Construction of an amperometric TG biosensor based on AuPPy nanocomposite and poly (indole-5-carboxylic acid) modified Au electrode

Development and Evaluation of a Low-Cost Triglyceride Quantification Enzymatic Biosensor Using an Arduino-Based Microfluidic System

Overweight and obesity promote diabetes and heart disease onset. Triglycerides are key biomarkers for cardiovascular disease, strokes, and other health issues. Scientists have devised methods and instruments for the detection of these molecules in liquid samples. In this study, an enzymatic biosensor was developed using an Arduino-based microfluidic platform, wherein a lipolytic enzyme was immobilized on an ethylene-vinyl acetate polymer through physical adsorption. This low-cost optical biosensor employed a spectrophotometric transducer and was assessed in liquid samples to indirectly detect triglycerides and fatty acids using p-nitrophenol as an indicator. The average triglyceride level detected in the conducted experiments was 47.727 mg/dL. The biosensor exhibited a percentage of recovery of 81.12% and a variation coefficient of 0.791%. Furthermore, the biosensor demonstrated the ability to detect triglyceride levels without the need for sample dilution, ranging from 7.6741 mg/dL to 58.835 mg/dL. This study successfully developed an efficient and affordable enzymatic biosensor prototype for triglyceride and fatty acid detection. The lipolytic enzyme immobilization on the polymer substrate provided a stable and reproducible detection system, rendering this biosensor an exciting option for the detection of these molecules.

Boosting the Electrochemical Performance of PI-5-CA/C-SWCNT Nanohybrid for Sensitive Detection of E. coli O157:H7 From the Real Sample

Redox activity is an important indicator for evaluating electrochemical biosensors. In this work, we have successfully polymerized indole-5-carboxylic acid into poly-5-carboxyindole nanomaterials (PI-5-CA), using its superior redox activity, and introduced carboxylated single-walled carbon nanotubes (C-SWCNTs) to synthesize a composite material. Finally, a synthesized composite material was used for the modification of the glass carbon electrode to fabricate the PI-5-CA/C-SWCNTs/GCE-based immunosensor and was successfully applied for the sensitive detection of E. coli O157:H7. The fabricated immunosensor exhibited an outstanding electrocatalytic activity toward the detection of E. coli O157:H7 with a remarkably lowest limit of detection (2.5 CFU/ml, LOD = 3 SD/k, n = 3) and has a wide linear range from 2.98×101 to 2.98×107 CFU/ml. Inspired from the excellent results, the fabricated electrode was applied for the detection of bacteria from real samples (water samples) with a good recovery rate (98.13–107.69%) as well as an excellent stability and specificity. Owing to its simple preparation, excellent performance, and detection time within 30 min, our proposed immunosensor will open a new horizon in different fields for the sensitive detection of bacteria from real samples.

Organic Polymer and Metal Nano-particle Based Composites for Improvement of the Analytical Performance of Electrochemical Biosensors

Metal nanoparticles (NPs) are described in the nanoscale and made from either pure metals or their compounds such as oxides. Metallic NPs have certain indistinct functional groups due to which these can bind with any type of ligand, antibody and drugs. Organic polymers, which conduct electricity, are called conducting polymers (intrinsically conducting polymers). They behave like semiconductors by exhibiting metallic conductivity. Process-ability is the major advantage of conducting polymers. Nanocomposite is a novel material having nano-fillers scattered in a matrix with morphology and interfacial characteristics of nano-composites including their individual property that influence their characteristics. Conducting polymers and NP composites can enhance the rate of electron transport between the current collector material (electrode) and the electrolyte; therefore they have been employed in the construction of improved electrochemical sensors such as amperometric, catalytic and potentiodynamic affinity sensors.

