Polyaniline/MWCNTs/starch modified carbon paste electrode for non-enzymatic detection of cholesterol: application to real sample (cow milk)

Fabrication of natural enzyme-covered / amino-modified Pd-Pt bimetallic-doped zeolitic imidazolate framework for ultrasensitive detection of metabolites

The present article introduced an natural enzyme-covered/amino-modified Pd-Pt bimetallic-doped zeolitic imidazolate framework (NAPPZ) for ultrasensitive and specific detection of glucose. The dodecahedral nanomaterial zeolitic imidazolate framework (ZIF-8)-loaded Pd-Pt bimetallic nanoparticles endowed the composite with peroxidase-like activity. The modification with glucose oxidase (GOx) facilitated the rapid access of H2O2 produced through glucose oxidation to the Pd-Pt nanoparticles vicinity reducing diffusion. GOx specifically catalyzes the transformation of glucose into H2O2, which then H2O2 rapidly migrates to the Pd-Pt nanoparticles, catalyzing the oxidation of colorless o-phenylenediamine into the orange-yellow product 2,3-diaminophenazine. Based on the aforementioned cascade reaction, the NAPPZ and NAPPZ based on ChOx were utilized for detecting glucose in human urine samples and cholesterol in milk, respectively. The NAPPZ strategy presented a broad detection range (20-1100 μmol L-1) and a low detection limit (15.9 μmol L-1) for glucose, and the NAPPZ based on ChOx strategy approach offered a broad detection range (10-500 μmol L-1) and low detection limit (6.4 μmol L-1) for cholesterol. Therefore, this novel method holds significant potential in the areas of clinical diagnostics and food safety.

A hybrid catalyst-triggered cascade reaction for cholesterol detection using a smartphone-based miniature fluorescent apparatus

A new hybrid biological-chemical catalyst, magnetic nanoparticles functionalized with cholesterol oxidase (Fe3O4/APTES/ChOx), was developed for cholesterol detection. In the presence of cholesterol, the enzyme produced H2O2, which facilitated the generation of fluorescent molecules from the fluorogenic substrate with the assistance of Fe3O4 nanoparticles. A smartphone camera with a miniature fluorescent apparatus was used to assess fluorescence emission. Then, a smartphone application was employed to translate the fluorescence intensity to the red, green, and blue (RGB) domain. The developed approach achieved excellent selectivity and acceptable performances while supporting an onsite analysis approach. The practical operational range spanned from 5 to 100 nM, with a detection limit of 0.85 nM. Fe3O4/APTES/ChOx was applied for up to four replicates of reuse and demonstrated stability for at least 30 days. The applicability of the method was evaluated in milk samples, and the results were in accordance with the reference method.

Metal-based non-enzymatic systems for cholesterol detection: mechanisms, features, and performance

Metal based catalysts and electrodes are versatile tools known for their redox properties, catalytic efficiency, and stability under various conditions. Despite the absence of significant scientific hurdles, the utilization of these methods in cholesterol detection, particularly in non-enzymatic approaches, has been relatively underexplored. To this end, there is a pressing need to delve deeper into existing metal-based systems used in non-enzymatic cholesterol sensing, with the goal of fostering the development of innovative practical solutions. Various electrode systems, such as those employing Ni, Ti, Cu, Zn, W, Mn, and Fe, have already been reported for non-enzymatic cholesterol detection, some of them elucidated sensing mechanisms and potential in physiological detection. A detailed mechanistic understanding of oxide-based cholesterol sensors, along with the methodologies for constructing such systems, holds promise of advancing the exploration of practical applications. This review aims to provide a broad perspective on metal oxide systems and their characteristics that are conducive to non-enzymatic cholesterol sensing. It is intended to serve as a springboard with offering a guide to the design and development of efficient and sensitive electrochemical cholesterol sensors.

