Type I Collagen-Derived Injectable Conductive Hydrogel Scaffolds as Glucose Sensors

Injectable Hydrogels: A Paradigm Tailored with Design, Characterization, and Multifaceted Approaches

Biomaterials denoting self-healing and versatile structural integrity are highly curious in the biomedicine segment. The injectable and/or printable 3D printing technology is explored in a few decades back, which can alter their dimensions temporarily under shear stress, showing potential healing/recovery tendency with patient-specific intervention toward the development of personalized medicine. Thus, self-healing injectable hydrogels (IHs) are stunning toward developing a paradigm for tissue regeneration. This review comprises the designing of IHs, rheological characterization and stability, several benchmark consequences for self-healing IHs, their translation into tissue regeneration of specific types, applications of IHs in biomedical such as anticancer and immunomodulation, wound healing and tissue/bone regeneration, antimicrobial potentials, drugs, gene and vaccine delivery, ocular delivery, 3D printing, cosmeceuticals, and photothermal therapy as well as in other allied avenues like agriculture, aerospace, electronic/electrical industries, coating approaches, patents associated with therapeutic/nontherapeutic avenues, and numerous futuristic challenges and solutions.

Resorbable conductive materials for optimally interfacing medical devices with the living

Implantable and wearable bioelectronic systems are arising growing interest in the medical field. Linking the microelectronic (electronic conductivity) and biological (ionic conductivity) worlds, the biocompatible conductive materials at the electrode/tissue interface are key components in these systems. We herein focus more particularly on resorbable bioelectronic systems, which can safely degrade in the biological environment once they have completed their purpose, namely, stimulating or sensing biological activity in the tissues. Resorbable conductive materials are also explored in the fields of tissue engineering and 3D cell culture. After a short description of polymer-based substrates and scaffolds, and resorbable electrical conductors, we review how they can be combined to design resorbable conductive materials. Although these materials are still emerging, various medical and biomedical applications are already taking shape that can profoundly modify post-operative and wound healing follow-up. Future challenges and perspectives in the field are proposed.

Recent Advances and Developments in Injectable Conductive Polymer Gels for Bioelectronics

Soft matter bioelectronics represents an emerging and interdisciplinary research frontier aiming to harness the synergy between biology and electronics for advanced diagnostic and healthcare applications. In this context, a whole family of soft gels have been recently developed with self-healing ability and tunable biological mimetic features to act as a tissue-like space bridging the interface between the electronic device and dynamic biological fluids and body tissues. This review article provides a comprehensive overview of electroactive polymer gels, formed by noncovalent intermolecular interactions and dynamic covalent bonds, as injectable electroactive gels, covering their synthesis, characterization, and applications. First, hydrogels crafted from conducting polymers (poly(3,4-ethylene-dioxythiophene) (PEDOT), polyaniline (PANi), and polypyrrole (PPy))-based networks which are connected through physical interactions (e.g., hydrogen bonding, π-π stacking, hydrophobic interactions) or dynamic covalent bonds (e.g., imine bonds, Schiff-base, borate ester bonds) are addressed. Injectable hydrogels involving hybrid networks of polymers with conductive nanomaterials (i.e., graphene oxide, carbon nanotubes, metallic nanoparticles, etc.) are also discussed. Besides, it also delves into recent advancements in injectable ionic liquid-integrated gels (iongels) and deep eutectic solvent-integrated gels (eutectogels), which present promising avenues for future research. Finally, the current applications and future prospects of injectable electroactive polymer gels in cutting-edge bioelectronic applications ranging from tissue engineering to biosensing are outlined.