Construction of a Hydrogel Pectin-Based Triglyceride Optical Biosensor with Immobilized Lipase Enzymes

A novel and simple optical biosensor to detect triglycerides (TGs) has been successfully constructed by using pectin hydrogel membrane as the indicator pH and chromoionophore ETH 5294 (CI), with lipase as the catalyst. The enzymatic working system against TGs releasing H⁺ ions will affect the color absorbance of CI. The characterization results show that a TG biosensor has the optimum condition and sensitivity at the phosphate buffer concentration of 50 mM, pH 7, and enzyme loading of 60 μg. The biosensor works at the tripalmitin (TP) concentration range of 100–400 mg/dL. With the sensitivity of 0.001 (∆A/(mg/dL)), the biosensor response reaches stability after five minutes, and the limit of detection (LOD) of the TG optical biosensor is 15 mg/dL. Relative standard deviation (RSD) in a reproducibility test was 2.5%, with a 15-day lifespan.

A new multienzyme-type biosensor for triglyceride determination

An amperometric multienzyme biosensor for determination of triglycerides (TGs) was constructed by mounting three gelatin membrane-bound enzymes on a glassy carbon electrode (working electrode), then connecting it to electrometer along with an Ag/AgCl reference electrode and a Pt auxiliary electrode. Characterization and optimization of the multienzyme biosensor, which is prepared with glycerol kinase (GK) (E.C.2.7.1.30), glycerol-3-phosphate oxidase (GPO) (EC 1.1.3.21), and lipase (EC 3.1.1.3), were studied. In the optimization studies for the bioactive layer components of the prepared biosensor, the optimum amounts of gelatin, bovine serum albumin (BSA), and glutaraldehyde was calculated as 1 mg/cm(2), 1 mg/cm(2), and 2.5%, respectively. Optimum pH and temperature of the reaction of biosensor were determined as 7.0 and 40 °C, respectively. Linear range of triolein for the biosensor was found from the calibration curve between several substrate concentration and Δ Current. After optimization and characterization of the biosensor, its operationability in triglycerides was also tested.

Biosensing Test-Bed Using Electrochemically Deposited Reduced Graphene Oxide

The development of an efficient test-bed for biosensors requires stable surfaces, capable of interacting with the functional groups present in bioentities. This work demonstrates the formation of highly stable electrochemically reduced graphene oxide (ERGO) thin films reproducibly on indium tin oxide (ITO)-coated glass substrates using a reliable technique through 60 s chronoamperometric reduction of a colloidal suspension maintained at neutral pH containing graphene oxide in deionized water. Structural optimization and biocompatible interactions of the resulting closely packed and uniformly distributed ERGO flakes on ITO surfaces (ERGO/ITO) are characterized using various microscopic and spectroscopic tools. Lipase enzyme is immobilized on the ERGO surface in the presence of ethyl-3-[3-(dimethylamino)propyl]carbodimide and N-hydroxysuccinimide for the detection of triglyceride in a tributyrin (TBN) solution. The ERGO/ITO surfaces prepared using the current technique indicate the noticeable detection of TBN, a source of triglycerides, at a sensitivity of 37 pA mg dL(-1) cm(-2) in the linear range from 50 to 300 mg dL(-1) with a response time of 12 s. The low apparent Michaelies-Menten constant of 0.28 mM suggests high enzyme affinity to TBN. The currently developed fast, simple, highly reproducible, and reliable technique for the formation of an ERGO electrode could be routinely utilized as a test bed for the detection of clinically active bioentities.

Rational Design of Nanoparticle Platforms for "Cutting-the-Fat": Covalent Immobilization of Lipase, Glycerol Kinase, and Glycerol-3-Phosphate Oxidase on Metal Nanoparticles

