situ polymerization using polydopamine (PDA) as an intermediary. Additionally, a specialized methacrylic anhydride modified decellularized cartilage matrix (MDC) hydrogel with chondrogenic effects is developed by modifying a decellularized cartilage matrix with methacrylic anhydride. The MnO2 /PDA@Cu nanosheet is encapsulated within MDC-derived microneedles, creating a photothermal-controllable MnO2 /PDA@Cu-MDC microneedle. Effectiveness evaluation involved deep insertion of the MnO2 /PDA@Cu-MDC microneedle into tracheal orthotopic tumor in a murine model. Under 808 nm near-infrared irradiation, facilitated by PDA, the microneedle exhibited rapid overheating, efficiently eliminating tumors. PDA's photothermal effects triggered controlled MnO2 and Cu release. The MnO2 nanosheet acted as a potent inorganic nanoenzyme, scavenging reactive oxygen species for an antioxidant effect, while Cu facilitated angiogenesis. This intervention enhanced blood supply at the tumor excision site, promoting stem cell enrichment and nutrient provision. The MDC hydrogel played a pivotal role in creating a chondrogenic niche, fostering stem cells to secrete cartilaginous matrix. In conclusion, the MnO2 /PDA@Cu-MDC microneedle is a versatile platform with photothermal control, sequentially combining antitumor, antioxidant, pro-angiogenic, and chondrogenic activities to orchestrate precise tracheal tumor eradication and cartilage regeneration.

Advances in biomedical systems based on microneedles: design, fabrication, and application

Wearable devices have become prevalent in biomedical studies due to their convenient portability and potential utility in biomarker monitoring for healthcare. Accessing interstitial fluid (ISF) across the skin barrier, microneedle (MN) is a promising minimally invasive wearable technology for transdermal sensing and drug delivery. MN has the potential to overcome the limitations of conventional transdermal drug administration, making it another prospective mode of drug delivery after oral and injectable. Subsequently, combining MN with multiple sensing approaches has led to its extensive application to detect biomarkers in ISF. In this context, employing MN platforms and control schemes to merge diagnostic and therapeutic capabilities into theranostic systems will facilitate on-demand therapy and point-of-care diagnostics, paving the way for future MN technologies. A comprehensive analysis of the growing advances of microneedles in biomedical systems is presented in this review to summarize the latest studies for academics in the field and to offer for reference the issues that need to be addressed in MN application for healthcare. Covering an array of novel studies, we discuss the following main topics: classification of microneedles in the biomedical field, considerations of MN design, current applications of microneedles in diagnosis and therapy, and the regulatory landscape and prospects of microneedles for biomedical applications. This review sheds light on the significance of microneedle-based innovations, presenting an analysis of their potential implications and contributions to the community of wearable healthcare technologies. The review provides a comprehensive understanding of the field's current state and potential, making it a valuable resource for academics and clinicians seeking to harness the full potential of MN applications.

Recent Advances in Bioelectronics for Localized Drug Delivery

The last decade has witnessed remarkable advancements in bioelectronics, ushering in a new era of wearable and implantable devices for drug delivery. By utilizing miniaturized system design and/or flexible materials, bioelectronics illustrates ideal integration with target organs and tissues, making them ideal platforms for localized drug delivery. Furthermore, the development of electrically assisted drug delivery systems has enhanced the efficiency and safety of therapeutic administration, particularly for the macromolecules that encounter additional challenges in penetrating biological barriers. In this review, a concise overview of recent progress in bioelectronic devices for in vivo localized drug delivery, with highlights on the latest trends in device design, working principles, and their corresponding functionalities, is provided. The reported systems based on their targeted delivery locations as wearable systems, ingestible systems, and implantable systems are categorized. Each category is introduced in detail by highlighting the special requirements for devices and the corresponding solutions. The remaining challenges in this field and future directions are also discussed.

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.