Towards the design of mechanical flexible electrodes for sensing: Self-standing polypyrrole-copper nanocomposites

Self-standing electrodes with intrinsic conductivity and high electrocatalytic activity emerge as an alternative to existing sensors given their promising flexibility and wearability. Herein we demonstrate the fabrication of flexible sensors based on a hybrid nanocomposite of self-supported polypyrrole electrodes modified with copper nanoparticles (PPy-Cu) for the electrochemical detection of dopamine. The surface morphology and composition of flexible nanocomposite electrodes was studied using scanning electron microscopy (SEM), in combination with elemental mapping through energy dispersive X-ray spectroscopy (EDS). Surface characterization by X-ray photoelectron spectroscopy (XPS) revealed that copper exists in both Cu(0) and Cu(II) forms. The incorporation of copper nanoparticles in the self-standing polypyrrole matrix introduced additional electroactive sites, further enhancing charge transfer, and improving the device's sensitivity. The sensing capability of self-standing PPy-Cu electrodes was evaluated using chronoamperometric measurements and optimized at various copper electrodeposition times. PPy-Cu 120s showed great performance for dopamine sensing with a low limit of detection of 1.19 μM and a linear range of 2.5 μM-250 μM. Additionally, the self-standing sensor is comprised entirely of Polypyrrole, a biocompatible polymer, and Copper nanoparticles, making it sustainable and environmentally friendly. These encouraging results pave the way for the development of next-generation flexible sensors for the detection of neurotransmitters and environmentally relevant analytes.

Current advancements and prospects of enzymatic and non-enzymatic electrochemical glucose sensors

This review discusses the most current developments and future perspectives in enzymatic and non-enzymatic glucose sensors, which have notably evolved over the preceding quadrennial period. Furthermore, a thorough exploration encompassed the sensor's intricate fabrication processes, the diverse range of materials employed, the underlying principles of detection, and an in-depth assessment of the sensors' efficacy in detecting glucose levels within essential bodily fluids such as human blood serums, urine, saliva, and interstitial fluids. It is worth noting that the accurate quantification of glucose concentrations within human blood has been effectively achieved by utilizing classical enzymatic sensors harmoniously integrated with optical and electrochemical transduction mechanisms. Monitoring glucose levels in various mediums has attracted exceptional attention from industrial to academic researchers for diabetes management, food quality control, clinical medicine, and bioprocess inspection. There has been an enormous demand for the creation of novel glucose sensors over the past ten years. Research has primarily concentrated on succeeding biocompatible and enhanced sensing abilities related to the present technologies, offering innovative avenues for more effective glucose sensors. Recent developments in wearable optical and electrochemical sensors with low cost, high stability, point-of-care testing, and online tracking of glucose concentration levels in biological fluids can aid in managing and controlling diabetes globally. New nanomaterials and biomolecules that can be used in electrochemical sensor systems to identify glucose concentration levels are developed thanks to advances in nanoscience and nanotechnology. Both enzymatic and non-enzymatic glucose electrochemical sensors have garnered much interest recently and have made significant strides in detecting glucose levels. In this review, we summarise several categories of non-enzymatic glucose sensor materials, including composites, non-precious transition metals and their metal oxides, hydroxides, precious metals and their alloys, carbon-based materials, conducting polymers, metal-organic framework (MOF)-based electrocatalysts, and wearable device-based glucose sensors deeply.

The Evolving Role of Proteins in Wearable Sweat Biosensors

Sweat is an increasingly popular biological medium for fitness monitoring and clinical diagnostics. It contains an abundance of biological information and is available continuously and noninvasively. Sweat-sensing devices often employ proteins in various capacities to create skin-friendly matrices that accurately extract valuable and time-sensitive information from sweat. Proteins were first used in sensors as biorecognition elements in the form of enzymes and antibodies, which are now being tuned to operate at ranges relevant for sweat. In addition, a range of structural proteins, sometimes assembled in conjunction with polymers, can provide flexible and compatible matrices for skin sensors. Other proteins also naturally possess a range of functionalities─as adhesives, charge conductors, fluorescence emitters, and power generators─that can make them useful components in wearable devices. Here, we examine the four main components of wearable sweat sensors─the biorecognition element, the transducer, the scaffold, and the adhesive─and the roles that proteins have played so far, or promise to play in the future, in each component. On a case-by-case basis, we analyze the performance characteristics of existing protein-based devices, their applicable ranges of detection, their transduction mechanism and their mechanical properties. Thereby, we review and compare proteins that can readily be used in sweat sensors and others that will require further efforts to overcome design, stability or scalability challenges. Incorporating proteins in one or multiple components of sweat sensors could lead to the development and deployment of tunable, greener, and safer biosourced devices.