Macromolecule-Nanoparticle-Based Hybrid Materials for Biosensor Applications

Biosensors function as sophisticated devices, converting biochemical reactions into electrical signals. Contemporary emphasis on developing biosensor devices with refined sensitivity and selectivity is critical due to their extensive functional capabilities. However, a significant challenge lies in the binding affinity of biosensors to biomolecules, requiring adept conversion and amplification of interactions into various signal modalities like electrical, optical, gravimetric, and electrochemical outputs. Overcoming challenges associated with sensitivity, detection limits, response time, reproducibility, and stability is essential for efficient biosensor creation. The central aspect of the fabrication of any biosensor is focused towards forming an effective interface between the analyte electrode which significantly influences the overall biosensor quality. Polymers and macromolecular systems are favored for their distinct properties and versatile applications. Enhancing the properties and conductivity of these systems can be achieved through incorporating nanoparticles or carbonaceous moieties. Hybrid composite materials, possessing a unique combination of attributes like advanced sensitivity, selectivity, thermal stability, mechanical flexibility, biocompatibility, and tunable electrical properties, emerge as promising candidates for biosensor applications. In addition, this approach enhances the electrochemical response, signal amplification, and stability of fabricated biosensors, contributing to their effectiveness. This review predominantly explores recent advancements in utilizing macrocyclic and macromolecular conjugated systems, such as phthalocyanines, porphyrins, polymers, etc. and their hybrids, with a specific focus on signal amplification in biosensors. It comprehensively covers synthetic strategies, properties, working mechanisms, and the potential of these systems for detecting biomolecules like glucose, hydrogen peroxide, uric acid, ascorbic acid, dopamine, cholesterol, amino acids, and cancer cells. Furthermore, this review delves into the progress made, elucidating the mechanisms responsible for signal amplification. The Conclusion addresses the challenges and future directions of macromolecule-based hybrids in biosensor applications, providing a concise overview of this evolving field. The narrative emphasizes the importance of biosensor technology advancement, illustrating the role of smart design and material enhancement in improving performance across various domains.

Tin oxide-polyaniline nanocomposite modified nickel foam for highly selective and sensitive detection of cholesterol in simulated blood serum samples

Cholesterol (CH) is a vital diagnostic marker for a variety of diseases, making its detection crucial in biological applications including clinical practice. In this work, we report the synthesis of tin oxide-polyaniline nanocomposite-modified nickel foam (SnO2-PANI/NF) for non-enzymatic detection of CH in simulated human blood serum. SnO2was synthesized via the hydrothermal method, followed by the synthesis of SnO2-PANI nanocomposite throughin situchemical polymerization of aniline using ammonium persulfate as the oxidizing agent. Morphological studies display agglomerated SnO2-PANI, which possess diameters ranging from an average particle size of ∼50 to ∼500 nm, and the XRD analysis revealed the tetragonal structure of the SnO2-PANI nanocomposite. Optimization studies demonstrating the effect of pH and weight percentage are performed to improve the electrocatalytic performance of the sensor. The non-enzymatic SnO2-PANI/NF sensor exhibits a linear range of 1-100μM with a sensitivity of 300μAμM-1/cm-2towards CH sensing and a low limit of detection of 0.25μM (=3 S m-1). SnO2-PANI/NF facilitates the electrooxidation of CH to form cholestenone by accepting electrons generated during the reaction and transferring them to the nickel foam electrode via Fe (III)/Fe (IV) conversion, resulting in an increased electrochemical current response. The SnO2-PANI/NF sensor demonstrated excellent selectivity against interfering species such as Na+, Cl-, K+, glucose, ascorbic acid, and SO42-. The sensor successfully determined the concentration of CH in simulated blood serum samples, demonstrating SnO2-PANI as a potential platform for a variety of electrochemical-based bioanalytical applications.