Polysaccharide-based tumor microenvironment-responsive drug delivery systems for cancer therapy

The biochemical indicators of tumor microenvironment (TME) that are different from normal tissues provide the possibility for constructing intelligent drug delivery systems (DDSs). Polysaccharides with good biocompatibility, biodegradability, and unique biological properties are ideal materials for constructing DDSs. Nanogels, micelles, organic-inorganic nanocomposites, hydrogels, and microneedles (MNs) are common polysaccharide-based DDSs. Polysaccharide-based DDSs enable precise control of drug delivery and release processes by incorporating TME-specific biochemical indicators. The classification and design strategies of polysaccharide-based TME-responsive DDSs are comprehensively reviewed. The advantages and challenges of current polysaccharide-based DDSs are summarized and the future directions of development are foreseen. The polysaccharide-based TME-responsive DDSs are expected to provide new strategies and solutions for cancer therapy and make important contributions to the realization of precision medicine.

Soft Bioelectronics for Therapeutics

Soft bioelectronics play an increasingly crucial role in high-precision therapeutics due to their softness, biocompatibility, clinical accuracy, long-term stability, and patient-friendliness. In this review, we provide a comprehensive overview of the latest representative therapeutic applications of advanced soft bioelectronics, ranging from wearable therapeutics for skin wounds, diabetes, ophthalmic diseases, muscle disorders, and other diseases to implantable therapeutics against complex diseases, such as cardiac arrhythmias, cancer, neurological diseases, and others. We also highlight key challenges and opportunities for future clinical translation and commercialization of soft therapeutic bioelectronics toward personalized medicine.

Laser-Induced Fabrication of Micro-Optics on Bioresorbable Calcium Phosphate Glass for Implantable Devices

In this study, a single-step nanosecond laser-induced generation of micro-optical features is demonstrated on an antibacterial bioresorbable Cu-doped calcium phosphate glass. The inverse Marangoni flow of the laser-generated melt is exploited for the fabrication of microlens arrays and diffraction gratings. The process is realized in a matter of few seconds and, by optimizing the laser parameters, micro-optical features with a smooth surface are obtained showing a good optical quality. The tunability of the microlens' dimensions is achieved by varying the laser power, allowing the obtaining of multi-focal microlenses that are of great interest for three-dimensional (3D) imaging. Furthermore, the microlens' shape can be tuned between hyperboloid and spherical. The fabricated microlenses exhibited good focusing and imaging performance and the variable focal lengths were measured experimentally, showing good agreement with the calculated values. The diffraction gratings obtained by this method showed the typical periodic pattern with a first-order efficiency of about 5.1%. Finally, the dissolution characteristics of the fabricated micropatterns were studied in a phosphate-buffered saline solution (PBS, pH = 7.4) demonstrating the bioresorbability of the micro-optical components. This study offers a new approach for the fabrication of micro-optics on bioresorbable glass, which could enable the manufacturing of new implantable optical sensing components for biomedical applications.

Long-Acting Therapeutic Delivery Systems for the Treatment of Gliomas

Despite the emergence of cutting-edge therapeutic strategies and tremendous progress in research, a complete cure of glioma remains elusive. The heterogenous nature of tumor, immunosuppressive state and presence of blood brain barrier are few of the major obstacles in this regard. Long-acting depot formulations such as injectables and implantables are gaining attention for drug delivery to brain owing to their ease in administration and ability to elute drug locally for extended durations in a controlled manner with minimal toxicity. Hybrid matrices fabricated by incorporating nanoparticulates within such systems help to enhance pharmaceutical advantages. Utilization of long-acting depots as monotherapy or in conjunction with existing strategies rendered significant survival benefits in many preclinical studies and some clinical trials. The discovery of novel targets, immunotherapeutic strategies and alternative drug administration routes are now coupled with several long-acting systems with an ultimate aim to enhance patient survival and prevent glioma recurrences.

Advanced Temporally-Spatially Precise Technologies for On-Demand Neurological Disorder Intervention

Temporal-spatial precision has attracted increasing attention for the clinical intervention of neurological disorders (NDs) to mitigate adverse effects of traditional treatments and achieve point-of-care medicine. Inspiring steps forward in this field have been witnessed in recent years, giving the credit to multi-discipline efforts from neurobiology, bioengineering, chemical materials, artificial intelligence, and so on, exhibiting valuable clinical translation potential. In this review, the latest progress in advanced temporally-spatially precise clinical intervention is highlighted, including localized parenchyma drug delivery, precise neuromodulation, as well as biological signal detection to trigger closed-loop control. Their clinical potential in both central and peripheral nervous systems is illustrated meticulously related to typical diseases. The challenges relative to biosafety and scaled production as well as their future perspectives are also discussed in detail. Notably, these intelligent temporally-spatially precision intervention systems could lead the frontier in the near future, demonstrating significant clinical value to support billions of patients plagued with NDs.