Recent Progress in Biomedical Sensors Based on Conducting Polymer Hydrogels

Biosensors are increasingly taking a more active role in health science. The current needs for the constant monitoring of biomedical signals, as well as the growing spending on public health, make it necessary to search for materials with a combination of properties such as biocompatibility, electroactivity, resorption, and high selectivity to certain bioanalytes. Conducting polymer hydrogels seem to be a very promising materials, since they present many of the necessary properties to be used as biosensors. Furthermore, their properties can be shaped and enhanced by designing conductive polymer hydrogel-based composites with more specific functionalities depending on the end application. This work will review the recent state of the art of different biological hydrogels for biosensor applications, discuss the properties of the different components alone and in combination, and reveal their high potential as candidate materials in the fabrication of all-organic diagnostic, wearable, and implantable sensor devices.

Preparation, Characterization and ex vivo Skin Permeability Evaluation of Type I Collagen-Loaded Liposomes

Purpose

In the present study, we prepared collagen liposomes with the addition of polyol, which is expected to not only increase the solubility of collagen but also improve skin penetration.

Methods

Collagen liposomes were prepared by the film dispersion method, and their characteristics, integrity and biosafety were evaluated by Fourier transform infrared spectroscopy (FTIR), UV-VIS spectroscopy, polyacrylamide gel electrophoresis (SDS-PAGE), dynamic light scattering (DLS) and transmission electron microscope (TEM). The transdermal absorption of collagen and collagen liposomes were tested by an ex vivo horizontal Valia-Chien diffusion cell system.

Results

We first demonstrated that collagen extracted from bovine Achilles tendon was type I collagen. The results of DLS measurement and TEM observation showed that the collagen liposomes were spherical in shape with average diameter (75.34±0.93 nm) and maintained high stability at low temperature (4°C) for at least 42 days without toxicity. The encapsulation rate of collagen liposomes was 57.80 ± 0.51%, and SDS-PAGE analysis showed that collagen was intact in liposomes. Finally, permeability studies indicated that the collagen-loaded liposomes more easily penetrated the skin compared to collagen itself.

Conclusion

This study proposed a new method to improve the bioavailability and permeability of bovine type I collagen, which improves the applicability of collagen in biomedicine, cosmeceuticals and pharmaceutical industries.

Recent Development of Self-Powered Tactile Sensors Based on Ionic Hydrogels

Hydrogels are three-dimensional polymer networks with excellent flexibility. In recent years, ionic hydrogels have attracted extensive attention in the development of tactile sensors owing to their unique properties, such as ionic conductivity and mechanical properties. These features enable ionic hydrogel-based tactile sensors with exceptional performance in detecting human body movement and identifying external stimuli. Currently, there is a pressing demand for the development of self-powered tactile sensors that integrate ionic conductors and portable power sources into a single device for practical applications. In this paper, we introduce the basic properties of ionic hydrogels and highlight their application in self-powered sensors working in triboelectric, piezoionic, ionic diode, battery, and thermoelectric modes. We also summarize the current difficulty and prospect the future development of ionic hydrogel self-powered sensors.

Advances in the Translation of Electrochemical Hydrogel-Based Sensors

Novel biomaterials for bio- and chemical sensing applications have gained considerable traction in the diagnostic community with rising trends of using biocompatible and lowly cytotoxic material. Hydrogel-based electrochemical sensors have become a promising candidate for their swellable, nano-/microporous, and aqueous 3D structures capable of immobilizing catalytic enzymes, electroactive species, whole cells, and complex tissue models, while maintaining tunable mechanical properties in wearable and implantable applications. With advances in highly controllable fabrication and processability of these novel biomaterials, the possibility of bio-nanocomposite hydrogel-based electrochemical sensing presents a paradigm shift in the development of biocompatible, "smart," and sensitive health monitoring point-of-care devices. Here, recent advances in electrochemical hydrogels for the detection of biomarkers in vitro, in situ, and in vivo are briefly reviewed to demonstrate their applicability in ideal conditions, in complex cellular environments, and in live animal models, respectively, to provide a comprehensive assessment of whether these biomaterials are ready for point-of-care translation and biointegration. Sensors based on conductive and nonconductive polymers are presented, with highlights of nano-/microstructured electrodes that provide enhanced sensitivity and selectivity in biocompatible matrices. An outlook on current challenges that shall be addressed for the realization of truly continuous real-time sensing platforms is also presented.

