Browsing by Author "Sharma, Sanjiv"
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- Alzheimer's diagnosis beyond cerebrospinal fluid: Probe-Free Detection of Tau Proteins using MXene based redox systems and molecularly imprinted polymersPublication . Arjum, Ajith Mohan; Deshpande, Sudhaunsh; Dunlop, Tom; Norman, Beth; Oliviera, Daniela; Vulpe, Georgeta; Moreira, Felismina; Sharma, SanjivPhosphorylated Tau proteins are promising biomarkers for the diagnosis and prognosis of Alzheimer's disease. This study presents a novel voltametric sensor using a vanadium MXene polydopamine (VxPDA) redox active composite and a Tau-441-specific polyaniline molecularly imprinted polymer (PANI MIP) for the sensitive detection of Tau-441 in interstitial fluid (ISF) and plasma. The VxPDA/PANI MIP sensor demonstrates a broad detection range of 5 fg/mL to 5 ng/mL (122 aM/L to 122 pM/L) in ISF without the use of redox mediators, with a lower limit of detection (LOD) of 2.3 fg/mL (60 aM/L). Furthermore, a handheld device utilizing this technology successfully detects Tau-441 in artificial serum with high sensitivity (5 fg/mL to 150 fg/mL (122 aM/L to 366 aM/L)) and specificity within a clinically relevant range. The rapid detection time (∼32 min) and low cost (∼£20/device) of this sensor highlight its potential for minimally invasive, early AD diagnosis in clinical settings. This advancement aims to facilitate a transition away from invasive cerebrospinal fluid (CSF)-based diagnostic techniques for AD.
- A cork based substrate coupled with artificial antibodies for point-of-care detection of pro-inflammatory cytokine biomarkersPublication . Correia, Bárbara; Oliveira, Daniela; Vulpe, Georgeta; Tavares, Ana P. M.; Sales, M. Goreti F.; Duarte, Abel J.; Sharma, Sanjiv; Moreira, Felismina T. C.Whilst single use point of care testing (PoCT) devices have transformed healthcare globally, there are major concerns over their environmental consequences. These concerns could be addressed by employing devices made of environmentally friendly materials. Herein, we report on the use of cork based PoCT devices. Cork is known to be fully biodegradable and can be easily recycled without producing toxic residues. We report on how a cork-based substrate coupled with a molecularly imprinted polymer (MIP) that serves as an “artificial antibody” can be used for point-of-care testing of the pro-inflammatory biomarker interleukin 6 (IL-6). The featured PoCT device has an electrochemical transducer that provides the desired clinical dynamic range for blood and can measure concentrations as low as 1 pg mL−1, indicating its usefulness in point of care measurements for monitoring pathological disorders, worldwide. In addition, it has a huge environmental impact as it can reduce the waste generated by other polymeric/ceramic carriers used for the same purpose.
- Detection of cardiac biomarker proteins using a disposable based on a molecularly imprinted polymer grafted onto graphitePublication . Moreira, Felismina T. C.; Sharma, Sanjiv; Dutra, Rosa A.F.; Noronha, João P. C.; Cass, Anthony E. G.; Sales, M. Goreti F.A low-cost disposable was developed for rapid detection of the protein biomarker myoglobin (Myo) as a model analyte. A screen printed electrode was modified with a molecularly imprinted material grafted on a graphite support and incorporated in a matrix composed of poly(vinyl chloride) and the plasticizer o-nitrophenyloctyl ether. The protein-imprinted material (PIM) was produced by growing a reticulated polymer around a protein template. This is followed by radical polymerization of 4-styrenesulfonic acid, 2-aminoethyl methacrylate hydrochloride, and ethylene glycol dimethacrylate. The polymeric layer was then covalently bound to the graphitic support, and Myo was added during the imprinting stage to act as a template. Non-imprinted control materials (CM) were also prepared by omitting the Myo template. Morphological and structural analysis of PIM and CM by FTIR, Raman, and SEM/EDC microscopies confirmed the modification of the graphite support. The analytical performance of the SPE was assessed by square wave voltammetry. The average limit of detection is 0.79 μg of Myo per mL, and the slope is −0.193 ± 0.006 μA per decade. The SPE-CM cannot detect such low levels of Myo but gives a linear response at above 7.2 μg · mL−1, with a slope of −0.719 ± 0.02 μA per decade. Interference studies with hemoglobin, bovine serum albumin, creatinine, and sodium chloride demonstrated good selectivity for Myo. The method was successfully applied to the determination of Myo urine and is conceived to be a promising tool for screening Myo in point-of-care patients with ischemia.
