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The fabrication and characterization of a hydrogel-based conductometric sensor have been carried out. The purpose of this research is to fabricate a small robust hydrogel-based conductometric sensor for real-time monitoring of pH in the physiological range.

A pH-responsive Chitosan/Gelatin composite hydrogel has been used for this purpose. This study reports and analyzes the sensing response obtained from four hydrogel compositions with varying Chitosan/Gelatin ratios. The pH-responsive nature of the hydrogel has been mapped out through volumetric and conductometric tests. An attempt has been made to correlate these characteristics with the physico-chemical nature of the hydrogel through scanning electron microscopy, Fourier transform infrared spectroscopy and X-ray diffraction techniques.

The four hydrogel compositions differed on the basis of gel composition ratios; the conductometric analysis results prove that the sensor with the hydrogel composition (Chitosan 2 per cent, Gelatin 7 per cent, ratio 1:2) produces the best pH resolution in the pH range of 4 to 9. The sensing mechanisms and the differences obtained between individual sensor outputs have been discussed in detail. On the basis of this extensive in vitro assessment, it has been concluded that while key pendant functional groups contribute to pH-responsive characteristics of the hydrogel, the overall sensitivity of the sensors gel component to surrounding pH is also determined by the crystalline to amorphous ratio of the hydrogel composite, its interpenetrating cross-linked structure and the relative ratio of the hydrophilic to the pH-sensitive components.

The conductometric sensor results prove that the fabricated sensor with the shortlisted hydrogel composition shows good sensitivity in the physiological pH range (4 to 9) and it has the potential for use in point of care medical devices for diagnostic purposes.

This is the first reported version of the fabrication and testing and analysis/comparison of a hydrogel-based conductometric sensor based on this composition. The work is original and has not been replicated anywhere.

The purpose of this paper is to present synthesis protocol of hydrogel composed of Chitosan (CS) and Poly(ethylene glycol) (PEG) and establish an understanding of its thermal responsive behavior. It aims to prove the basic temperature sensing ability of a novel CS-PEG-based hydrogel and define its sensing span.

This study includes synthesis of CS and PEG-based hydrogel samples by first performing dissolution of both constituents, respectively, and then adding Glutaraldehyde as the cross-linking agent. It further includes proposed hydrogel’s swelling studies and dynamic behavior testing, followed by hydrogel characterization by Fourier transform infrared spectroscopy, X-ray diffraction and SEM. The last section focuses on the use of proposed hydrogel as a temperature sensor.

Detailed experimental results show that a hydrogel comprising of CS and PEG presents a thermally responsive behavior. It offers potential to be used as a temperature responsive hydrogel-based sensor which could be used in medical applications.

This research study presents scope for future research in the field of thermally responsive bio-sensors. It provides basis for the fabrication of a thermal responsive sensor system based on hydrogels that can be used in specific medical applications.

Real-time monitoring of wound or injured tissues is critical for speedy recovery, and the onset of a cascade of biochemical reactions provides potential biomarkers that facilitate the process of wound monitoring, e.g. pH, temperature, moisture level, bacterial load, cytokines, interleukins, etc. Among all the biomarkers, pH has been known to have a profound impact on the wound healing process, and is used to determine the incidence of bacterial infection of the wound (persistently elevated alkaline pH), proteolytic activity at the site of injury, take rate in skin grafting, wound healing stage and preparation for wound debridement.

This review highlights the significance of pH in determination of clinical parameters and for selection of an appropriate treatment regime, and it presents an in-depth analysis of the designs and fabrication methods that use integrated pH sensors, which have been reported to date for the real-time monitoring of wound healing.

For an expedited wound healing process, the significance of pH mandated the need of an integrated sensor system that would facilitate real-time monitoring of healing wounds and obviate the requirement of redressing or complicated testing procedures, which are both labor-intensive and painful for the patient. The review also discussed different types of sensor systems which were developed using hydrogel as a pH-responsive system coupled with voltammetry, potentiometry, impedimetric and flex-circuit inductive transducer systems. All of the mentioned devices have considerable potential for clinical applications, and there is need of in vivo testing to validate their efficiency and sensitivity under practical scenarios.

This manuscript is an original review of literature, and permission has been granted to use the figures from previously published papers.