An electrochemical microfluidic device for non-enzymatic cholesterol determination using a lab-made disposable electrode

Cholesterol is an important steroid and hormone precursor, and its levels in the blood are associated with risk factors for cardiovascular diseases. In this work, a non-enzymatic methodology for cholesterol determination in serum samples is described. First, a working electrode was constructed using homemade ink and a plastic substrate by a simple dunking process. Next, the dunked electrode (DWE) was modified with nickel ions (Ni-DWE) and combined with a low-cost microfluidic platform, resulting in a thread-based electroanalytical device (μTED). The arrangement of μTED consists of two coupled electrodes (one reference in the inlet reservoir and an auxiliary electrode against the outlet reservoir) and a mobile support for facile working electrode exchange. After optimization of construction parameters, the system was applied for non-enzymatic determination of cholesterol under alkaline conditions using the redox pair Ni(II)/Ni(III) as a mediator. Under the best analytical conditions, a calibration curve was constructed with a linear dynamic range (LDR) from 0.25 to 25.0 μmol L^-1, and the calculated limits of detection (LOD) and quantification (LOQ) were 0.074 and 0.24 μmol L^-1, respectively. No effects of possible interferents on electrochemical response were found in the presence of ascorbic acid, uric acid, dopamine, cysteine, and glucose, suggesting that the proposed device can be used for the determination of cholesterol without significant matrix effects of human plasma. Finally, cholesterol analysis was carried out using spiked plasma samples, and good recovery values were achieved.

Electrochemical devices for cholesterol detection

Cholesterol can be considered as a biomarker of illnesses such as heart and coronary artery diseases or arteriosclerosis. Therefore, the fast determination of its concentration in blood is interesting as a means of achieving an early diagnosis of these unhealthy conditions. Electrochemical sensors and biosensors have become a potential tool for selective and sensitive detection of this biomolecule, combining the analytical advantages of electrochemical techniques with the selective recognition features of modified electrodes. This review covers the different approaches carried out in the development of electrochemical sensors for cholesterol, differentiating between enzymatic biosensors and non-enzymatic systems, highlighting lab-on-a-chip devices. A description of the different modification procedures of the working electrode has been included and the role of the different functional materials used has been discussed.

Emerging Trends in Non-Enzymatic Cholesterol Biosensors: Challenges and Advancements

The development of a highly sensitive and selective non-enzymatic electrochemical biosensor for precise and accurate determination of multiple disease biomarkers has always been challenging and demanding. The synthesis of novel materials has provided opportunities to fabricate dependable biosensors. In this perspective, we have presented and discussed recent challenges and technological advancements in the development of non-enzymatic cholesterol electrochemical biosensors and recent research trends in the utilization of functional nanomaterials. This review gives an insight into the electrochemically active nanomaterials having potential applications in cholesterol biosensing, including metal/metal oxide, mesoporous metal sulfide, conductive polymers, and carbon materials. Moreover, we have discussed the current strategies for the design of electrode material and key challenges for the construction of an efficient cholesterol biosensor. In addition, we have also described the current issues related to sensitivity and selectivity in cholesterol biosensing.

A Comprehensive Review on Biopolymer Mediated Nanomaterial Composites and Their Applications in Electrochemical Sensors

Biopolymers are an attractive green alternative to conventional polymers, owing to their excellent biocompatibility and biodegradability. However, their amorphous and nonconductive nature limits their potential as active biosensor material/substrate. To enhance their bio-analytical performance, biopolymers are combined with conductive materials to improve their physical and chemical characteristics. We review the main advances in the field of electrochemical biosensors, specifically the structure, approach, and application of biopolymers, as well as their conjugation with conductive nanoparticles, polymers and metal oxides in green-based noninvasive analytical biosensors. In addition, we reviewed signal measurement, substrate bio-functionality, biochemical reaction, sensitivity, and limit of detection (LOD) of different biopolymers on various transducers. To date, pectin biopolymer, when conjugated with either gold nanoparticles, polypyrrole, reduced graphene oxide, or multiwall carbon nanotubes forming nanocomposites on glass carbon electrode transducer, tends to give the best LOD, highest sensitivity and can detect multiple analytes/targets. This review will spur new possibilities for the use of biosensors for medical diagnostic tests.

