Colorimetric based sensing of dopamine using ionic liquid functionalized drug mediated silver nanostructures

Nanozyme-based sensing of dopamine using cobalt-doped hydroxyapatite nanocomposite from waste bones

Dopamine is one of the most important neurotransmitters and plays a crucial role in various neurological, renal, and cardiovascular systems. However, the abnormal levels of dopamine mainly point to Parkinson's, Alzheimer's, cardiovascular diseases, etc. Hydroxyapatite (HAp), owing to its catalytic nature, nanoporous structure, easy synthesis, and biocompatibility, is a promising matrix material. These characteristics make HAp a material of choice for doping metals such as cobalt. The synthesized cobalt-doped hydroxyapatite (Co-HAp) was used as a colorimetric sensing platform for dopamine. The successful synthesis of the platform was confirmed by characterization with FTIR, SEM, EDX, XRD, TGA, etc. The platform demonstrated intrinsic peroxidase-like activity in the presence of H2O2, resulting in the oxidation of 3,3',5,5'-tetramethylbenzidine (TMB). The proposed sensor detected dopamine in a linear range of 0.9-35 μM, a limit of detection of 0.51 µM, limit of quantification of 1.7 µM, and an R2 of 0.993. The optimization of the proposed sensor was done with different parameters, such as the amount of mimic enzyme, H2O2, pH, TMB concentration, and time. The proposed sensor showed the best response at 5 mg of the mimic enzyme, pH 5, 12 mM TMB, and 8 mM H2O2, with a short response time of only 2 min. The fabricated platform was successfully applied to detect dopamine in physiological solutions.

Uric acid quantification via colorimetric detection utilizing silver oxide-modified activated carbon nanoparticles functionalized with ionic liquid

Uric acid (UA) is a significant indicator of human health because it is linked to several diseases, including renal failure, kidney stones, arthritis, and gout. Uric acid buildup in the joints is the source of chronic and painful diseases. When UA is present in large quantities, it causes tissue injury in the joints that are afflicted. In this research, silver oxide-doped activated carbon nanoparticles were synthesized and then functionalized with an ionic liquid. The synthesized nanomaterial assembly was employed as a colorimetric sensing platform for uric acid. Activated carbon offers a large internal surface area that acts as a good carrier for catalytic reactions. A salt-melting approach was used to synthesize the silver oxide-doped activated carbon nanocomposite. The synthesis was confirmed through various techniques, such as UV-vis spectrophotometer, FTIR, XRD, SEM, and EDX. The colorimetric change from blue-green to colorless was observed with the naked eye and confirmed by UV-vis spectroscopy. To obtain the best colorimetric change, several parameters, such as pH, capped NP loading, TMB concentration, hydrogen peroxide concentration, and time, were optimized. The optimized experimental conditions for the proposed sensor were pH 4 with 35 μL of NPs, a 40 mM TMB concentration, and a 4 minutes incubation time. The sensor linear range is 0.001-0.36 μM, with an R2 value of 0.999. The suggested sensor limits of detection and quantification are 0.207 and 0.69 nM, respectively. Potential interferers, such as ethanol, methanol, urea, Ca2+, K+, and dopamine, did not affect the detection of uric acid.

Paracetamol-Mediated Synthesis of Silver Nanoparticles and Their Functionalization with Ionic Liquid for the Colorimetric Biosensing of Ascorbic Acid

Ascorbic acid is a vital biomolecule for human beings. When the body's level of ascorbic acid is abnormal, it can lead to a number of illnesses. Its appropriate concentration is necessary for the oxidation of prostaglandins and cyclic adenosine monophosphate, the production of dopamine, norepinephrine, epinephrine, and carnitine, and the expansion and durability of the collagen triple helix in humans. In the present work, silver nanoparticle synthesis was performed through a paracetamol-mediated approach. Different characterization techniques, such as X-ray diffractometry (XRD), energy dispersive X-ray (EDX), Fourier transform infrared (FTIR), and scanning electron microscopy (SEM), were used to confirm the prepared nanoparticles. Subsequently, the prepared Ag NPs functionalized with an ionic liquid were used as a sensing platform for ascorbic acid in blood serum samples. To achieve the best possible results, the proposed biosensor was optimized with different parameters such as TMB concentration, time, amount of capped nanoparticles (NPs), and pH. The proposed biosensor offers a sensitive and straightforward method for ascorbic acid with a linear range from 2 × 10-9 to 3.22 × 10-7 M, an LOD of 1.3 × 10-8 M, an LOQ of 4.3 × 10-8 M, and an R2 of 0.9996, Moreover, applications of the proposed biosensor were successfully used for the detection of ascorbic acid in samples of human plasma, suggesting that Ag NPs with high peroxidase-like activity, high stability, and facile synthesis exhibited promising applications in biomedical fields.