Hemoglobin I from Lucina pectinata on Collagen Scaffold: A Prospective Hydrogen Sulfide Scavenger

Hydrogen sulfide (H2S), independently of being a toxic gas with a characteristic smell of rotten eggs, is a crucial signaling molecule with significant physiological functions. Given the rapid diffusivity of the gas, it is a challenge to develop robust sensors and biomarkers to quantify free or bound H2S. In addition, there is the need to further develop a robust biosystem to efficiently trap or scavenge H2S from different producing environments. The work presented here uses recombinant met-aquo rHbI (rHbI-H2O) immobilization techniques on collagen to determine its ability to bind H2S due to its high affinity ( $1.24\times {10}^8$  M-1). The hemeprotein will function as a scavenger on this scaffold system. UV-Vis absorption and UV-Vis diffuse reflectance (%R) spectroscopy of rHbI-H2O and rHbI-sulfide (rHbI-H2S) complex in solution and collagen scaffold demonstrated that the heme chromophore retains its reactivity and properties. UV-Vis diffuse reflectance measurements, transformed using the Kubelka-Munk function (K-M function), show a linear correlation ( $R_2=0.9987$ and 0.9916) of rHbI-H2O and rHbI-H2S within concentrations from 1 μM to 35 μM for derivatives. The extraordinary affinity of rHbI-H2O for H2S suggests recombinant met-aquo HbI in a collagen scaffold is an excellent scavenger moiety for hydrogen sulfide. These findings give insight into H2S trapping using the rHbI-H2O-collagen scaffold, where the rHbI-H2S concentration can be determined. Future pathways are to work toward the development of a met-aquo rHbI collagen solution capable of being printed as single drops on polymer, cotton or chromatographic paper. Upon exposure of these matrixes to H2S, the rHbI-H2S complex is formed and its concentration determined using UV-Vis diffuse reflectance technique.

Shaping Macromolecules for Sensing Applications—From Polymer Hydrogels to Foldamers

Sensors are tools for detecting, recognizing, and recording signals from the surrounding environment. They provide measurable information on chemical or physical changes, and thus are widely used in diagnosis, environment monitoring, food quality checks, or process control. Polymers are versatile materials that find a broad range of applications in sensory devices for the biomedical sector and beyond. Sensory materials are expected to exhibit a measurable change of properties in the presence of an analyte or a stimulus, characterized by high sensitivity and selectivity of the signal. Signal parameters can be tuned by material features connected with the restriction of macromolecule shape by crosslinking or folding. Gels are crosslinked, three-dimensional networks that can form cavities of different sizes and forms, which can be adapted to trap particular analytes. A higher level of structural control can be achieved by foldamers, which are macromolecules that can attain well-defined conformation in solution. By increasing control over the three-dimensional structure, we can improve the selectivity of polymer materials, which is one of the crucial requirements for sensors. Here, we discuss various examples of polymer gels and foldamer-based sensor systems. We have classified and described applied polymer materials and used sensing techniques. Finally, we deliberated the necessity and potential of further exploration of the field towards the increased selectivity of sensory devices.

