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- Flexible 2D and 3D conductive hydrogel platforms for wearable applicationsPublication . Aguiar, Leonor; Pereira, Raquel; Sharma, Sanjiv; Martins, GabrielaHydrogels have risen as exceptionally promising support materials in the development of novel wearable electronic devices. Their remarkable biocompatibility coupled with customizable mechanical features make these biomaterials ideal choices for applications involving direct contact with biological tissues. In this study, a simple and straightforward manufacturing process using bio-sourced polysaccharide chitosan (Chi) was employed for the fabrication of flexible and transparent biopolymeric membranes. Subsequently, this two-dimensional (2D) platform was made conductive, through a one-step process, by utilizing an optimized ratio of chitosan, lactic acid, and silver nanowires (Chi-LaA-AgNWs) dispersion. These electrodes were produced by screen printing technique. Furthermore, a solvent casting technique employing inverse polydimethylsiloxane (PDMS) molds was used to fabricate mechanically stable chitosan microneedles (Chi-MNs). These three dimensional (3D) structures were enriched with a carbon-based ink during the casting of concentrated Chi hydrogels into the mold while utilizing centrifugal forces. The electrochemical properties of the fabricated 2D and 3D conductive platforms were evaluated through cyclic voltammetry (CV). Along this study, the water swelling properties of Chi hydrogels were investigated by incorporating natural crosslinkers and plasticizing compounds like citric acid, glycerol, and sorbitol. Optimization of fabrication, physico-chemical and morphological analysis of the membranes and MNs were also performed. Ultimately, the use of Chi combined with environmentally friendly agents enabled the fabrication of flexible conductive platforms holding good stability, uniformity, and desirable electrical attributes.
- Transdermal electrochemical sensing: Combining microneedles with molecularly imprinted polymers for point-of-care testingPublication . Oliveira, Daniela; Correia, Bárbara P.; Sharma, Sanjiv; Moreira, Felismina T.C.Biomarkers from interstitial skin fluid (ISF) complement conventional biofluids for point-of-care testing and real-time monitoring. In this study, we propose a new approach that combines microneedle technology with molecularly imprinted polymers to improve transdermal electrochemical sensing. The molecularly imprinted polymer, which acts like a plastic antibody, is easy to synthesis and scalable, offering a low detection limit and rapid measurement (20 minutes). It detects IL -6, a proinflammatory cytokine associated with several clinical conditions, including neurological disease and pneumonia caused by SARS-CoV-2. The transdermal sensors successfully identified IL -6 in simulated skin ISF at very low concentrations (1 pg/mL). This breakthrough enables affordable and bloodless testing, facilitating access to point-of-care testing worldwide. The integration of molecularly imprinted polymers and microneedle arrays is very promising for efficient transdermal electrochemical sensing that could find application in various clinical scenarios.
- Molecular Imprinted Polymers on Microneedle Arrays for Point of Care Transdermal Sampling and Sensing of Inflammatory BiomarkersPublication . Oliveira, Daniela; Correia, Barbara P; Sharma, Sanjiv; Moreira, FelisminaThe skin interstitial fluid (ISF) contains biomarkers that complement other biofluids such as blood, sweat, saliva, and urine. It can be sampled in a minimally invasive manner and used either for point of care testing or real time, continuous monitoring of analytes, the latter using microneedle arrays. The analytes present in the skin ISF are indicative of both systemic and local (i.e., skin) physiology. In this paper, we describe combining microneedle technology with molecularly imprinted polymers to demonstrate the potential of transdermal electrochemical sensing. The molecularly imprinted polymer employed here is easy to produce; it can be thought of as plastic antibody. Its synthesis is scalable, and the resulting sensor has a short measurement time (6 min), with high accuracy and a low limit of detection. It provides the requisite specificity to detect the proinflammatory cytokine IL6. IL-6 is present in the skin ISF with other cytokines and is implicated in many clinical states including neurodegenerative diseases and fatal pneumonia from SARSCoV 2. The ability to mass produce microneedle arrays and plastic antibodies will allow for low-cost transdermal sensing devices. The transdermal sensors were able to detect IL-6 at concentrations as low as 1 pg/mL in artificial skin ISF, indicating its utility for routine point of care, bloodless measurements in simpler settings, worldwide.