- 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.
- 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.
- Protein-responsive polymers for point-of-care detection of cardiac biomarkerPublication . Moreira, Felismina T. C.; Sharma, Sanjiv; Dutra, Rosa A.F.; Noronha, João P. C.; Cass, Anthony E. G.; Sales, M. Goreti F.This work describes a novel use for the polymeric film, poly(o-aminophenol) (PAP) that was made responsive to a specific protein. This was achieved through templated electropolymerization of aminophenol (AP) in the presence of protein. The procedure involved adsorbing protein on the electrode surface and thereafter electroploymerizing the aminophenol. Proteins embedded at the outer surface of the polymeric film were digested by proteinase K and then washed away thereby creating vacant sites. The capacity of the template film to specifically rebind protein was tested with myoglobin (Myo), a cardiac biomarker for ischemia. The films acted as biomimetic artificial antibodies and were produced on a gold (Au) screen printed electrode (SPE), as a step towards disposable sensors to enable point-of-care applications. Raman spectroscopy was used to follow the surface modification of the Au-SPE. The ability of the material to rebind Myo was measured by electrochemical techniques, namely electrochemical impedance spectroscopy (EIS) and square wave voltammetry (SWV). The devices displayed linear responses to Myo in EIS and SWV assays down to 4.0 and 3.5 μg/mL, respectively, with detection limits of 1.5 and 0.8 μg/mL. Good selectivity was observed in the presence of troponin T (TnT) and creatine kinase (CKMB) in SWV assays, and accurate results were obtained in applications to spiked serum. The sensor described in this work is a potential tool for screening Myo in point-of-care due to the simplicity of fabrication, disposability, short time response, low cost, good sensitivity and selectivity.
- Smart Plastic Antibody Material (SPAM) tailored on disposable screen printed electrodes for protein recognition: application to Myoglobin detectionPublication . Moreira, Felismina T. C.; Sharma, Sanjiv; Dutra, Rosa A.F.; Noronha, João P. C.; Cass, Anthony E. G.; Sales, M. Goreti F.This work introduces two major changes to the conventional protocol for designing plastic antibodies: (i) the imprinted sites were created with charged monomers while the surrounding environment was tailored using neutral material; and (ii) the protein was removed from its imprinted site by means of a protease, aiming at preserving the polymeric network of the plastic antibody. To our knowledge, these approaches were never presented before and the resulting material was named here as smart plastic antibody material (SPAM). As proof of concept, SPAM was tailored on top of disposable gold-screen printed electrodes (Au-SPE), following a bottom-up approach, for targeting myoglobin (Myo) in a point-of-care context. The existence of imprinted sites was checked by comparing a SPAM modified surface to a negative control, consisting of similar material where the template was omitted from the procedure and called non-imprinted materials (NIMs). All stages of the creation of the SPAM and NIM on the Au layer were followed by both electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). AFM imaging was also performed to characterize the topography of the surface. There are two major reasons supporting the fact that plastic antibodies were effectively designed by the above approach: (i) they were visualized for the first time by AFM, being present only in the SPAM network; and (ii) only the SPAM material was able to rebind to the target protein and produce a linear electrical response against EIS and square wave voltammetry (SWV) assays, with NIMs showing a similar-to-random behavior. The SPAM/Au-SPE devices displayed linear responses to Myo in EIS and SWV assays down to 3.5 μg/mL and 0.58 μg/mL, respectively, with detection limits of 1.5 and 0.28 μg/mL. SPAM materials also showed negligible interference from troponin T (TnT), bovine serum albumin (BSA) and urea under SWV assays, showing promising results for point-of-care applications when applied to spiked biological fluids.
- 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.