Penetrative and Sustained Drug Delivery Using Injectable Hydrogel Nanocomposites for Postsurgical Brain Tumor Treatment

Postsurgical treatment of glioblastoma multiforme (GBM) by systemic chemotherapy and radiotherapy is often inefficient. Tumor cells infiltrating deeply into the brain parenchyma are significant obstacles to the eradication of GBM. Here, we present a potential solution to this challenge by introducing an injectable thermoresponsive hydrogel nanocomposite. As a liquid solution that contains drug-loaded micelles and water-dispersible ferrimagnetic iron oxide nanocubes (wFIONs), the hydrogel nanocomposite is injected into the resected tumor site after surgery. It promptly gelates at body temperature to serve as a soft, deep intracortical drug reservoir. The drug-loaded micelles target residual GBM cells and deliver drugs with a minimum premature release. Alternating magnetic fields accelerate diffusion through heat generation from wFIONs, enabling penetrative drug delivery. Significantly suppressed tumor growth and improved survival rates are demonstrated in an orthotopic mouse GBM model. Our system proves the potential of the hydrogel nanocomposite platform for postsurgical GBM treatment.

3D-Printed Microinjection Needle Arrays via a Hybrid DLP-Direct Laser Writing Strategy

Microinjection protocols are ubiquitous throughout biomedical fields, with hollow microneedle arrays (MNAs) offering distinctive benefits in both research and clinical settings. Unfortunately, manufacturing-associated barriers remain a critical impediment to emerging applications that demand high-density arrays of hollow, high-aspect-ratio microneedles. To address such challenges, here, a hybrid additive manufacturing approach that combines digital light processing (DLP) 3D printing with "ex situ direct laser writing (esDLW)" is presented to enable new classes of MNAs for fluidic microinjections. Experimental results for esDLW-based 3D printing of arrays of high-aspect-ratio microneedles-with 30 μm inner diameters, 50 μm outer diameters, and 550 μm heights, and arrayed with 100 μm needle-to-needle spacing-directly onto DLP-printed capillaries reveal uncompromised fluidic integrity at the MNA-capillary interface during microfluidic cyclic burst-pressure testing for input pressures in excess of 250 kPa (n = 100 cycles). Ex vivo experiments perform using excised mouse brains reveal that the MNAs not only physically withstand penetration into and retraction from brain tissue but also yield effective and distributed microinjection of surrogate fluids and nanoparticle suspensions directly into the brains. In combination, the results suggest that the presented strategy for fabricating high-aspect-ratio, high-density, hollow MNAs could hold unique promise for biomedical microinjection applications.

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.

Multiscale Polymeric Materials for Advanced Lithium Battery Applications

Riding on the rapid growth in electric vehicles and the stationary energy storage market, high-energy-density lithium-ion batteries and next-generation rechargeable batteries (i.e., advanced batteries) have been long-accepted as essential building blocks for future technology reaching the specific energy density of 400 Wh kg^-1 at the cell-level. Such progress, mainly driven by the emerging electrode materials or electrolytes, necessitates the development of polymeric materials with advanced functionalities in the battery to address new challenges. Therefore, it is urgently required to understand the basic chemistry and essential research directions in polymeric materials and establish a library for the polymeric materials that enables the development of advanced batteries. Herein, based on indispensable polymeric materials in advanced high-energy-density lithium-ion, lithium-sulfur, lithium-metal, and dual-ion battery chemistry, the key research directions of polymeric materials for achieving high-energy-density and safety are summarized and design strategies for further improving performance are examined. Furthermore, the challenges of polymeric materials for advanced battery technologies are discussed.

