Drug delivery systems based on intrinsically conducting polymers

Physical stimuli-responsive polymeric patches for healthcare

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

Soft Bioelectronics for Heart Monitoring

Cardiovascular diseases (CVDs) are a predominant global health concern, accounting for over 17.9 million deaths in 2019, representing approximately 32% of all global fatalities. In North America and Europe, over a million adults undergo cardiac surgeries annually. Despite the benefits, such surgeries pose risks and require precise postsurgery monitoring. However, during the postdischarge period, where monitoring infrastructures are limited, continuous monitoring of vital signals is hindered. In this area, the introduction of implantable electronics is altering medical practices by enabling real-time and out-of-hospital monitoring of physiological signals and biological information postsurgery. The multimodal implantable bioelectronic platforms have the capability of continuous heart sensing and stimulation, in both postsurgery and out-of-hospital settings. Furthermore, with the emergence of machine learning algorithms into healthcare devices, next-generation implantables will benefit artificial intelligence (AI) and connectivity with skin-interfaced electronics to provide more precise and user-specific results. This Review outlines recent advancements in implantable bioelectronics and their utilization in cardiovascular health monitoring, highlighting their transformative deployment in sensing and stimulation to the heart toward reaching truly personalized healthcare platforms compatible with the Sustainable Development Goal 3.4 of the WHO 2030 observatory roadmap. This Review also discusses the challenges and future prospects of these devices.

Conducting polymer hydrogels for biomedical application: Current status and outstanding challenges

Conducting polymer hydrogels (CPHs) are composite polymeric materials with unique properties that combine the electrical capabilities of conducting polymers (CPs) with the excellent mechanical properties and biocompatibility of traditional hydrogels. This review aims to highlight how the unique properties CPHs have from combining their two constituent materials are utilized within the biomedical field. First, the synthesis approaches and applications of non-CPH conductive hydrogels are discussed briefly, contrasting CPH-based systems. The synthesis routes of hydrogels, CPs, and CPHs are then discussed. This review also provides a comprehensive overview of the recent advancements and applications of CPHs in the biomedical field, encompassing their applications as biosensors, drug delivery scaffolds (DDSs), and tissue engineering platforms. Regarding their applications within tissue engineering, a comprehensive discussion of the usage of CPHs for skeletal muscle prosthetics and regeneration, cardiac regeneration, epithelial regeneration and wound healing, bone and cartilage regeneration, and neural prosthetics and regeneration is provided. Finally, critical challenges and future perspectives are also addressed, emphasizing the need for continued research; however, this fascinating class of materials holds promise within the vastly evolving field of biomedicine.

Dual electro-/pH-responsive nanoparticle/hydrogel system for controlled delivery of anticancer peptide

An electro-chemo-responsive carrier has been engineered for the controlled release of a highly hydrophilic anticancer peptide, CR(NMe)EKA (Cys-Arg- N-methyl-Glu-Lys-Ala). Remotely controlled on demand release of CR(NMe)EKA, loaded in electro-responsive poly(3,4-ethylenedioxythiophene) (PEDOT) nanoparticles, has been achieved by applying electrical stimuli consisting of constant positive (+0.50 V) or negative voltages (-0.50 V) at pre-defined time intervals. In addition, after loading CR(NMe)EKA/PEDOT nanoparticles into an injectable pH responsive hydrogel formed by phenylboronic acid grafted to chitosan (PBA-CS), the efficiency of the controlled peptide release has increased approximately by a factor of 2.6. The hydration ratio of such hydrogel is significantly lower in acidic environments than in neutral and basic media, which has been attributed to the dissociation of the boronate bonds between polymer chains. Hence, the electro-controlled peptide release from PBA-CS/CR(NMe)EKA/PEDOT hydrogels, in the acidic environment of tumors, combines the effects of the oxidation and reduction of PEDOT chains on the interactions with the peptide and the carrier, with the peptide concentration gradient at the interface between the collapsed hydrogel and the release medium. Furthermore, the peptide released by electro-stimulation preserved its bioactivity assessed by promoting human prostate cancer cells death. Overall, this work is a promising attempt to develop a carrier platform for small hydrophilic anticancer peptides, which delivery rationale is synergistically regulated by the electrical and pH responsiveness of the carrier.

Recent Progress in Implantable Drug Delivery Systems

In recent years, tremendous effort is devoted to developing platforms, such as implantable drug delivery systems (IDDSs), with temporally and spatially controlled drug release capabilities and improved adherence. IDDSs have multiple advantages: i) the timing and location of drug delivery can be controlled by patients using specific stimuli (light, sound, electricity, magnetism, etc.). Some intelligent "closed-loop" IDDS can even realize self-management without human participation. ii) IDDSs enable continuous and stable delivery of drugs over a long period (months to years) and iii) to administer drugs directly to the lesion, thereby helping reduce dosage and side effects. iv) IDDSs enable personalized drug delivery according to patient needs. The high demand for such systems has prompted scientists to make efforts to develop intelligent IDDS. In this review, several common stimulus-responsive mechanisms including endogenous (e.g., pH, reactive oxygen species, proteins, etc.) and exogenous stimuli (e.g., light, sound, electricity, magnetism, etc.), are given in detail. Besides, several types of IDDS reported in recent years are reviewed, including various stimulus-responsive systems based on the above mechanisms, radio frequency-controlled IDDS, "closed-loop" IDDS, self-powered IDDS, etc. Finally, the advantages and disadvantages of various IDDS, bottleneck problems, and possible solutions are analyzed to provide directions for subsequent research.

Biodegradable Conducting Polymer-Based Composites for Biomedical Applications-A Review

In recent years, researchers have increasingly directed their focus toward the biomedical field, driven by the goal of engineering polymer systems that possess a unique combination of both electrical conductivity and biodegradability. This convergence of properties holds significant promise, as it addresses a fundamental requirement for biomedical applications: compatibility with biological environments. These polymer systems are viewed as auspicious biomaterials, precisely because they meet this critical criterion. Beyond their biodegradability, these materials offer a range of advantageous characteristics. Their exceptional processability enables facile fabrication into various forms, and their chemical stability ensures reliability in diverse physiological conditions. Moreover, their low production costs make them economically viable options for large-scale applications. Notably, their intrinsic electrical conductivity further distinguishes them, opening up possibilities for applications that demand such functionality. As the focus of this review, a survey into the use of biodegradable conducting polymers in tissue engineering, biomedical implants, and antibacterial applications is conducted.

