Emma P. Córcoles

Cotton fabric-based electrochemical device for lactate measurement in saliva

Lactate measurement is vital in clinical diagnostics especially among trauma and sepsis patients. In recent years, it has been shown that saliva samples are an excellent applicable alternative for non-invasive measurement of lactate. In this study, we describe a method for the determination of lactate concentration in saliva samples by using a simple and low-cost cotton fabric-based electrochemical device (FED). The device was fabricated using template method for patterning the electrodes and wax-patterning technique for creating the sample placement/reaction zone. Lactate oxidase (LOx) enzyme was immobilised at the reaction zone using a simple entrapment method. The LOx enzymatic reaction product, hydrogen peroxide (H2O2) was measured using chronoamperometric measurements at the optimal detection potential (-0.2 V vs. Ag/AgCl), in which the device exhibited a linear working range between 0.1 to 5 mM, sensitivity (slope) of 0.3169 μA mM(-1) and detection limit of 0.3 mM. The low detection limit and wide linear range were suitable to measure salivary lactate (SL) concentration, thus saliva samples obtained under fasting conditions and after meals were evaluated using the FED. The measured SL varied among subjects and increased after meals randomly. The proposed device provides a suitable analytical alternative for rapid and non-invasive determination of lactate in saliva samples. The device can also be adapted to a variety of other assays that requires simplicity, low-cost, portability and flexibility.

Nanoporous silicon as drug delivery systems for cancer therapies

Porous silicon nanoparticles have been established as excellent candidates for medical applications as drug delivery devices, due to their excellent biocompatibility, biodegradability, and high surface area. The simple fabrication method by electrochemical anodization of silicon and its photoluminescent properties are some of the merits that have contributed to the increasing interest given to porous silicon. This paper presents the methods of fabrication, which can be customized to control the pore size, various chemical treatments used for the modification of silicon surfaces, and the characterization and pore morphology of silicon structures. Different approaches used for drug loading and the variety of coatings used for the controlled released are revised. The monitoring of the toxicity of silicon degradation products and the in vivo release of a drug in a specific site are described taking into account its significance on medical applications, specifically on cancer therapy.

Saliva-Based Biosensors: Noninvasive Monitoring Tool for Clinical Diagnostics

Saliva is increasingly recognised as an attractive diagnostic fluid. The presence of various disease signalling salivary biomarkers that accurately reflect normal and disease states in humans and the sampling benefits compared to blood sampling are some of the reasons for this recognition. This explains the burgeoning research field in assay developments and technological advancements for the detection of various salivary biomarkers to improve clinical diagnosis, management, and treatment. This paper reviews the significance of salivary biomarkers for clinical diagnosis and therapeutic applications, with focus on the technologies and biosensing platforms that have been reported for screening these biomarkers.

Cotton fabric as an immobilization matrix for low-cost and quick colorimetric enzyme-linked immunosorbent assay (ELISA)

Enzyme-linked immunosorbent assay (ELISA) is a reliable quantification assay used in laboratories around the world. The method itself is time consuming and requires a relatively high volume of reagents. In recent years, microfluidics based on paper platforms has been used extensively to develop devices for point of care diagnosis testing. In this work, cloth was used as a superior alternative to paper (stronger, higher controllable rates for fluid mixing and lower environmental impact) to implement ELISA and quantitatively determine human chorionic gonadotropin. The intrinsic properties of cotton fabric allowed the entrapment of the antibody through cloth fibers and showed a superior alternative to common immobilization procedures. The cloth-based ELISA was shown to be feasible to detect human chorionic gonadotropin (0–140 × 10−6 nmol) via image analysis providing a sigmoid fit (R2 = 0.983) of the data and a limit of detection (LOD) of 2.19 ng mL−1. Both the volume of the reagents and the time required for the assay were effectively reduced compared with conventional ELISA. Ultimately, this user-friendly device can potentially be embedded in bandages and gauzes for surgical and clinical settings or in clothing for home care monitoring of elderly and chronic patients.

Monitoring magnesium degradation using microdialysis and fabric-based biosensors

This paper describes the development of a monitoring system capable of detecting the concentration of magnesium ions (Mg2+) released during the degradation of magnesium implants. The system consists of a microdialysis probe that samples fluid adjacent to the implant and a catalytic biosensor specific to Mg2+ ions. The biosensor was fabricated on a cotton fabric platform, in which a mixture of glycerol kinase and glycerol-3-phosphate oxidase enzymes was immobilized on the fabric device via a simple matrix entrapment technique of the cotton fibers. Pure magnesium was used as the implant material. Subsequently, the concentration of ions released from the degradation of the magnesium specimen in Ringer’s solution was evaluated using cyclic voltammetry technique. The device demonstrated a pseudo-linear response from 0.005 to 0.1 mmol L−1 with a slope of 67.48 μA mmol−1 L. Detectable interfering species were lesser than 1% indicating a high selectivity of the fabric device. Furthermore, the device requires only 3 μL of fluid sample to complete the measurement compared to spectroscopic method (±50 μL), hence providing a higher temporal resolution and reduced sampling time. The system could potentially provide a real time assessment of the degradation behavior, a new studied aspect in biodegradable metals research.

The Need for Invasive Sensing

The fast progress in medicinal therapies, clinical instrumentation and drugs development have contributed paradoxically to higher demand for patient monitoring in healthcare systems. The higher increase in chronic patients and an aging population has led to the use of intensive and invasive methods in general wards areas, which otherwise were reserved for patients in high level of care environments, such as intensive care units.

Conclusion and Future Trends

With the advance in nanotechnology and the use of materials such as silicon and CNT with excellent mechanical, optical and electrochemical properties, the factor that prevents the widespread use of implantable devices for clinical monitoring is their low reliability.

Progress in Sensor Biocompatibility

Two main approaches have been followed to improve sensors biocompatibility: elimination of biological responses by means of coatings and surface modifications, and substance releasing sensors that increase this biological response further.

Further Information and Advice

Research in implantable devices is progressing at a fast rate. Glucose implantable devices are at the forefront of this technology due to the high demand for diabetes management. Diabetes research news, blogs and website links present some of the latest commercialised or in process of being commercialised technology.

Microdialysis Probe Requirements

Materials such as cellulose, cuprophane and hospal were extensively used to fabricate MD membranes, since chemical composition was considered to play an important role in the in vitro recovery. Commercially available clinical probes are now being fabricated with supported polycrystalline, polyethylene terephthalate (PET) membranes with specific weight cut-off, typically of 20 kDa and 1 MDa in case of macromolecules studies.