Conductive Hydrogel-Based Electrochemical Sensor: A Soft Platform for Capturing Analyte

Electrode modifications for electrochemical sensors attract a lot of attention every year. Among them, hydrogels are a relatively special class of electrode modifier. Since hydrogels often contain polymers, even though they are conductive polymers, they are not ideal electrode modifiers because of their poor conductivity. However, the micro-aqueous environment and the three-dimensional structure of hydrogels are an excellent platform for immobilizing bioactive molecules and maintaining their activity. This gives the hydrogel-modified electrochemical sensor the potential to perform specific recognition. At the same time, the rapid development of nanomaterials also makes the composite hydrogel have good electrical conductivity. This has led many scientists to become interested in hydrogel-based electrochemical sensors. In this review, we summarize the development process of hydrogel-based electrochemical sensors, starting from 2000. Hydrogel-based electrochemical sensors were initially used only as a carrier for biomolecules, mostly for loading enzymes and for specific recognition. With the widespread use of noble metal nanoparticles and carbon materials, hydrogels can now be used to prepare enzyme-free sensors. Although there are some sporadic studies on the use of hydrogels for practical applications, the vast majority of reports are still limited to the detection of common model molecules, such as glucose and H2O2. In the review, we classify hydrogels according to their different conducting strategies, and present the current status of the application of different hydrogels in electrochemical sensors. We also summarize the advantages and shortcomings of hydrogel-based electrochemical sensors. In addition, future prospects regarding hydrogel for electrochemical sensor use have been provided at the end.

Applications of scaffold-based advanced materials in biomedical sensing

There have been many efforts to synthesize advanced materials that are capable of real-time specific recognition of a molecular target, and allow the quantification of a variety of biomolecules. Scaffold materials have a porous structure, with a high surface area and their intrinsic nanocavities can accommodate cells and macromolecules. The three-dimensional structure (3D) of scaffolds serves not only as a fibrous structure for cell adhesion and growth in tissue engineering, but can also provide the controlled release of drugs and other molecules for biomedical applications. There has been a limited number of reports on the use of scaffold materials in biomedical sensing applications. This review highlights the potential of scaffold materials in the improvement of sensing platforms and summarizes the progress in the application of novel scaffold-based materials as sensor, and discusses their advantages and limitations. Furthermore, the influence of the scaffold materials on the monitoring of infectious diseases such as severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and bacterial infections, was reviewed.

Regulation of Blood Glucose Using Islets Encapsulated in a Melanin-Modified Immune-Shielding Hydrogel

Islet transplantation is currently a promising treatment for type 1 diabetes mellitus. However, the foreign body reaction and retrieval difficulty often lead to transplantation failure and hinder the clinical application. To address these two challenges, we propose a balanced charged sodium alginate-polyethyleneimine-melanin (SA-PEI-Melanin) threadlike hydrogel with immune shielding and retrievable properties. The attractiveness of this study lies in that the introduction of melanin can stimulate insulin secretion, especially under near-infrared (NIR) irradiation. After demonstrating a good immune-shielding effect, we performed an in vivo transplantation experiment. The results showed that the blood glucose level in the SA-PEI-Melanin group was stably controlled below the diabetic blood glucose criterion, and this blood glucose level could be further adjusted after NIR irradiation. In addition, the evaluation after retrieving the SA-PEI-Melanin hydrogel indicated that the islets still maintained a normal physiological function, further proving its excellent immunological protection. This study provides a new approach for the accurate regulation of blood glucose in patients with type 1 diabetes mellitus and contributes to developing a promising transplant system to reconcile real-time and precise light-defined insulin secretion regulation.

Click chemistry-based biopolymeric hydrogels for regenerative medicine

Click chemistry is not a single specific reaction, but describes ways of generating products which emulate examples in nature. Click reactions occur in one pot, are not disturbed by water, generate minimal and inoffensive byproducts, and are characterized by a high thermodynamic driving force, driving the reaction quickly and irreversibly towards a high yield of a single reaction product. As a result, over the past 15 years it has become a very useful bio-orthogonal method for the preparation of chemical cross-linked biopolymer-based hydrogel, in the presence of e.g. growth factors and live cells, or in-vivo. Biopolymers are renewable and non-toxic, providing a myriad of potential backbone toolboxes for hydrogel design. The goal of this review is to summarize recent advances in the development of click chemistry-based biopolymeric hydrogels, and their applications in regenerative medicine. In particular, various click chemistry approaches, including copper-catalyzed azide-alkyne cycloaddition reactions, copper-free click reactions (e.g. the Diels-Alder reactions, the strain-promoted azide-alkyne cycloaddition reactions, the radical mediated thiol-ene reactions, and the oxime-forming reactions), and pseudo-click reactions (e.g. the thiol-Michael addition reactions and the Schiff base reactions) are highlighted in the first section. In addition, numerous biopolymers, including proteins (e.g. collagen, gelatin, silk, and mucin), polysaccharides (e.g. hyaluronic acid, alginate, dextran, and chitosan) and polynucleotides (e.g. deoxyribonucleic acid), are discussed. Finally, we discuss biopolymeric hydrogels, cross-linked by click chemistry, intended for the regeneration of skin, bone, spinal cord, cartilage, and cornea. This article provides new insights for readers in terms of the design of regenerative medicine, and the use of biopolymeric hydrogels based on click chemistry reactions.