Remodeling of the Intra-Conduit Inflammatory Microenvironment to Improve Peripheral Nerve Regeneration with a Neuromechanical Matching Protein-Based Conduit

Peripheral nerve injury (PNI) remains a challenging area in regenerative medicine. Nerve guide conduit (NGC) transplantation is a common treatment for PNI, but the prognosis of NGC treatment is unsatisfactory due to 1) neuromechanical unmatching and 2) the intra-conduit inflammatory microenvironment (IME) resulting from Schwann cell pyroptosis and inflammatory-polarized macrophages. A neuromechanically matched NGC composed of regenerated silk fibroin (RSF) loaded with poly(3,4-ethylenedioxythiophene): poly(styrene sulfonate) (P:P) and dimethyl fumarate (DMF) are designed, which exhibits a matched elastic modulus (25.1 ± 3.5 MPa) for the peripheral nerve and the highest 80% elongation at break, better than most protein-based conduits. Moreover, the NGC can gradually regulate the intra-conduit IME by releasing DMF and monitoring sciatic nerve movements via piezoresistive sensing. The combination of NGC and electrical stimulation modulates the IME to support PNI regeneration by synergistically inhibiting Schwann cell pyroptosis and reducing inflammatory factor release, shifting macrophage polarization from the inflammatory M1 phenotype to the tissue regenerative M2 phenotype and resulting in functional recovery of neurons. In a rat sciatic nerve crush model, NGC promoted remyelination and functional and structural regeneration. Generally, the DMF/RSF/P:P conduit provides a new potential therapeutic approach to promote nerve repair in future clinical treatments.

Drug delivery via a 3D electro-swellable conjugated polymer hydrogel

Spatiotemporal controlled drug delivery minimizes side-effects and enables therapies that require specific dosing patterns. Conjugated polymers (CP) can be used for electrically controlled drug delivery; however so far, most demonstrations were limited to molecules up to 500 Da. Larger molecules could be incorporated only during the CP polymerization and thus limited to a single delivery. This work harnesses the record volume changes of a glycolated polythiophene p(g3T2) for controlled drug delivery. p(g3T2) undergoes reversible volumetric changes of up to 300% during electrochemical doping, forming pores in the nm-size range, resulting in a conducting hydrogel. p(g3T2)-coated 3D carbon sponges enable controlled loading and release of molecules spanning molecular weights of 800-6000 Da, from simple dyes up to the hormone insulin. Molecules are loaded as a combination of electrostatic interactions with the charged polymer backbone and physical entrapment in the porous matrix. Smaller molecules leak out of the polymer while larger ones could not be loaded effectively. Finally, this work shows the temporally patterned release of molecules with molecular weight of 1300 Da and multiple reloading and release cycles without affecting the on/off ratio.

Usefulness of the Distribution of Relaxation Time Method in Electroanalytical Systems: The Case of Voltammetric Ion-Selective Electrodes

Despite the distribution of relaxation time (DRT) method providing clear insights about processes that go unnoticed by traditional electrochemical impedance spectroscopy (EIS) analysis, it has not yet been adopted to solve electroanalytical systems. As an illustration case, we apply the DRT method to deconvolve EIS data from solid-state voltammetric ion-selective electrodes (ISEs). The main aim is to shed light on the underlying working mechanism across the different materials and interfaces, specifically, the doping of a conducting polymer when covered with a very thin (ca. 230 nm) permselective membrane. Although frequency-dependent AC measurements in EIS allow the separation of processes that contribute to the electrical signal, interpretation of the data is challenging. DRT may overcome this inconvenience by revealing a series of peaks corresponding to the predominant electrochemical processes, without any preknowledge on those. To demonstrate our hypothesis, we examine the conducting polymer poly(3-octylthiophene) (POT) linked to a membrane with sodium tetrakis[3,5-bis(trifluoromethyl)phenyl]borate (Na+TFPB-) as the cation exchanger, in which the lipophilic anionic part (TFPB-) is responsible for the POT doping when it gets electrochemically oxidized (POT+). The investigation of EIS data obtained under different conditions with the DRT method showed the occurrence of several processes. We have attributed two of these to two different conformational changes in the POT film in connection with p-type charge-transfer doping. Indeed, the kinetics is found to follow a Butler-Volmer behavior, with average charge transfers of 0.5 and 0.3 mol of electrons for each peak. Overall, we demonstrate the utility of the EIS-DRT tandem to separately study charge-transfer events that interconnect along the same (interfacial segmented) system, which cannot be reached by using classical electrochemical approaches. These kinds of insights are necessary for a more efficient design and high-level exploitation of voltammetric ISEs but also other electrochemical systems such as catalysts, batteries, and photovoltaic cells.

Roadmap on multifunctional materials for drug delivery

This Roadmap on drug delivery aims to cover some of the most recent advances in the field of materials for drug delivery systems (DDSs) and emphasizes the role that multifunctional materials play in advancing the performance of modern DDSs in the context of the most current challenges presented. The Roadmap is comprised of multiple sections, each of which introduces the status of the field, the current and future challenges faced, and a perspective of the required advances necessary for biomaterial science to tackle these challenges. It is our hope that this collective vision will contribute to the initiation of conversation and collaboration across all areas of multifunctional materials for DDSs. We stress that this article is not meant to be a fully comprehensive review but rather an up-to-date snapshot of different areas of research, with a minimal number of references that focus upon the very latest research developments.

Electroactive Polymers for On-Demand Drug Release

Conductive materials have played a significant role in advancing society into the digital era. Such materials are able to harness the power of electricity and are used to control many aspects of daily life. Conductive polymers (CPs) are an emerging group of polymers that possess metal-like conductivity yet retain desirable polymeric features, such as processability, mechanical properties, and biodegradability. Upon receiving an electrical stimulus, CPs can be tailored to achieve a number of responses, such as harvesting energy and stimulating tissue growth. The recent FDA approval of a CP-based material for a medical device has invigorated their research in healthcare. In drug delivery, CPs can act as electrical switches, drug release is achieved at a flick of a switch, thereby providing unprecedented control over drug release. In this review, recent developments in CP as electroactive polymers for voltage-stimuli responsive drug delivery systems are evaluated. The review demonstrates the distinct drug release profiles achieved by electroactive formulations, and both the precision and ease of stimuli response. This level of dynamism promises to yield "smart medicines" and warrants further research. The review concludes by providing an outlook on electroactive formulations in drug delivery and highlighting their integral roles in healthcare IoT.