Development of nanoparticle loaded microneedles for drug delivery to a brain tumour resection site

Systemic drug delivery to the central nervous system (CNS) has been historically impeded by the presence of the blood brain barrier rendering many therapies inefficacious to any cancer cells residing within the brain. Therefore, local drug delivery systems are being developed to overcome this shortfall. Here we have manufactured polymeric microneedle (MN) patches, which can be anchored within a resection cavity site following surgical removal of a tumour such as isocitrate dehydrogenase wild type glioblastoma (GBM). These MN patches have been loaded with polymer coated nanoparticles (NPs) containing cannabidiol (CBD) or olaparib (OLA) and applied to an in vitro brain simulant and ex vivo rat brain tissue to assess drug release and distance of penetration. MN patches loaded with methylene blue dye were placed into a cavity of 0.6 % agarose to simulate brain tissue. The results showed that clear channels were generated by the MNs and the dye spread laterally throughout the agarose. When loaded with CBD-NPs, the agarose showed a CBD concentration of 12.5 µg/g at 0.5 cm from the MN insertion site. Furthermore, high performance liquid chromatography of ex vivo brain tissue following CBD-NP/MN patch insertion showed successful delivery of 59.6 µg/g into the brain tissue. Similarly, OLA-NP loaded MN patches showed delivery of 5.2 µg/g OLA into agarose gel at 0.5 cm distance from the insertion site. Orbitrap secondary ion mass spectrometry (OrbiSIMS) analysis confirmed the presence of OLA and the MN patch at up to 6 mm away from the insertion site following its application to a rat brain hemisphere. This data has provided insight into the capabilities and versatility of MN patches for use in local brain drug delivery, giving promise for future research.

Revolutionizing Therapeutic Delivery with Microneedle Technology for Tumor Treatment

The tumor is an uncontrolled growth of tissue that can be localized (benign) or possesses the capability of metastasis (malignant). The conventional methods of tumor diagnosis, such as acupuncture, endoscopy, and histopathology, and treatment methods, such as injections, chemotherapy, surgery, and radiotherapy, are invasive, expensive, and pose severe safety and management issues for the patients. Microneedle technology is a recently developed approach for active transdermal drug delivery. It is minimally invasive, self-administrable, bypasses the first-pass effect, and effectively delivers chemotherapeutics and drugs at low doses, thus, overcoming the drawbacks of conventional delivery systems. This review provides an idea of the types, materials utilized in the fabrication, and techniques used for the preparation of microneedles (MNs), as well as their application in tumor diagnosis and treatment. Additionally, emphasis is given to the case studies related to MNs-assisted tumor therapy, such as photothermal therapy, gene therapy, photodynamic therapy, chemotherapy, immunotherapy, and various combination therapies. MNs also serve as a tool for diagnosis by the bio-sampling of blood and interstitial skin fluid, as well as biosensing various cancer biomarkers. The combined therapy and diagnostics provide theranostic MNs for enhanced and personalized tumor therapy. The limitations and prospects of MNs development are also discussed.

Electronically powered drug delivery devices: considerations and challenges

INTRODUCTION

Electronically powered drug delivery devices enable a controlled drug release route for a more convenient and painless way with reduced side effects. The current advances in microfabrication and microelectronics have facilitated miniaturization and intelligence with the integration of sensors and wireless communication modules. These devices have become an essential component of commercialized on-demand drug delivery.

AREAS COVERED

This review aims to provide a concise overview of current progress in electronically powered drug devices, focusing on delivery strategies, manufacturing techniques, and control circuit design with specific examples.

EXPERT OPINION

The application of electronically powered drug delivery systems is now considered a feasible therapeutic approach with improved drug release efficiency and increased patient comfort. It is anticipated that these technologies will gradually fulfill clinical needs and resolve commercialization challenges in the future. This review discusses the current advances in electronic drug delivery devices, especially focusing on designing strategies to achieve an effective drug release, as well as the perspectives and challenges for future applications in clinical therapy.