Conductive Skeleton-Heterostructure Composites Based on Chrome Shavings for Enhanced Electromagnetic Interference Shielding

Renewable bio-based electromagnetic interference (EMI) shielding materials receive increasing attention undoubtedly. However, there is still a challenge to use raw biomass materials to construct a significant structure through an effortless and environmental route for EMI shielding applications. Herein, for the first time, we demonstrated a hybrid composite of multi-walled carbon nanotube/polypyrrole/chrome-tanned collagen fiber (MWCNT/PPy/CF), which utilized waste chrome shavings as a matrix. X-ray photoelectron spectroscopy reveals that the chromium on the CF has a binding effect on the PPy layer, which endows the tight integration between the CF and PPy layer. After the MWCNT network was loaded on the PPy layer, this ternary structure could provide stable conductive paths and a rich number of polarized interfaces. The MWCNT/PPy/CF composite exhibits superior electrical conductivity (354 ± 52 S/m), higher than PPy/CF (222 ± 38 S/m) and MWCNT/CF (104 ± 11 S/m), owing to the synergy of dual conductive structures. Notably, the shielding effectiveness (SE) value of the MWCNT/PPy/CF composite reaches 30 dB in the X band at a thickness of 0.48 mm. The shielding effectiveness of reflection (SE_R) (9.1 dB) is similar to that of PPy/CF (8.2 dB), while the shielding effectiveness of absorption (SE_A) is significantly improved from 15.3 dB (PPy/CF) to 20.4 dB (MWCNT/PPy/CF) due to the additional coverage of the MWCNT network. This indicates the synergy between the MWCNT network and conductive PPy/CF skeleton. This work provided a method to prepare sustainable and low-cost renewable EMI shielding materials using chrome shavings. Meanwhile, this novel structure combining a conductive skeleton and heterostructure can be considered as a potential application in relevant fields.

Design Strategies of Conductive Hydrogel for Biomedical Applications

Conductive hydrogel, with electroconductive properties and high water content in a three-dimensional structure is prepared by incorporating conductive polymers, conductive nanoparticles, or other conductive elements, into hydrogel systems through various strategies. Conductive hydrogel has recently attracted extensive attention in the biomedical field. Using different conductivity strategies, conductive hydrogel can have adjustable physical and biochemical properties that suit different biomedical needs. The conductive hydrogel can serve as a scaffold with high swelling and stimulus responsiveness to support cell growth in vitro and to facilitate wound healing, drug delivery and tissue regeneration in vivo. Conductive hydrogel can also be used to detect biomolecules in the form of biosensors. In this review, we summarize the current design strategies of conductive hydrogel developed for applications in the biomedical field as well as the perspective approach for integration with biofabrication technologies.