The Alphabet of Nanostructured Polypyrrole

This review is devoted to polypyrrole and its morphology, which governs the electroactivity of the material. The macroscopic properties of the material are strictly relevant to microscopic ordering observed at the local level. During the synthesis, various (nano)morphologies can be produced. The formation of the ordered structure is dictated by the ability of the local forces and effects to induce restraints that help shape the structure. This review covers the aspects of morphology and roughness and their impact on the final properties of the modified electrode activity in selected applications.

Advancements in tailoring PEDOT: PSS properties for bioelectronic applications: A comprehensive review

In the field of bioelectronics, the demand for biocompatible, stable, and electroactive materials for functional biological interfaces, sensors, and stimulators, is drastically increasing. Conductive polymers (CPs) are synthetic materials, which are gaining increasing interest mainly due to their outstanding electrical, chemical, mechanical, and optical properties. Since its discovery in the late 1980s, the CP Poly(3,4-ethylenedioxythiophene):poly(styrene sulfonic acid) (PEDOT:PSS) has become extremely attractive, being considered as one of the most capable organic electrode materials for several bioelectronic applications in the field of tissue engineering and regenerative medicine. Main examples refer to thin, flexible films, electrodes, hydrogels, scaffolds, and biosensors. Within this context, the authors contend that PEDOT:PSS properties should be customized to encompass: i) biocompatibility, ii) conductivity, iii) stability in wet environment, iv) adhesion to the substrate, and, when necessary, v) (bio-)degradability. However, consolidating all these properties into a single functional solution is not always straightforward. Therefore, the objective of this review paper is to present various methods for acquiring and improving PEDOT:PSS properties, with the primary focus on ensuring its biocompatibility, and simultaneously addressing the other functional features. The last section highlights a collection of designated studies, with a particular emphasis on PEDOT:PSS/carbon filler composites due to their exceptional characteristics.

A di-electrophoretic simulation procedure of iron-oxide micro-particle drug attachment system for leukemia treatment using COMSOL software: a potential treatment reference for LMICs

Background

Leukemia encompasses various subtypes, each with unique characteristics and treatment approaches. The challenge lies in developing targeted therapies that can effectively address the specific genetic mutations or abnormalities associated with each subtype. Some leukemia cases may become resistant to existing treatments over time making them less susceptible to chemotherapy or other standard therapies.

Objective

Developing new treatment strategies to overcome resistance is an ongoing challenge particularly in Low and Middle Income Countries (LMICs). Computational studies using COMSOL software could provide an economical, fast and resourceful approach to the treatment of complicated cancers like leukemia.

Methods

Using COMSOL Multiphysics software, a continuous flow microfluidic device capable of delivering anti-leukemia drugs to early-stage leukemia cells has been computationally modeled using dielectrophoresis (DEP).

Results

The cell size difference enabled the micro-particle drug attachment to the leukemia cells using hydrodynamic focusing from the dielectrophoretic force. This point of care application produced a low voltage from numerically calculated electrical field and flow speed simulations.

Conclusion

Therefore, such a dielectrophoretic low voltage application model can be used as a computational treatment reference for early-stage leukemia cells with an approximate size of 5 μm.

Nanomaterial-based ophthalmic drug delivery

The low bioavailability and side effects of conventional drugs for eye disease necessitate the development of efficient drug delivery systems. Accompanying the developments of nanofabrication techniques, nanomaterials have been recognized as promising tools to overcome these challenges due to their flexible and programmable properties. Given the advances achieved in material science, a broad spectrum of functional nanomaterials capable of overcoming various ocular anterior and posterior segment barriers have been explored to satisfy the demands for ocular drug delivery. In this review, we first highlight the unique functions of nanomaterials suitable for carrying and transporting ocular drugs. Then, various functionalization strategies are emphasized to endow nanomaterials with superior performance in enhanced ophthalmic drug delivery. The rational design of several affecting factors is essential for ideal nanomaterial candidates and is depicted as well. Lastly, we introduce the current applications of nanomaterial-based delivery systems in the therapy of different ocular anterior and posterior segment diseases. The limitations of these delivery systems as well as potential solutions are also discussed. This work will inspire innovative design thinking for the development of nanotechnology-mediated strategies for advanced drug delivery and treatment toward ocular diseases.

Smart multi stimuli-responsive electrospun nanofibers for on-demand drug release

Here, we report poly(N-isopropylacrylamide-co-acrylic acid) (PNIPAm-co-AAc) microgel-loaded polycaprolactone (PCL) nanofibers as temperature-, pH- and electro-responsive materials. First, the PNIPAm-co-AAc microgels were prepared by precipitation polymerization and then electrospun with PCL. The morphology of the prepared materials, analysed by scanning electron microscopy, showed a narrow nanofiber distribution in the range of 500-800 nm, depending on microgel content. Refractometry measurements, performed at pH4 and 6.5, as well as in distilled water, indicated the thermo- and pH-responsive behaviour of the nanofibers between 31 and 34 °C. After being thoroughly characterized, the prepared nanofibers were loaded with crystal violet (CV) or gentamicin as model drugs. The application of a pulsed voltage led to a pronounced increase in drug release kinetics, which was also dependent on microgel content. In addition, long-term temperature- and pH-responsive release was demonstrated. Next, the prepared materials displayed switchable antibacterial activity against S. aureus and E. coli. Finally, cell compatibility tests showed that NIH 3T3 fibroblasts spread evenly over the nanofiber surface, confirming that the nanofibers serve as a favourable support for cell growth. Overall, the prepared nanofibers offer switchable drug release and appear to have considerable biomedical potential, particularly in wound healing.