Starch-Based Electrochemical Sensors and Biosensors: A Review

Natural green compounds for sensor modification (binders) are challenging in electrochemistry. Starch is a carbohydrate biopolymer that has been used extensively in the development of biomaterials for the food industry due to its ability to impart textural characteristics and provide gelling or film formation. In particular, the excellent film-forming characteristics have been used for the development of new surface modifying architectures for electrodes. Here, we highlight a very comprehensive overview of the properties of interest of various types of starch in conjunction with (bio)materials in the chemical modification of sensors and biosensors. Throughout the review, we first give an introduction to the extraction, applications, and properties of starches followed by an overview of the prospects and their possible applications in electrochemical sensors and biosensors. In this context, we discuss some important characteristics of starches and different strategies of their film formation with an emphasis on their role in the development of electrochemical sensors and biosensors highlighting their main contributions to enhancing the performance of these devices and their applications in environmental and clinical samples.

Mesoporous NiCo2S4nanoflakes as an efficient and durable electrocatalyst for non-enzymatic detection of cholesterol

The detection of cholesterol is very crucial in clinical diagnosis for rapid and accurate monitoring of multiple disease-biomarkers. There is a great need for construction of a highly reliable and stable electrocatalyst for the efficient detection of cholesterol. In this work, mesoporous NiCo₂S₄nanoflakes of enhanced electrochemical properties are prepared through a facile hydrothermal approach. The developed nanoflakes modified nickel foam electrode exhibits outstanding electrocatalytic properties for the detection of cholesterol with high selectivity. The electrode displays excellent sensitivity of 8623.6μA mM^-1cm^-2, in the wide linear range from 0.01 to 0.25 mM with a low detection limit of 0.01μM. In addition, NiCo₂S₄structure reveals good thermal stability and reproducibility over a period of 8 weeks. Moreover, the nanoflakes show good response for detection of cholesterol in real samples. Our results demonstrate the potential use of NiCo₂S₄as a catalyst for the development of cost-effective electrochemical sensors for medical and industrial applications.

Nano-Scaled Materials and Polymer Integration in Biosensing Tools

The evolution of biosensors and diagnostic devices has been thriving in its ability to provide reliable tools with simplified operation steps. These evolutions have paved the way for further advances in sensing materials, strategies, and device structures. Polymeric composite materials can be formed into nanostructures and networks of different types, including hydrogels, vesicles, dendrimers, molecularly imprinted polymers (MIP), etc. Due to their biocompatibility, flexibility, and low prices, they are promising tools for future lab-on-chip devices as both manufacturing materials and immobilization surfaces. Polymers can also allow the construction of scaffold materials and 3D structures that further elevate the sensing capabilities of traditional 2D biosensors. This review discusses the latest developments in nano-scaled materials and synthesis techniques for polymer structures and their integration into sensing applications by highlighting their various structural advantages in producing highly sensitive tools that rival bench-top instruments. The developments in material design open a new door for decentralized medicine and public protection that allows effective onsite and point-of-care diagnostics.

Wide-Linear Range Cholesterol Detection Using Fe2O3 Nanoparticles Decorated ZnO Nanorods Based Electrolyte-Gated Transistor

Electrolyte-gated transistor (EGT)-based biosensors are created with nanomaterials to harness the advantages of miniaturization and excellent sensing performance. A cholesterol EGT biosensor based on iron oxide (Fe2O3) nanoparticles decorated ZnO nanorods is proposed here. ZnO nanorods are directly grown on the seeded channel using a hydrothermal method, keeping in mind the stability of nanorods on the channel during biosensor measurements in an electrolyte. Most importantly, ZnO nanorods can be effectively grown and modified with Fe2O3 nanoparticles to enhance stability, surface roughness, and performance. The cholesterol oxidase (ChOx) enzyme is immobilized over Fe2O3 nanoparticles decorated ZnO nanorods for cholesterol detection. With cholesterol addition in buffer solution, the electro-oxidation of cholesterol on enzyme immobilized surface led to increased the biosensor’s current response. The cholesterol EGT biosensor detected cholesterol in wide-linear range (i.e., 0.1 to 60.0 mM) with high sensitivity (37.34 μA mM−1cm−2) compared to conventional electrochemical sensors. Furthermore, we obtained excellent selectivity, fabrication reproducibility, long-term storage stability, and practical applicability in real serum samples. The demonstrated EGT biosensor can be extended with changing enzymes or nanomaterials or hybrid nanomaterials for specific analyte detection.