Natural-based Hydrogels: A Journey from Simple to Smart Networks for Medical Examination

Natural hydrogels, due to their unique biological properties, have been used extensively for various medical and clinical examinations that are performed to investigate the signs of disease. Recently, complex-crosslinking strategies improved the mechanical properties and advanced approaches have resulted in the introduction of naturally derived hydrogels that exhibit high biocompatibility, with shape memory and self-healing characteristics. Moreover, the creation of self-assembled natural hydrogels under physiological conditions has provided the opportunity to engineer fine-tuning properties. To highlight recent studies of natural-based hydrogels and their applications for medical investigation, a critical review was undertaken using published papers from the Science Direct database. This review presents different natural-based hydrogels (natural, natural-synthetic hybrid and complex-crosslinked hydrogels), their historical evolution, and recent studies of medical examination applications. The application of natural-based hydrogels in the design and fabrication of biosensors, catheters and medical electrodes, detection of cancer, targeted delivery of imaging compounds (bioimaging) and fabrication of fluorescent bioprobes is summarised here. Without doubt, in future, more useful and practical concepts will be derived to identify natural-based hydrogels for a wide range of clinical examination applications.

Self-healing conductive hydrogels: preparation, properties and applications

Conductive hydrogels have generated great interest in biomedical and electrical fields. However, conventional conductive hydrogels usually lack self-healing properties, which might be unfavorable for their application. Conductive self-healing hydrogels with excellent performance for applications in the biomedical and electrical fields are growing in number. In this review paper, the progress related to conductive self-healing hydrogels is summarized. The self-healing mechanism is classified to demonstrate the design and synthesis of conductive self-healing hydrogels and their applications in tissue engineering, wound healing, electronic skin, sensors and self-repaired circuits are presented and discussed. The future development of conductive self-healing hydrogels and problems that need to be solved are also described.

Simple Thermal Pretreatment Strategy to Tune Mechanical and Antifouling Properties of Zwitterionic Hydrogels

Zwitterionic hydrogels are promising biomaterials because of their high water content, three-dimensional network structure, and antifouling property. However, it still remains unclear about how mechanical properties of zwitterionic hydrogels affect their antifouling property. In this work, we propose a simple, thermal-pretreatment method to fabricate poly(sulfobetaine methacrylate) (pSBMA) hydrogels with varied mechanical properties that can be readily tuned by thermal pretreatment time and cross-linker density, as well as to correlate their mechanical property with antifouling property. The resulting thermal-treated pSBMA hydrogels show significantly enhanced mechanical properties with tunable compressive modulus and elastic modulus as compared to the untreated hydrogels. A combination of ELISA investigations and short-term cell adhesion assays also confirm that pSBMA hydrogels exhibit superior antifouling properties to resist protein adsorption and cell adhesion. Further analysis shows a linear inversion correlation between elastic modulus and protein adsorption of pSBMA hydrogels, i.e., the hydrogel with the higher elastic modulus exhibits the lower protein adsorption (the better antifouling property). This work not only provides a simple thermal-pretreatment strategy for fabricating pSBMA hydrogels, but also demonstrates multifunctional properties of the pSBMA hydrogels, which possess a great potential to fulfill some biomedical applications.

3D Scaffolds Based on Conductive Polymers for Biomedical Applications

3D scaffolds appear to be a cost-effective ultimate answer for biomedical applications, facilitating rapid results while providing an environment similar to in vivo tissue. These biomaterials offer large surface areas for cell or biomaterial attachment, proliferation, biosensing and drug delivery applications. Among 3D scaffolds, the ones based on conjugated polymers (CPs) and natural nonconductive polymers arranged in a 3D architecture provide tridimensionality to cellular culture along with a high surface area for cell adherence and proliferation as well electrical conductivity for stimulation or sensing. However, the scaffolds must also obey other characteristics: homogeneous porosity, with pore sizes large enough to allow cell penetration and nutrient flow; elasticity and wettability similar to the tissue of implantation; and a suitable composition to enhance cell-matrix interactions. In this Review, we summarize the fabrication methods, characterization techniques and main applications of conductive 3D scaffolds based on conductive polymers. The main barrier in the development of these platforms has been the fabrication and subsequent maintenance of the third dimension due to challenges in the manipulation of conductive polymers. In the last decades, different approaches to overcome these barriers have been developed for the production of conductive 3D scaffolds, demonstrating a huge potential for biomedical purposes. Finally, we present an overview of the emerging strategies developed to manufacture 3D conductive scaffolds, the techniques used to fully characterize them, and the biomedical fields where they have been applied.