Research progress of advanced microneedle drug delivery system and its application in biomedicine

Transdermal drug delivery is an effective way of drug delivery in addition to oral and intravenous administration. Among them, microneedle administration is a new type of subcutaneous drug delivery, which forms micron-level pores on the surface of the skin, making the drug enter the dermis through the cuticular layer of the skin in the least invasive way. This mode of drug delivery not only increases the permeation efficiency of transdermal drug delivery but also improves the bioavailability of drug delivery. At present, there are many kinds of research on microneedles, such as solid microneedles, hollow microneedles, soluble polymer microneedles, etc. However, some new microneedle drug delivery systems have been gradually developed and applied with the development of microneedle drug delivery technology, for meeting the more complex pathological environment. In this review, we focus on the principle, structure, and function of some new types of microneedles, such as stimulus-response microneedles, iontophoresis microneedles, and bionic microneedles. We summarize the effects of materials, geometry, and size on the properties of microneedles as well as their applications and potential developments in the field of biomedicine. We hope that this review can provide new ideas and help with the development of new microneedle drug delivery systems.

Electroresponsive and pH-Sensitive Hydrogel as Carrier for Controlled Chloramphenicol Release

Multiresponsive hydrogels, which are smart soft materials that respond to more than one external stimulus, have emerged as powerful tools for biomedical applications, such as drug delivery. Within this context and with the aim of eliminating the systematic administration of antibiotics, special attention is being paid to the development of systems for controlled delivery of antibiotic for topical treatment of bacterial infections. In this work, an electro-chemo responsive hydrogel able to release chloramphenicol (CAM), a broad spectrum antibiotic also used for anticancer therapy, is proposed. This has been prepared by grafting poly(acrylic acid) (PAA) to sodium alginate (Alg) and in situ encapsulation of poly(3,4-ethylenedioxythiophene) nanoparticles loaded with CAM (PEDOT/CAM NPs), which were obtained by emulsion polymerization. Although the response to electrical stimuli of PEDOT was the main control for the release of CAM from PEDOT/CAM NPs, the release by passive diffusion had a relatively important contribution. Conversely, the passive release of antibiotic from the whole engineered hydrogel system, Alg-g-PAA/PEDOT/CAM, was negligible, whereas significant release was achieved under electrostimulation in an acid environment. Bacterial tests and assays with cancer cells demonstrated that the biological activity of CAM remained after release by electrical stimulation. Notably, the successful dual-response of the developed hydrogel to electrical stimuli and pH changes evidence the great prospect of this smart material in the biomedical field, as a tool to fight against bacterial infections and to provide local cancer treatment.

Recent advances of polypyrrole conducting polymer film for biomedical application: Toward a viable platform for cell-microbial interactions

Polypyrrole (PPy) is one of the most studied conductive polymers due to its electrical conductivity and biological properties, which drive the possibility of numerous applications in the biomedical area. The physical-chemical features of PPy allow the manufacture of biocompatible devices, enhancing cell adhesion and proliferation. Furthermore, owing to the electrostatic interactions between the negatively charged bacterial cell wall and the positive charges in the polymer structure, PPy films can perform an effective antimicrobial activity. PPy is also frequently associated with biocompatible agents and antimicrobial compounds to improve the biological response. Thus, this comprehensive review appraised the available evidence regarding the PPy-based films deposited on metallic implanted devices for biomedical applications. We focus on understanding key concepts that could influence PPy attributes regarding antimicrobial effect and cell behavior under in vitro and in vivo settings. Furthermore, we unravel the several agents incorporated into the PPy film and strategies to improve its functionality. Our findings suggest that incorporating other elements into the PPy films, such as antimicrobial agents, biomolecules, and other biocompatible polymers, may improve the biological responses. Overall, the basic properties of PPy, when combined with other composites, electrostimulation techniques, or surface treatment methods, offer great potential in biocompatibility and/or antimicrobial activities. However, challenges in synthesis standardization and potential limitations such as low adhesion and mechanical strength of the film must be overcome to improve and broaden the application of PPy film in biomedical devices.

Soft Fiber Electronics Based on Semiconducting Polymer

Fibers, originating from nature and mastered by human, have woven their way throughout the entire history of human civilization. Recent developments in semiconducting polymer materials have further endowed fibers and textiles with various electronic functions, which are attractive in applications such as information interfacing, personalized medicine, and clean energy. Owing to their ability to be easily integrated into daily life, soft fiber electronics based on semiconducting polymers have gained popularity recently for wearable and implantable applications. Herein, we present a review of the previous and current progress in semiconducting polymer-based fiber electronics, particularly focusing on smart-wearable and implantable areas. First, we provide a brief overview of semiconducting polymers from the viewpoint of materials based on the basic concepts and functionality requirements of different devices. Then we analyze the existing applications and associated devices such as information interfaces, healthcare and medicine, and energy conversion and storage. The working principle and performance of semiconducting polymer-based fiber devices are summarized. Furthermore, we focus on the fabrication techniques of fiber devices. Based on the continuous fabrication of one-dimensional fiber and yarn, we introduce two- and three-dimensional fabric fabricating methods. Finally, we review challenges and relevant perspectives and potential solutions to address the related problems.

Polymeric Membranes for Biomedical Applications

Polymeric membranes are selective materials used in a wide range of applications that require separation processes, from water filtration and purification to industrial separations. Because of these materials' remarkable properties, namely, selectivity, membranes are also used in a wide range of biomedical applications that require separations. Considering the fact that most organs (apart from the heart and brain) have separation processes associated with the physiological function (kidneys, lungs, intestines, stomach, etc.), technological solutions have been developed to replace the function of these organs with the help of polymer membranes. This review presents the main biomedical applications of polymer membranes, such as hemodialysis (for chronic kidney disease), membrane-based artificial oxygenators (for artificial lung), artificial liver, artificial pancreas, and membranes for osseointegration and drug delivery systems based on membranes.