Ultrasensitive electrochemical biosensors for dopamine and cholesterol: recent advances, challenges and strategies

The rapid and accurate determination of the dopamine (neurotransmitter) and cholesterol level in bio-fluids is significant because they are crucial bioanalytes for several lethal diseases, which require early diagnosis. The level of DA in the brain is modulated by the dopamine active transporter (DAT), and is influenced by cholesterol levels in the lipid membrane environment. Accordingly, electrochemical biosensors offer rapid and accurate detection and exhibit unique features such as low detection limits even with reduced volumes of analyte, affordability, simple handling, portability and versatility, making them appropriate to deal with augmented challenges in current clinical and point-of-care diagnostics for the determination of dopamine (DA) and cholesterol. This feature article focuses on the development of ultrasensitive electrochemical biosensors for the detection of cholesterol and DA for real-time and onsite applications that can detect targeted analytes with reduced volumes and sub-picomolar concentrations with quick response times. Furthermore, the development of ultrasensitive biosensors via cost-effective, simple fabrication procedures, displaying high sensitivity, selectivity, reliability and good stability is significant in the impending era of electrochemical biosensing. Herein, we emphasize on recent advanced nanomaterials used for the ultrasensitive detection of DA and cholesterol and discuss in depth their electrochemical activities towards ultrasensitive responses. Key points describing future perspectives and the challenges during detection with their probable solutions are discussed, and the current market is also surveyed. Further, a comprehensive review of the literature indicates that there is room for improvement in the miniaturization of cholesterol and dopamine biosensors for lab-on-chip devices and overcoming the current technical limitations to facilitate full utilization by patients at home.

Non-enzymatic electrochemical cholesterol sensor based on strong host-guest interactions with a polymer of intrinsic microporosity (PIM) with DFT study

Advances in materials science have accelerated the development of diagnostic tools with the last decade witnessing the development of enzyme-free sensors, owing to the improved stability, low cost and simple fabrication of component materials. However, the specificity of non-enzymatic sensors for certain analytes still represents a challenging task, for example the determination of cholesterol level in blood is vital due to its medical relevance. In this work, a reagent displacement assay for cholesterol sensing in serum samples was developed. It is based on coating of a glassy carbon electrode with a polymer of intrinsic microporosity (PIM) that forms a host-guest complex with methylene blue (MB). In the presence of cholesterol, the MB electroactive probe was displaced due to the stronger association of cholesterol guest to the PIM host. The decrease in the oxidative current was proportional to the cholesterol concentration achieving a detection limit of approximately 0.1 nM. Moreover, to further assist the experimental studies, comprehensive theoretical calculations are also performed by using density functional theory (DFT) calculations.

E-Tongues/Noses Based on Conducting Polymers and Composite Materials: Expanding the Possibilities in Complex Analytical Sensing

Conducting polymers (CPs) are extensively studied due to their high versatility and electrical properties, as well as their high environmental stability. Based on the above, their applications as electronic devices are promoted and constitute an interesting matter of research. This review summarizes their application in common electronic devices and their implementation in electronic tongues and noses systems (E-tongues and E-noses, respectively). The monitoring of diverse factors with these devices by multivariate calibration methods for different applications is also included. Lastly, a critical discussion about the enclosed analytical potential of several conducting polymer-based devices in electronic systems reported in literature will be offered.

