Electrode surface rebuilding for electrochemical assembling of conductive PEDOT:PSS hydrogel towards biosensing

Design of a microneedle-based enzyme biosensor using a simple and cost-effective electrochemical strategy to monitor superoxide anion released from cancer cells

Early detection of Reactive oxygen species (ROS) concentration is very important in cancer diagnosis, pathological examinations, and health screening. Studies show that changes in ROS concentration occurs in a short time, causing irreparable damage to living cells and organs. Miniaturized sensors and microelectrodes are capable of online monitoring of electrochemical reactions both in vitro and in vivo. In this study, an enzymatic biosensor based on an electrochemically roughened gold microneedle electrode (RAuME) has been developed to measure superoxide anion released from prostate cancer cells. A uniform layer of reduced graphene oxide (rGO) was deposited onto the gold microelectrode through electrochemical reduction, followed by electrodeposition of yttrium hexacyanoferrate (YHCF) nanoparticles. The deposited layers improved the current response of the microneedle electrode in CV, Impedance, and Amperometric analysis. Furthermore, chitosan was utilized to superoxide dismutase (SOD) immobilization. The presence of chitosan maintained the catalytic properties of the SOD enzyme. The developed microsensor monitored the superoxide anion in a wide linear range from 0.304 to 314 μM with detection limit of 17 nm. According to the physiological concentration of the superoxide anion (10-100 nm), we hypothesized that the developed micro-biosensor can mediate a fast monitoring of ROS that facilitates early-stage cancer diagnosis and treatment.

PEDOTs-Based Conductive Hydrogels: Design, Fabrications, and Applications

Conductive hydrogels combine the benefits of soft hydrogels with electrical conductivity and have gained significant attention over the past decade. These innovative materials, including poly(3,4-ethylenedioxythiophene) (PEDOTs)-based conductive hydrogels (P-CHs), are promising for flexible electronics and biological applications due to their tunable flexibility, biocompatibility, and hydrophilicity. Despite the recent advances, the intrinsic correlation between the design, fabrications, and applications of P-CHs has been mostly based on trial-and-error-based Edisonian approaches, significantly limiting their further development. This review comprehensively examines the design strategies, fabrication technologies, and diverse applications of P-CHs. By summarizing design strategies, such as molecular, network, phase, and structural engineering, and exploring both 2D and 3D fabrication techniques, this review offers a comprehensive overview of P-CHs applications in diverse fields including bioelectronics, soft actuators, energy devices, and solar evaporators. Establishing this critical internal connection between design, fabrication, and application aims to guide future research and stimulate innovation in the field of functional P-CHs, offering broad benefits to multidisciplinary researchers.

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.

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.

Paper-based microfluidics in sweat detection: from design to application

Sweat, as a sample that includes a lot of biochemical information, is good for non-invasive monitoring. In recent years, there have been an increasing number of studies on in situ monitoring of sweat. However, there are still some challenges for the continuous analysis of samples. As a hydrophilic, easy-to-process, environmentally friendly, inexpensive and easily accessible material, paper is an ideal substrate material for making in situ sweat analysis microfluidics. This review introduces the development of paper as a sweat analysis microfluidic substrate material, focusing on the advantages of the structural characteristics of paper, trench design and equipment integration applications to expand the design and research ideas for the development of in situ sweat detection technology.

Preparation and properties of cellulose nanocrystal-based ion-conductive hydrogels

Ion-conductive hydrogels were prepared by a simple one-pot method based on cellulose nanocrystals (CNC) and polyvinyl alcohol (PVA). PVA-CNC hydrogels were prepared with different contents of CNC and Al³⁺ ions to enhance the performance of ion-conductive hydrogels. The samples were characterized by Fourier transform infrared spectroscopy, universal testing machine, LCR digital bridge and scanning electron microscopy analyses. The results show that DMSO solvent can enhance the anti-freezing and moisture retention property of the polyvinyl alcohol hydrogel. With the increase of CNC content in the hydrogels, their mechanical properties are also improved. When the CNC concentration is 0.2 wt%, the maximum tensile strength and elongation at break are 750 KPa and 410.47%, respectively. Compared to the hydrogel without CNC, the tensile strength of the hydrogel with 0.2 wt% CNC was increased to 733% and elongation at break was increased to 236%. However, the mechanical properties of the hydrogel will decrease when the CNC content increases to 0.25 wt%. When the hydrogel is stretched, the relative resistance of the hydrogel increases with the increase of tensile deformation. The hydrogels can also be assembled to form self-powered batteries with a voltage of 0.808 V. This indicates that the hydrogels have potential application value in flexible sensors.

Enhancing Strain-Sensing Properties of the Conductive Hydrogel by Introducing PVDF-TrFE

Conductive hydrogels have attracted attention because of their wide application in wearable devices. However, it is still a challenge to achieve conductive hydrogels with high sensitivity and wide frequency band response for smart wearable strain sensors. Here, we report a composite hydrogel with piezoresistive and piezoelectric sensing for flexible strain sensors. The composite hydrogel consists of cross-linked chitosan quaternary ammonium salt (CHACC) as the hydrogel matrix, poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT: PSS) as the conductive filler, and poly(vinylidene fluoride-co-trifluoroethylene) (PVDF-TrFE) as the piezoelectric filler. A one-pot thermoforming and solution exchange method was used to synthesize the CHACC/PEDOT: PSS/PVDF-TrFE hydrogel. The hydrogel-based strain sensor exhibits very high sensitivity (GF: 19.3), fast response (response time: 63.2 ms), and wide frequency range (response frequency: 5-25 Hz), while maintaining excellent mechanical properties (elongation at break up to 293%). It can be concluded that enhanced strain-sensing properties of the hydrogel are contributed to both greater change in the relative resistance under stress and wider response to dynamic and static stimulus by adding PVDF-TrFE. This has a broad application in monitoring human motion, detecting subtle movements, and identifying object contours and a hydrogel-based array sensor. This work provides an insight into the design of composite hydrogels based on piezoelectric and piezoresistive sensing with applications for wearable sensors.