Conducting Polymer-Infused Electrospun Fibre Mat Modified by POEGMA Brushes as Antifouling Biointerface

Biofouling on surfaces, caused by the assimilation of proteins, peptides, lipids and microorganisms, leads to contamination, deterioration and failure of biomedical devices and causes implants rejection. To address these issues, various antifouling strategies have been extensively studied, including polyethylene glycol-based polymer brushes. Conducting polymers-based biointerfaces have emerged as advanced surfaces for interfacing biological tissues and organs with electronics. Antifouling of such biointerfaces is a challenge. In this study, we fabricated electrospun fibre mats from sulphonated polystyrene-block-poly(ethylene-ran-butylene)-block-polystyrene (sSEBS), infused with conducting polymer poly(3,4-ethylenedioxythiophene) (PEDOT) (sSEBS-PEDOT), to produce a conductive (2.06 ± 0.1 S/cm), highly porous, fibre mat that can be used as a biointerface in bioelectronic applications. To afford antifouling, here the poly(oligo (ethylene glycol) methyl ether methacrylate) (POEGMA) brushes were grafted onto the sSEBS-PEDOT conducting fibre mats via surface-initiated atom transfer radical polymerization technique (SI-ATRP). For that, a copolymer of EDOT and an EDOT derivative with SI-ATRP initiating sites, 3,4-ethylenedioxythiophene) methyl 2-bromopropanoate (EDOTBr), was firstly electropolymerized on the sSEBS-PEDOT fibre mat to provide sSEBS-PEDOT/P(EDOT-co-EDOTBr). The POEGMA brushes were grafted from the sSEBS-PEDOT/P(EDOT-co-EDOTBr) and the polymerization kinetics confirmed the successful growth of the brushes. Fibre mats with 10-mers and 30-mers POEGMA brushes were studied for antifouling using a BCA protein assay. The mats with 30-mers grafted brushes exhibited excellent antifouling efficiency, ~82% of proteins repelled, compared to the pristine sSEBS-PEDOT fibre mat. The grafted fibre mats exhibited cell viability >80%, comparable to the standard cell culture plate controls. Such conducting, porous biointerfaces with POEGMA grafted brushes are suitable for applications in various biomedical devices, including biosensors, liquid biopsy, wound healing substrates and drug delivery systems.

Active and passive drug release by self-assembled lubricin (PRG4) anti-fouling coatings

Electroactive polymers (EAPs) have been investigated as materials for use in a range of biomedical applications, ranging from cell culture, electrical stimulation of cultured cells as well as controlled delivery of growth factors and drugs. Despite their excellent drug delivery ability, EAPs are susceptible to biofouling thus they often require surface functionalisation with antifouling coatings to limit unwanted non-specific protein adsorption. Here we demonstrate the surface modification of para toluene sulfonate (pTS) doped polypyrrole with the glycoprotein lubricin (LUB) to produce a self-assembled coating that both prevents surface biofouling while also serving as a high-capacity reservoir for cationic drugs which can then be released passively via diffusion or actively via an applied electrical potential. We carried out our investigation in two parts where we initially assessed the antifouling and cationic drug delivery ability of LUB tethered on a gold surface using quartz crystal microbalance with dissipation monitoring (QCM) to monitor molecular interactions occurring on a gold sensor surface. After confirming the ability of tethered LUB nano brush layers on a gold surface, we introduced an electrochemically grown EAP layer to act as the immobilisation surface for LUB before subsequently introducing the cationic drug doxorubicin hydrochloride (DOX). The release of cationic drug was then investigated under passive and electrochemically stimulated conditions. High-performance liquid chromatography (HPLC) was then carried out to quantify the amount of DOX released. It was shown that the amount of DOX released from nano brush layers of LUB tethered on gold and EAP surfaces could be increased by up to 30% per minute by applying a positive electrochemically stimulating pulse at 0.8 V for one minute. Using bovine serum albumin (BSA), we show that DOX loaded LUB tethered on para toluene sulfonic acid (pTS) doped polypyrrole retained antifouling ability of up to 75% when compared to unloaded tethered LUB. This work demonstrates the unique, novel ability of tethered LUB to actively participate in the delivery of cationic therapeutics on different substrate surfaces. This study could lead to the development of versatile multifunctional biomaterials for use in wide range of biomedical applications, such as dual drug delivery and lubricating coatings, dual drug delivery and antifouling coatings, cellular recording and stimulation.

Recent Advances in Stimuli-Responsive Doxorubicin Delivery Systems for Liver Cancer Therapy

Doxorubicin (DOX) is one of the most commonly used drugs in liver cancer. Unfortunately, the traditional chemotherapy with DOX presents many limitations, such as a systematic release of DOX, affecting both tumor tissue and healthy tissue, leading to the apparition of many side effects, multidrug resistance (MDR), and poor water solubility. Furthermore, drug delivery systems' responsiveness has been intensively studied according to the influence of different internal and external stimuli on the efficiency of therapeutic drugs. In this review, we discuss both internal stimuli-responsive drug-delivery systems, such as redox, pH and temperature variation, and external stimuli-responsive drug-delivery systems, such as the application of magnetic, photo-thermal, and electrical stimuli, for the controlled release of Doxorubicin in liver cancer therapy, along with the future perspectives of these smart delivery systems in liver cancer therapy.

Biodegradable bioelectronics for biomedical applications

Biodegradable polymers have been widely used in tissue engineering with the potential to be replaced by regenerative tissue. While conventional bionic interfaces are designed to be implanted in living tissue and organs permanently, biocompatible and biodegradable electronic materials are now progressing a paradigm shift towards transient and regenerative bionic engineering. For example, biodegradable bioelectronics can monitor physiologies in a body, transiently rehabilitate disease symptoms, and seamlessly form regenerative interfaces from synthetic electronic devices to tissues by reducing inflammatory foreign-body responses. Conventional electronic materials have not readily been considered biodegradable. However, several strategies have been adopted for designing electroactive and biodegradable materials systems: (1) conductive materials blended with biodegradable components, (2) molecularly engineered conjugated polymers with biodegradable moieties, (3) naturally derived conjugated biopolymers, and (4) aqueously dissolvable metals with encapsulating layers. In this review, we endeavor to present the technical bridges from electrically active and biodegradable material systems to edible and biodegradable electronics as well as transient bioelectronics with pre-clinical bio-instrumental applications, including biodegradable sensors, neural and tissue engineering, and intelligent drug delivery systems.