Recent Development in Nanomaterial-Based Electrochemical Sensors for Cholesterol Detection

Functional nanomaterials have attracted significant attention in a variety of research fields (in particular, in the healthcare system) because of the easily controllable morphology, their high chemical and environmental stability, biocompatibility, and unique optoelectronic and sensing properties. The sensing properties of nanomaterials can be used to detect biomolecules such as cholesterol. Over the past few decades, remarkable progress has been made in the production of cholesterol biosensors that contain nanomaterials as the key component. In this article, various nanomaterials for the electrochemical sensing of cholesterol were reviewed. Cholesterol biosensors are recognized tools in the clinical diagnosis of cardiovascular diseases (CVDs). The function of nanomaterials in cholesterol biosensors were thoroughly discussed. In this study, different pathways for the sensing of cholesterol with functional nanomaterials were investigated.

Gold-Platinum Core-Shell Nanoparticles with Thiolated Polyaniline and Multi-Walled Carbon Nanotubes for the Simultaneous Voltammetric Determination of Six Drug Molecules

In this proof-of-concept study, a novel nanocomposite of the thiolated polyaniline (tPANI), multi-walled carbon nanotubes (MWCNTs) and gold–platinum core-shell nanoparticles (Au@Pt) (tPANI-Au@Pt-MWCNT) was synthesized and utilized to modify a glassy carbon electrode (GCE) for simultaneous voltammetric determination of six over-the-counter (OTC) drug molecules: ascorbic acid (AA), levodopa (LD), acetaminophen (AC), diclofenac (DI), acetylsalicylic acid (AS) and caffeine (CA). The nanocomposite (tPANI-Au@Pt-MWCNT) was characterized with transmission electron microscopy (TEM), Fourier-transform infrared spectroscopy (FT-IR), and X-ray photoelectron spectroscopy (XPS). Using the sensor (GCE-tPANI-Au@Pt-MWCNT) in connection with differential pulse voltammetry (DPV), the calibration plots were determined to be linear up to 570.0, 60.0, 60.0, 115.0, 375.0 and 520.0 µM with limit of detection (LOD) of 1.5, 0.25, 0.15, 0.2, 2.0, and 5.0 µM for AA, LD, AC, DI, AS and CA, respectively. The nanocomposite-modified sensor was successfully used for the determination of these redox-active compounds in commercially available OTC products such as energy drinks, cream and tablets with good recovery yields ranging from 95.48 ± 0.53 to 104.1 ± 1.63%. We envisage that the electrochemical sensor provides a promising platform for future applications towards the detection of redox-active drug molecules in pharmaceutical quality control studies and forensic investigations.

Recent Advances of Conducting Polymers and Their Composites for Electrochemical Biosensing Applications

Conducting polymers (CPs) have been at the center of research owing to their metal-like electrochemical properties and polymer-like dispersion nature. CPs and their composites serve as ideal functional materials for diversified biomedical applications like drug delivery, tissue engineering, and diagnostics. There have also been numerous biosensing platforms based on polyaniline (PANI), polypyrrole (PPY), polythiophene (PTP), and their composites. Based on their unique properties and extensive use in biosensing matrices, updated information on novel CPs and their role is appealing. This review focuses on the properties and performance of biosensing matrices based on CPs reported in the last three years. The salient features of CPs like PANI, PPY, PTP, and their composites with nanoparticles, carbon materials, etc. are outlined along with respective examples. A description of mediator conjugated biosensor designs and enzymeless CPs based glucose sensing has also been included. The future research trends with required improvements to improve the analytical performance of CP-biosensing devices have also been addressed.