Local Drug Delivery Strategies for Glioblastoma Treatment

Glioblastoma multiforme (GBM) is a brain tumor notorious for its malignancy. The key reason for the limited efficacy of standard treatment is the high recurrence rate of GBM, even after surgical resection. Hence, intensive postsurgical chemical therapies, such as the systemic delivery of various drugs and/or drug combinations, are typically followed after surgery. However, overcoming the blood-brain barrier by systemic administration to efficiently deliver drugs to the brain tumor remains a daunting goal. Therefore, various local drug delivery methods showing potential for improved therapeutic efficacy have been proposed. In particular, the recent application of electronic devices for the controlled delivery of chemotherapy drugs to GBM tissue has attracted attention. We herein review the recent progress of local drug delivery strategies, including electronics-assisted strategies, at the research and commercial level. We also present a brief discussion of the unsolved challenges and future research direction of localized chemotherapy methods for GBM.

Biodegradable silicon nanoneedles for ocular drug delivery

Ocular drug delivery remains a grand challenge due to the complex structure of the eye. Here, we introduce a unique platform of ocular drug delivery through the integration of silicon nanoneedles with a tear-soluble contact lens. The silicon nanoneedles can penetrate into the cornea in a minimally invasive manner and then undergo gradual degradation over the course of months, enabling painless and long-term sustained delivery of ocular drugs. The tear-soluble contact lens can fit a variety of corneal sizes and then quickly dissolve in tear fluid within a minute, enabling an initial burst release of anti-inflammatory drugs. We demonstrated the utility of this platform in effectively treating a chronic ocular disease, such as corneal neovascularization, in a rabbit model without showing a notable side effect over current standard therapies. This platform could also be useful in treating other chronic ocular diseases.

Localised light delivery on melanoma cells using optical microneedles

Light-based therapy is an emerging treatment for skin cancer, which has received increased attention due to its drug-free and non-invasive approach. However, the limitation of current light therapy methods is the inability for light to penetrate the skin and reach deep lesions. As such, we have developed a polylactic acid (PLA) microneedles array as a novel light transmission platform to perform in vitro evaluation regarding the effect of light therapy on skin cancer. For the first time, we designed and fabricated a microneedle array system with a height fixation device that can be installed in a cell culture dish and an LED array for blue light irradiation. The effect of the blue light combined with the microneedles on cell apoptosis was evaluated using B16F10 melanoma cells and analyzed by Hoechst staining. Our results demonstrate that blue light can be transmitted by microneedles to skin cells and effectively affect cell viability.

Nanoparticle-assisted, image-guided laser interstitial thermal therapy for cancer treatment

Laser interstitial thermal therapy (LITT) guided by magnetic resonance imaging (MRI) is a new treatment option for patients with brain and non-central nervous system (non-CNS) tumors. MRI guidance allows for precise placement of optical fiber in the tumor, while MR thermometry provides real-time monitoring and assessment of thermal doses during the procedure. Despite promising clinical results, LITT complications relating to brain tumor procedures, such as hemorrhage, edema, seizures, and thermal injury to nearby healthy tissues, remain a significant concern. To address these complications, nanoparticles offer unique prospects for precise interstitial hyperthermia applications that increase heat transport within the tumor while reducing thermal impacts on neighboring healthy tissues. Furthermore, nanoparticles permit the co-delivery of therapeutic compounds that not only synergize with LITT, but can also improve overall effectiveness and safety. In addition, efficient heat-generating nanoparticles with unique optical properties can enhance LITT treatments through improved real-time imaging and thermal sensing. This review will focus on (1) types of inorganic and organic nanoparticles for LITT; (2) in vitro, in silico, and ex vivo studies that investigate nanoparticles' effect on light-tissue interactions; and (3) the role of nanoparticle formulations in advancing clinically relevant image-guided technologies for LITT. This article is categorized under: Therapeutic Approaches and Drug Discovery > Nanomedicine for Neurological Disease Implantable Materials and Surgical Technologies > Nanoscale Tools and Techniques in Surgery.