Current Advances in Nano-Based and Polymeric Stimuli-Responsive Drug Delivery Targeting the Ocular Microenvironment: A Review and Envisaged Future Perspectives

Optimal vision remains one of the most essential elements of the sensory system continuously threatened by many ocular pathologies. Various pharmacological agents possess the potential to effectively treat these ophthalmic conditions; however, the use and efficacy of conventional ophthalmic formulations is hindered by ocular anatomical barriers. Recent novel designs of ophthalmic drug delivery systems (DDS) using nanotechnology show promising prospects, and ophthalmic formulations based on nanotechnology are currently being investigated due to their potential to bypass these barriers to ensure successful ocular drug delivery. More recently, stimuli-responsive nano drug carriers have gained more attention based on their great potential to effectively treat and alleviate many ocular diseases. The attraction is based on their biocompatibility and biodegradability, unique secondary conformations, varying functionalities, and, especially, the stimuli-enhanced therapeutic efficacy and reduced side effects. This review introduces the design and fabrication of stimuli-responsive nano drug carriers, including those that are responsive to endogenous stimuli, viz., pH, reduction, reactive oxygen species, adenosine triphosphate, and enzymes or exogenous stimuli such as light, magnetic field or temperature, which are biologically related or applicable in clinical settings. Furthermore, the paper discusses the applications and prospects of these stimuli-responsive nano drug carriers that are capable of overcoming the biological barriers of ocular disease alleviation and/or treatment for in vivo administration. There remains a great need to accelerate the development of stimuli-responsive nano drug carriers for clinical transition and applications in the treatment of ocular diseases and possible extrapolation to other topical applications such as ungual or otic drug delivery.

On-demand electrochemically controlled compound release from an ultrasonically powered implant

On-demand drug delivery systems are promising for a wide range of therapeutic applications. When combined with wireless implants for controlled drug delivery, they can reduce overall dosage and side effects. Here, we demonstrate release of fluorescein from a novel on-demand release system for negatively charged compounds. The release system is based on a modified electroresponsive polypyrrole nanoparticulate film designed to minimize ion exchange with the stored compound - a major passive leakage mechanism. We further designed an ultrasonically powered mm-sized implant to electronically control the on-demand drug delivery system in vivo. Release kinetics are characterized both in vitro and in vivo in mice using fluorescein as a model drug, demonstrating the feasibility of wireless, controllable drug release using an ultrasonically powered implant.

Multitasking smart hydrogels based on the combination of alginate and poly(3,4-ethylenedioxythiophene) properties: A review

Poly(3,4-ethylenedioxythiophene) (PEDOT), a very stable and biocompatible conducting polymer, and alginate (Alg), a natural water-soluble polysaccharide mainly found in the cell wall of various species of brown algae, exhibit very different but at the same complementary properties. In the last few years, the remarkable capacity of Alg to form hydrogels and the electro-responsive properties of PEDOT have been combined to form not only layered composites (PEDOT-Alg) but also interpenetrated multi-responsive PEDOT/Alg hydrogels. These materials have been found to display outstanding properties, such as electrical conductivity, piezoelectricity, biocompatibility, self-healing and re-usability properties, pH and thermoelectric responsiveness, among others. Consequently, a wide number of applications are being proposed for PEDOT-Alg composites and, especially, PEDOT/Alg hydrogels, which should be considered as a new kind of hybrid material because of the very different chemical nature of the two polymeric components. This review summarizes the applications of PEDOT-Alg and PEDOT/Alg in tissue interfaces and regeneration, drug delivery, sensors, microfluidics, energy storage and evaporators for desalination. Special attention has been given to the discussion of multi-tasking applications, while the new challenges to be tackled based on aspects not yet considered in either of the two polymers have also been highlighted.

Conductive Microneedle Patch with Electricity-Triggered Drug Release Performance for Atopic Dermatitis Treatment

Atopic dermatitis (AD) is a chronic inflammatory skin disease that seriously affects the life quality of patients. Topical administration of glucocorticoids is considered to be the most effective anti-inflammatory treatment. However, due to the barrier function of skin, only less than 20% of topical drug molecules could diffuse into the skin. Therefore, it is of great importance to develop an effective strategy to improve AD therapy. In this study, we reported a two-electrode microneedle patch (t-EMNP) composed of a polylactic acid-platinum (PLA-Pt) MN array and polylactic acid-platinum-polypyrrole (PLA-Pt-PPy) MN array for improving the transdermal drug delivery efficacy. The drug loading capability of MNs could be altered by employing different polymerization times and drug concentrations. The drug release rate of MNs could be changed by applying different voltages. We further developed a controlled transdermal drug delivery system (c-TDDS) based on this two-electrode microneedle patch (t-EMNP), exhibiting the remarkable performance of the electricity-triggered drug release profile. The drugs could be released with electrical stimulation, while there was almost no drug release without electrical stimulation. For AD treatment in vivo, this MN patch with electricity-triggered drug release performance could effectively deliver more drugs into the skin compared with other controls such as dexamethasone cream, which efficiently alleviate AD. In sum, this work not only developed a smart patch for improving AD treatment but also provided a promising approach of transdermal drug delivery on demand.

Zwitterionic Conducting Polymers: From Molecular Design, Surface Modification, and Interfacial Phenomenon to Biomedical Applications

Conducting polymers (CPs) have gained attention as electrode materials in bioengineering mainly because of their mechanical softness compared to conventional inorganic materials. To achieve better performance and broaden bioelectronics applications, the surface modification of soft zwitterionic polymers with antifouling properties represents a facile approach to preventing unwanted nonspecific protein adsorption and improving biocompatibility. This feature article emphasizes the antifouling properties of zwitterionic CPs, accompanied by their molecular synthesis and surface modification methods and an analysis of the interfacial phenomenon. Herein, commonly used methods for zwitterionic functionalization on CPs are introduced, including the synthesis of zwitterionic moieties on CP molecules and postsurface modification, such as the grafting of zwitterionic polymer brushes. To analyze the chain conformation, the structure of bound water in the vicinity of zwitterionic CPs and biomolecule behavior, such as protein adsorption or cell adhesion, provide critical insights into the antifouling properties. Integrating these characterization techniques offers general guidelines and paves the way for designing new zwitterionic CPs for advanced biomedical applications. Recent advances in newly designed zwitterionic CP-based electrodes have demonstrated outstanding potential in modern biomedical applications.