β-Cyclodextrin/Fe3O4 nanocomposites for an electrochemical non-enzymatic cholesterol sensor

A sensitive, specific, and miniaturized non-enzymatic cholesterol sensor was prepared based on the competition of inclusion complex formation between β-cyclodextrin (BCD) and cholesterol, and between BCD and methylene blue (MB). BCD was immobilized on the surface of Fe3O4 magnetic nanoparticles instead of the electrode surface to increase the kinetic rate and enhance the sensitivity of the sensor. Furthermore, the use of magnetic nanocomposites and a screen-printed carbon electrode reduces the overall analysis time and simplifies the sample measurement procedures, making the sensor suitable for point-of-care analysis. The electrochemical measurement results of MB, released from the reactions between BCD and solutions containing various concentrations of cholesterol were used as the input signal to calculate the cholesterol concentrations. A good linearity as well as an excellent accuracy and repeatability in the concentration range of 0-150 μM with an estimated limit of detection of 2.88 μM could be achieved by using the amperometric technique at a constant potential of -0.43 V. The sensor showed a good selectivity in the presence of 1 mM concentrations of interfering agents, including NaCl, CaCl2, glycine, glucose, and ascorbic acid. Furthermore, a validation performed for cholesterol determination in milk samples was in agreement with the measurements performed by using the HPLC method, suggesting that the developed sensor is reliable.

Developments and applications of nanomaterial-based carbon paste electrodes

This review summarizes the progress that has been made in the past ten years in the field of electrochemical sensing using nanomaterial-based carbon paste electrodes. Following an introduction into the field, a first large section covers sensors for biological species and pharmaceutical compounds (with subsections on sensors for antioxidants, catecholamines and amino acids). The next section covers sensors for environmental pollutants (with subsections on sensors for pesticides and heavy metal ions). Several tables are presented that give an overview on the wealth of methods (differential pulse voltammetry, square wave voltammetry, amperometry, etc.) and different nanomaterials available. A concluding section summarizes the status, addresses future challenges, and gives an outlook on potential trends.

Prussian blue-doped nanosized polyaniline for electrochemical detection of benzenediol isomers

Simultaneous speciation of benzenediol isomers (BDIs), 1,2-benzenediol (catechol, CC), 1,3-benzenediol (resorcinol, RS), and 1,4-benzenediol (hydroquinone, HQ), was investigated by differential pulse voltammetry (DPV) using a graphite paste electrode (GPE) modified with Prussian blue-polyaniline nanocomposite. The modified GPE showed good stability, sensitivity, and selectivity properties for all the three BDIs. Prussian blue-doped nanosized polyaniline (PBNS-PANI) was synthesized first by using mechanochemical reactions between aniline and ferric chloride hexahydrate as the oxidants and then followed by the addition of potassium hexacyanoferrate(II) in a solid-state and template-free technique. The material was characterized by scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy (FT-IR), and X-ray photoelectron spectroscopy (XPS). The DPV measurements are performed in phosphate electrolyte solution with pH 4.0 at a potential range of - 0.1 to 1.0 V. The proposed modified electrode displayed a strong, stable, and continuous three well-separated oxidation peaks towards electrooxidation at potentials 0.20, 0.31, and 0.76 V for HQ, CC, and RS, respectively. The calibration curves were linear from 1 to 350.5 μM for both HQ and CC, while for RS, it was from 2 to 350.5 μM. The limit of detection was determined to be 0.18, 0.01, and 0.02 μM for HQ, CC, and RS, respectively. The analytical performance of the PBNS-PANI/GPE has been evaluated for simultaneous determination of HQ, CC, and RS in creek water, commercial hair dye, and skin whitening cream samples with satisfactory recoveries between 90 and 106%. Overall, we demonstrated that the presence of NS-PANI and PB resulted in a large redox-active surface area that enabled a promising analytical platform for simultaneous detection of BDIs. Graphical abstract.