The aggregates of nanoparticles (NPs) are considered better supports for the immobilization of enzymes, as these promote enzyme kinetics, due to their unusual but favorable properties such as larger surface area to volume ratio, high catalytic efficiency of certain immobilized enzymes, non-toxicity of some of the nanoparticle matrices, high stability, strong adsorption of the enzyme of interest by a number of different approaches, and faster electron transportability. Co-immobilization of multiple enzymes required for a multistep reaction cascade on a single support is more efficient than separately immobilizing the corresponding enzymes and mixing them physically, since products of one enzyme could serve as reactants for another. These products can diffuse much more easily between enzymes on the same particle than diffusion from one particle to the next, in the reaction medium. Thus, co-immobilization of enzymes onto NP aggregates is expected to produce faster kinetics than their individual immobilizations on separate matrices. Lipase, glycerol kinase, and glycerol-3-phosphate oxidase are required for lipid analysis in a cascade reaction, and we describe the co-immobilization of these three enzymes on nanocomposites of zinc oxide nanoparticles (ZnONPs)-chitosan (CHIT) and gold nanoparticles-polypyrrole-polyindole carboxylic acid (AuPPy-Pin5COOH) which are electrodeposited on Pt and Au electrodes, respectively. The kinetic properties and analytes used for amperometric determination of TG are fully described for others to practice in a trained laboratory. Cyclic voltammetry, scanning electron microscopy, Fourier transform infra-red spectra, and electrochemical impedance spectra confirmed their covalent co-immobilization onto electrode surfaces through glutaraldehyde coupling on CHIT-ZnONPs and amide bonding on AuPPy/Pin5COOH. The combined activities of co-immobilized enzymes was tested amperometrically, and these composite nanobiocatalysts showed optimum activity within 4-5s, at pH 6.5-7.5 and 35°C, when polarized at a potential between 0.1 and 0.4V. Co-immobilized enzymes showed excellent linearity within 50-700mg/dl of the lipid with detection limit of 20mg/dl for triolein. The half life of co-immobilized enzymes was 7 months, when stored dry at 4°C which is very convenient for practical applications. Co-immobilized biocatalysts measured triglycerides in the sera of apparently healthy persons and persons suffering from hypertriglyceridemia, which is recognized as a leading cause for heart disease. The measurement of serum TG by co-immobilized enzymes was unaffected by the presence of a number of serum substances, tested as potential interferences. Thus, co-immobilization of enzymes onto aggregates of NPs resulted in improved performance for TG analysis.

A nanostructured conductive hydrogels-based biosensor platform for human metabolite detection

The development of a scalable, low-cost, and versatile biosensor platform for the sensitive and rapid detection of human metabolites is of great interest for healthcare, pharmaceuticals, and medical science. On the basis of hierarchically nanostructured conducting polymer hydrogels, we designed a flexible biosensor platform that can detect various human metabolites, such as uric acid, cholesterol, and triglycerides. Owing to the unique features of conducting polymer hydrogels, such as high permeability to biosubstrates and rapid electron transfer, our biosensors demonstrate excellent sensing performance with a wide linear range (uric acid, 0.07-1 mM; cholesterol, 0.3-9 mM, and triglycerides, 0.2-5 mM), high sensitivity, low sensing limit, and rapid response time (∼3 s). Given the facile and scalable processability of hydrogels, the proposed conductive hydrogels-based biosensor platform shows great promise as a low-cost sensor kit for healthcare monitoring, clinical diagnostics, and biomedical devices.

Bioelectrocatalytic sensor for triglycerides in human skin sebum based on enzymatic cascade reaction of lipase, glycerol kinase and glycerophosphate oxidase

We report the development of an electrochemical biosensor for the quantification of triglycerides in human skin sebum, based on a multienzyme cascade reaction. The presence of excessive triglycerides in human sebum is one of the leading causes of various skin ailments. However, to the best of our knowledge, no bioelectrocatalytic approach for the quantification of sebum triglycerides has been made. In order to develop triglyceride biosensor, we fabricated a multienzyme-associated electrode incorporating lipase, glycerol kinase, and glycerophosphate oxidase. Enzymes were deposited by electrostatic force and further stabilized via crosslinking between enzymes and polymer matrices. The enzyme-modified biosensing electrode maintained its bioelectrocatalytic activity for five days. An additional constraint was the limited solubility of sebum triglycerides in aqueous electrolytes, impeding the analysis. To address this issue, triglyceride samples were prepared in the form of micelles, enabling efficient sample preparation for biosensor signaling. Calibration tests revealed that the designed assay had a detection range of 15-200mg/dL of micellar triglyceride, which covered the required determination range. The developed biosensing approach was successfully used to determine triglyceride concentrations in real sebum samples of unknown triglyceride content.