Intrinsically Stretchable Poly(3,4-ethylenedioxythiophene) Conducting Polymer Film for Flexible Electronics

The aim of this study was to synthesize an intrinsically stretchable conductive polymer (CP) by atom transfer radical polymerization (ATRP). For this purpose, poly(3,4-ethyilenedioxythiophene) (PEDOT) was synthesized as a backbone, while poly(acrylate-urethane) (PAU) was grafted onto the PEDOT backbone to form graft polymers PEDOT-g-PAU. Different concentrations of acrylate-urethane (AU) were used to synthesize PAU side chains of different lengths. The successful synthesis of the obtained intermediates and products (PEDOT-g-PAU) was confirmed by infrared spectroscopy and nuclear magnetic resonance. Thermal properties were evaluated by differential scanning calorimetry and thermogravimetric analysis, while conductivity was determined by four-point probe measurement. A simple tensile test was performed to characterize the ductility of the samples. PEDOT-g-PAU has shown high stretchability of up to 500% and, therefore, could potentially be used in skin-worn flexible electronics, while additional subsequent doping is required to improve the deterioration of electrical properties after the addition of the insulating urethane layer.

Poly(3,4-ethylenedioxythiophene)-Based Neural Interfaces for Recording and Stimulation: Fundamental Aspects and In Vivo Applications

Next-generation neural interfaces for bidirectional communication with the central nervous system aim to achieve the intimate integration with the neural tissue with minimal neuroinflammatory response, high spatio-temporal resolution, very high sensitivity, and readout stability. The design and manufacturing of devices for low power/low noise neural recording and safe and energy-efficient stimulation that are, at the same time, conformable to the brain, with matched mechanical properties and biocompatibility, is a convergence area of research where neuroscientists, materials scientists, and nanotechnologists operate synergically. The biotic-abiotic neural interface, however, remains a formidable challenge that prompts for new materials platforms and innovation in device layouts. Conductive polymers (CP) are attractive materials to be interfaced with the neural tissue and to be used as sensing/stimulating electrodes because of their mixed ionic-electronic conductivity, their low contact impedance, high charge storage capacitance, chemical versatility, and biocompatibility. This manuscript reviews the state-of-the-art of poly(3,4-ethylenedioxythiophene)-based neural interfaces for extracellular recording and stimulation, focusing on those technological approaches that are successfully demonstrated in vivo. The aim is to highlight the most reliable and ready-for-clinical-use solutions, in terms of materials technology and recording performance, other than spot major limitations and identify future trends in this field.

Stimuli-Responsive Microneedles as a Transdermal Drug Delivery System: A Demand-Supply Strategy

Microneedles are one of the most prominent approaches capable of physically disrupting the stratum corneum without devastating the deeper tissues to deliver both small molecules and macromolecules into the viable epidermis/dermis for local/systemic effects. Over the past two decades, microneedles have caught the attention of many researchers because of their outstanding advantages over oral and parenteral drug delivery systems such as self-administration, pain-free, steady-plasma concentration maintenance, avoidance of first-pass hepatic biotransformation, and so on. So far, scientists have reported various types of microneedle patches to deliver the loaded therapeutics as soon as the microneedles are inserted into the skin, regardless of the demand for therapeutics to treat a specific condition. This way of drug delivery can lead to potential risks such as poor therapeutic efficacy or drug overdose. The stimuli-responsive microneedles are the most predominant tool to achieve the on-demand/need-based drug delivery, leading to safe and effective treatment. Various natural and synthetic polymers that can undergo significant transitions such as swelling, shrinking, dissolution, or disintegration play a pivotal role in the development of stimuli-responsive microneedles. The current Review provides brief information about the history, emergence, type, and working principles of microneedles. Furthermore, it selectively discusses various exogenous and endogenous stimuli-responsive microneedles along with their mechanism of action involved in treating different disease conditions. Collaterally, the emergence of "closed-loop" combinatorial stimuli-responsive microneedle patches for precise delivery of therapeutics is meticulously canvassed. Subsequently, it covers the patents of different stimuli-responsive microneedles and further highlights the existing challenges and future perspectives concerning clinical application and large-scale production.

Recent advances in the aqueous applications of PEDOT

Water is ubiquitous in life - from making up the majority of the Earth's surface (by area) to over half of the human body (by weight). It stands to reason that materials are likely to contact water at some point during their lifetime. In the specific case of sensors however, there is a need to consider materials that display stable function while immersed in aqueous applications. This mini-review will discuss the most recent advances (2018 to 2021) in the application of the conducting polymer poly(3,4-ethylenedioxythiophene) (PEDOT) in aqueous environments. At its heart, the use of PEDOT in aqueous applications relies on nanoscale understanding and/or nanoengineered structures and properties. This enables their use in water-based settings such as within the human body or buried in agricultural soils.

(Rose Bengal)/(Eosin Yellow)-Gold-Polypyrrole Hybrids: A Design for Dual Photo-Active Nano-System with Ultra-High Loading Capacity

Purpose

Enhancement of the photodynamic/photothermal efficiency of two water-soluble dyes, rose bengal (RB) and eosin yellow (EY), via conjugation to a polymeric nano-system gold-polypyrrole nanoparticle (AuPpy NPs).

Methodology

A multi-step synthesis method and an in situ one-pot synthesis method were used. Loading percentage, particle size, zeta potential, morphology, UV-Vis-NIR spectrophotometry and in vitro photothermal activity were measured. Then, both hybrid nanocomposites were examined for their cytotoxicity and photocytotoxicity on HepG2 cell line as a model for cancer cells.

Results

Dyes loaded in the traditional multi-step method did not exceed 9% w/w, while in the one-pot synthesis method they reached ~67% w/w and ~75% w/w for EY-AuPpy NPs and RB-AuPpy NPs, respectively. UV-Vis-NIR spectrophotometry showed that both nano-systems exhibited intense absorption in the NIR region. The mean size of the nanoparticles was ~31.5 nm (RB-AuPpy NPs) and ~33.6 nm (EY-AuPpy NPs) with zeta potential values of −26.5 mV and −33 mV, respectively. TEM imaging revealed the morphology of both hybrids, showing ultra-nano spherical-shaped gold cores in the case of RB-AuPpy NPs, and different shapes of larger gold cores in the case of EY-AuPpy NPs, both embedded in the polymer film. Conjugation to AuPpy was found to significantly reduce the dark cytotoxicity of both RB and EY, preserving the photocytotoxicity of EY and enhancing the photocytotoxicity of RB.