Progress in Conductive Polyaniline-Based Nanocomposites for Biomedical Applications: A Review

Inherently conducting polymers (ICPs) are a specific category of synthetic polymers with distinctive electro-optic properties, which involve conjugated chains with alternating single and double bonds. Polyaniline (PANI), as one of the most well-known ICPs, has outstanding potential applications in biomedicine because of its high electrical conductivity and biocompatibility caused by its hydrophilic nature, low-toxicity, good environmental stability, and nanostructured morphology. Some of the limitations in the use of PANI, such as its low processability and degradability, can be overcome by the preparation of its blends and nanocomposites with various (bio)polymers and nanomaterials, respectively. This review describes the state-of-the-art of biological activities and applications of conductive PANI-based nanocomposites in the biomedical fields, such as antimicrobial therapy, drug delivery, biosensors, nerve regeneration, and tissue engineering. The latest progresses in the biomedical applications of PANI-based nanocomposites are reviewed to provide a background for future research.

Effects of Cholesterol Extraction Process and Fat and Whey Protein Additions on Ice Cream Mixes

The aim of this work was to evaluate the cholesterol extraction process in ice cream mixes (ICMs) by using β-cyclodextrin (βCD) and to analyze the effect of this extraction on the ICM rheological, stability, and sensory characteristics. The effects of fat and whey protein (WP) additions on ICM stability were also evaluated. The maximum percentage obtained for cholesterol extraction was 93.6%. The flow curves indicated that ICM showed a thixotropic behavior before and after cholesterol extraction, which was enhanced when the fat content and/or percentage of βCD increased. The stability of ICM with cholesterol-reduced content (RCho-ICM) was influenced by the fat content and/or the presence of WP. The RCho-ICM with the highest fat and/or WP addition showed less tendency to melt and had the smallest amount of accumulated molten liquid. These latter ICMs presented the slowest melting rates. Also, RCho-ICMs proved to be more stable than ICMs. RCho-ICM samples obtained with a ratio of βCD/fat content of 1% w/w were evaluated by a trained sensory panel. In addition, an acceptability test of the sample with better sensory attributes was conducted. PRACTICAL APPLICATION: The effects of a cholesterol extraction process and fat and whey protein additions on the rheological and stability characteristics of ice cream mixes were evaluated. The extraction of cholesterol from an ice cream mix is interesting from a nutritional point of view and the extraction process of cholesterol itself may also help to improve the mix stability by controlling the fat and/or whey protein contents. These findings may prove useful as a starting point for the rational design of new functional ice cream mixes.

PVIM–Co5POM/MNC composite as a flexible electrode for the ultrasensitive and highly selective non-enzymatic electrochemical detection of cholesterol

A novel electrochemical sensor was developed based on poly(ionic liquid) [PVIM]–cobalt polyoxometalate (Co₅POM) supported on carbonaceous materials for the highly selective and ultrasensitive non-enzymatic detection of cholesterol.

Bifunctional magnetic nanoparticles for efficient cholesterol detection and elimination via host-guest chemistry in real samples

Cholesterol is an essential compound for maintaining cellular homeostasis and human healthy. Sensitive detection of cholesterol and efficient elimination of excess cholesterol have become the essential manipulations in clinical diagnosis and health management. To date, it is still quite challenging that cholesterol detection and elimination tasks are carried out simultaneously. In this study, bifunctional magnetic nanoparticles (Fe₃O₄@PDA-PBA-CD) are designed and fabricated to overcome this difficulty. Taking advantages of competitive host-guest interaction and magnetic separation, highly efficient, reusable and simultaneous cholesterol detection and elimination can be achieved. The limit of detection is determined to be 4.3 nM, which is comparable or even lower than existing methods. The distinguished performance may attribute to the high loading efficiency and magnetic enrichment of nanoparticles. Besides, this efficient strategy is resistant to interfering substances, thus realizing sensitive cholesterol detection in real sample. Simultaneously, the bifunctional magnetic nanoparticles also have up to 95% cholesterol elimination efficiency, which is higher than previous reported methods. Furthermore, the nanoparticles are turned out to be reusable within 5 times without noticeable loss in cholesterol elimination efficiency. Therefore, the bifunctional magnetic nanoparticles fabricated here could hold great potential for simultaneous cholesterol detection and elimination in practical applications.