A Facile Low-Dose Photosensitizer-Incorporated Dissolving Microneedles-Based Composite System for Eliciting Antitumor Immunity and the Abscopal Effect

Nanomedicine-based photodynamic therapy (PDT) for melanoma treatment has attracted great attention. However, the complex design of polymer nanoparticles and high doses of photosensitizers used in intravenous injections (for sufficient accumulation of drugs in tumor lesions) pose a huge challenge to the commercialization and further clinical application. Herein, we fabricated the carrier-free nanoassemblies of a chlorin e6 (L-Ce6 NAs)-integrated fast-dissolving microneedles patch (L-Ce6 MNs) enriching only about 3 μg of Ce6 in the needle tips via a facile fabrication method. The L-Ce6 MNs had sufficient mechanical strength to penetrate the skin and facilitated the transportation of L-Ce6 NAs to a depth of 200-500 μm under the skin, thereby achieving efficient and accurate drug delivery to tumor lesions. In a xenograft mouse melanoma model, the L-Ce6 MNs-based PDT with low dose of Ce6 (0.12 mg/kg) exerted efficient ablation of the primary lesions in situ through reactive oxygen species (ROS) generation. More importantly, a significant abscopal effect was also elicited by activating immunogenic cell death (ICD) and releasing danger-associated molecular patterns (DAMPs), which in turn promoted dendritic cells (DCs) maturation and the subsequent antigen presentation, thereby facilitating the T-cell-mediated immune response without synergetic immunotherapies. Collectively, our findings indicate the facile, controllable, and fast-dissolving microneedles patch with a low dose of photosensitizers presented great therapeutic potential for enhanced photoimmunotherapy.

Soft Bioelectronics Based on Nanomaterials

Recent advances in nanostructured materials and unconventional device designs have transformed the bioelectronics from a rigid and bulky form into a soft and ultrathin form and brought enormous advantages to the bioelectronics. For example, mechanical deformability of the soft bioelectronics and thus its conformal contact onto soft curved organs such as brain, heart, and skin have allowed researchers to measure high-quality biosignals, deliver real-time feedback treatments, and lower long-term side-effects in vivo. Here, we review various materials, fabrication methods, and device strategies for flexible and stretchable electronics, especially focusing on soft biointegrated electronics using nanomaterials and their composites. First, we summarize top-down material processing and bottom-up synthesis methods of various nanomaterials. Next, we discuss state-of-the-art technologies for intrinsically stretchable nanocomposites composed of nanostructured materials incorporated in elastomers or hydrogels. We also briefly discuss unconventional device design strategies for soft bioelectronics. Then individual device components for soft bioelectronics, such as biosensing, data storage, display, therapeutic stimulation, and power supply devices, are introduced. Afterward, representative application examples of the soft bioelectronics are described. A brief summary with a discussion on remaining challenges concludes the review.

Flexible and biodegradable electronic implants for diagnosis and treatment of brain diseases

In the diagnosis and treatment of brain diseases, implantable devices have immense potential for intracranial sensing of brain activity and application of controlled therapy for providing feedback to the sensing. Flexible materials are preferred for implantable devices, as they can minimise implanted device-brain tissue mechanical mismatch. Moreover, biodegradable implantable devices can reduce potential immunological side-effects. Biodegradability also helps avoid the burdensome secondary surgery for retrieving the implanted device. In this study, we reviewed recent advancements related to the use of flexible and biodegradable type of implantable devices for the diagnosis and treatment of brain diseases. Representative cases of intracranial sensing and feedback therapy are introduced, and then a brief discussion concludes the review.

Recent advances in transdermal drug delivery systems: a review

Various non-invasive administrations have recently emerged as an alternative to conventional needle injections. A transdermal drug delivery system (TDDS) represents the most attractive method among these because of its low rejection rate, excellent ease of administration, and superb convenience and persistence among patients. TDDS could be applicable in not only pharmaceuticals but also in the skin care industry, including cosmetics. Because this method mainly involves local administration, it can prevent local buildup in drug concentration and nonspecific delivery to tissues not targeted by the drug. However, the physicochemical properties of the skin translate to multiple obstacles and restrictions in transdermal delivery, with numerous investigations conducted to overcome these bottlenecks. In this review, we describe the different types of available TDDS methods, along with a critical discussion of the specific advantages and disadvantages, characterization methods, and potential of each method. Progress in research on these alternative methods has established the high efficiency inherent to TDDS, which is expected to find applications in a wide range of fields.