Conclusion

Gold-polypyrrole nanoparticles represent an effective delivery system to improve the photodynamic and photothermal properties of RB and EY. The in situ one-pot synthesis method provided a means to greatly increase the loading capacity of AuPpy NPs. While both hybrid nanocomposites exhibited greatly diminished dark cytotoxicity, RB-AuPpy NPs showed significantly enhanced photocytotoxicity compared to the free dyes. This pattern enables the safe use of both dyes in high concentrations with sustained action, reducing dose frequency and side effects.

Multifunctional Biomedical Materials Derived from Biological Membranes

The delicate structure and fantastic functions of biological membranes are the successful evolutionary results of a long-term natural selection process. Their excellent biocompatibility and biofunctionality are widely utilized to construct multifunctional biomedical materials mainly by directly camouflaging materials with single or mixed biological membranes, decorating or incorporating materials with membrane-derived vesicles (e.g., exosomes), and designing multifunctional materials with the structure/functions of biological membranes. Here, the structure-function relationship of some important biological membranes and biomimetic membranes are discussed, such as various cell membranes, extracellular vesicles, and membranes from bacteria and organelles. Selected literature examples of multifunctional biomaterials derived from biological membranes for biomedical applications, such as drug- and gene-delivery systems, tissue-repair scaffolds, bioimaging, biosensors, and biological detection, are also highlighted. These designed materials show excellent properties, such as long circulation time, disease-targeted therapy, excellent biocompatibility, and selective recognition. Finally, perspectives and challenges associated with the clinical applications of biological-membrane-derived materials are discussed.

Advanced Control of Drug Delivery for In Vivo Health Applications via Highly Biocompatible Self-Assembled Organic Nanoparticles

The use of nanostructured materials for targeted and controlled delivery of bioactive molecules is an attractive alternative to conventional drug administration protocols, enabling selective targeting of diseased cells, lower administered dosages, and reduced systemic side effects. Although a variety of nanocarriers have been investigated in recent years, electroactive organic polymer nanoparticles present several exciting advantages. Here we demonstrate that thin films created from nanoparticles synthesized from violanthrone-79, an n-type semiconducting organic material, can incorporate and release dexamethasone in vitro in a highly controlled manner. By systematically altering the nanoparticle formation chemistry, we successfully tailored the size of the nanoparticles between 30 and 145 nm to control the initial amount of drug loaded into the organic particles. The biocompatibility of the different particles was tested using live/dead assays of dorsal root ganglion neurons isolated and cultured from mice, revealing that elevated levels of the sodium dodecyl sulfate surfactant used to create the smaller nanoparticles are cytotoxic; however, cell survival rates in nanoparticles larger than 45 nm exceed 86% and promote neurite growth and elongation. By manipulating the electrical stimulus applied to the electroactive nanoparticle films, we show an accelerated rate of drug release in comparison to passive release in aqueous media. Furthermore, pulsing the electrical stimulus was successfully used to selectively switch the accelerated release rate on and off. By combining the tuning of drug loading (through tailored nanoparticle synthesis) and drug release rate (through electrical stimulus protocols), we demonstrate a highly advanced control of drug delivery dosage in a biocompatible delivery vehicle. This work highlights the significant potential of electroactive organic nanoparticles for implantable devices that can deliver corticosteroids directly to the nervous system for the treatment of inflammation associated with neurological disorders, presenting a translatable pathway toward precision nanomedicine approaches for other drugs and diseases.

Three-Dimensional Printable Conductive Semi-Interpenetrating Polymer Network Hydrogel for Neural Tissue Applications

Intrinsically conducting polymers (ICPs) are widely used to fabricate biomaterials; their application in neural tissue engineering, however, is severely limited because of their hydrophobicity and insufficient mechanical properties. For these reasons, soft conductive polymer hydrogels (CPHs) are recently developed, resulting in a water-based system with tissue-like mechanical, biological, and electrical properties. The strategy of incorporating ICPs as a conductive component into CPHs is recently explored by synthesizing the hydrogel around ICP chains, thus forming a semi-interpenetrating polymer network (semi-IPN). In this work, a novel conductive semi-IPN hydrogel is designed and synthesized. The hybrid hydrogel is based on a poly(N-isopropylacrylamide-co-N-isopropylmethacrylamide) hydrogel where polythiophene is introduced as an ICP to provide the system with good electrical properties. The fabrication of the hybrid hydrogel in an aqueous medium is made possible by modifying and synthesizing the monomers of polythiophene to ensure water solubility. The morphological, chemical, thermal, electrical, electrochemical, and mechanical properties of semi-IPNs were fully investigated. Additionally, the biological response of neural progenitor cells and mesenchymal stem cells in contact with the conductive semi-IPN was evaluated in terms of neural differentiation and proliferation. Lastly, the potential of the hydrogel solution as a 3D printing ink was evaluated through the 3D laser printing method. The presented results revealed that the proposed 3D printable conductive semi-IPN system is a good candidate as a scaffold for neural tissue applications.

Electroactive macromolecular motors as model materials of ectotherm muscles

The electrochemical reaction in liquid electrolytes of conducting polymers, carbon nanotubes, graphenes, among other materials, replicates the active components (macromolecular electro-chemical motors, ions and solvent) and volume variation of the sarcomere in any natural muscles during actuation, allowing the development of electro-chemo-mechanical artificial muscles. Materials, reactions and artificial muscles have been used as model materials, model reactions and model devices of the muscles from ectotherm animals. We present in this perspective the experimental results and a quantitative description of the thermal influence on the reaction extension and energetic achievements of those muscular models using different experimental methodologies. By raising the temperature for 40 °C keeping the extension of the muscular movement the cooperative actuation of the macromolecular motors harvest, saving chemical energy, up to 60% of the reaction energy from the thermal environment. The synergic thermal influence on either, the reaction rate (Arrhenius), the conformational movement rates of the motors (ESCR model) and the diffusion coefficients of ions across polymer matrix (WLF equation) can support the physical chemical foundations for the selection by nature of ectotherm muscles. Macromolecular motors act, simultaneously, as electro-chemo-mechanical and thermo-mechanical transducers. Technological and biological perspectives are presented.