Co-Doped CeO2/Activated C Nanocomposite Functionalized with Ionic Liquid for Colorimetric Biosensing of H2O2 via Peroxidase Mimicking

Hydrogen peroxide acts as a byproduct of oxidative metabolism, and oxidative stress caused by its excess amount, causes different types of cancer. Thus, fast and cost-friendly analytical methods need to be developed for H₂O₂. Ionic liquid (IL)-coated cobalt (Co)-doped cerium oxide (CeO₂)/activated carbon (C) nanocomposite has been used to assess the peroxidase-like activity for the colorimetric detection of H₂O₂. Both activated C and IL have a synergistic effect on the electrical conductivity of the nanocomposites to catalyze the oxidation of 3,3',5,5'-tetramethylbenzidine (TMB). The Co-doped CeO₂/activated C nanocomposite has been synthesized by the co-precipitation method and characterized by UV-Vis spectrophotometry, FTIR, SEM, EDX, Raman spectroscopy, and XRD. The prepared nanocomposite was functionalized with IL to avoid agglomeration. H₂O₂ concentration, incubation time, pH, TMB concentration, and quantity of the capped nanocomposite were tuned. The proposed sensing probe gave a limit of detection of 1.3 × 10^-8 M, a limit of quantification of 1.4 × 10^-8 M, and an R² of 0.999. The sensor gave a colorimetric response within 2 min at pH 6 at room temperature. The co-existing species did not show any interference during the sensing probe. The proposed sensor showed high sensitivity and selectivity and was used to detect H₂O₂ in cancer patients' urine samples.

Recent advances in nanomaterials-based optical sensors for detection of various biomarkers (inorganic species, organic and biomolecules)

This review briefly emphasizes the different detection approaches (electrochemical sensors, chemiluminescence, surface-enhanced Raman scattering), functional nanostructure materials (quantum dots, metal nanoparticles, metal nanoclusters, magnetic nanomaterials, metal oxide nanoparticles, polymer-based nanomaterials, and carbonaceous nanomaterials) and detection mechanisms. Further, this review emphasis on the integration of functional nanomaterials with optical spectroscopic techniques for the identification of various biomarkers (nucleic acids, glucose, uric acid, oxytocin, dopamine, ascorbic acid, bilirubin, spermine, serotonin, thiocyanate, Pb²⁺ , Cu²⁺ , Hg²⁺ , F^- , peptides, and cancer biomarkers (mucin 1, prostate specific antigen, carcinoembryonic antigen, CA15-3, human epidermal growth factor receptor 2, C-reactive protein, and interleukin-6). Analytical characteristics of nanomaterials-based optical sensors are summarized in Tables, providing the insights of nanomaterials-based optical sensors for biomarkers detection. Finally, the opportunities and challenges of nanomaterials-based optical analytical approaches for the detection of various biomarkers (inorganic, organic, biomolecules, peptides and proteins) are discussed.

Development of a Nonenzymatic Colorimetric Sensor for the Detection of Uric Acid Based on Ionic Liquid-Mediated Nickel Nanostructures

Uric acid (UA) is a metabolic byproduct of purine nucleotides and is excreted as a urine component. Abnormalities in UA metabolism cause localized inflammation due to crystal deposition and can lead to various diseases. In the current study, we successfully fabricated a biosensor based on 1-H-3-methylimidazolium acetate (ionic liquid, IL)-capped nickel nanoparticles (NiNPs) for the detection of uric acid in test samples. The structures of IL-capped NiNPs and their precursors were characterized by Fourier transform infrared spectroscopy, scanning electron microscopy, and X-ray diffraction. The IL-capped NiNPs possessed intrinsic peroxidase-like properties and displayed selective UA quenching after interacting with 3,3',5,5'-tetramethylbenzidine (TMB) solution. Different parameters such as pH, time, IL, TMB, and UA concentration were optimized to obtain the best results for the proposed sensor. The UA biosensor shows good responses in the linear range from 1 × 10^-8 to 2.40 × 10^-6 M, with a lower limit of detection of 1.30 × 10^-7 M, a limit of quantification of 4.3 × 10^-7 M, and an R ² value of 0.9994. For the colorimetric detection of UA, the proposed sensor gave a short time response of 4 min at room temperature and pH 7.5. The proposed sensing probe detects UA in real serum samples and could be used as a selective sensor for UA in the real sample detection.

SiO2/Al2O3/C grafted 3-n propylpyridinium silsesquioxane chloride-based non-enzymatic electrochemical sensor for determination of carcinogenic nitrite in food products

The excessive uptake of nitrite is perilous and detrimental for human health that prone to cancer disease. Herein, described the synthesis of SiO₂/Al₂O₃/C material through the sol-gel procedure followed by grafting with 3-n propylpyridinium silsesquioxane chloride organic ligand for enhancing electrochemical activity. H-NMR, ¹³C NMR, and ²⁹Si studies were performed for confirmation of surface functionalization through the grafting technique. The surface morphology was evaluated through SEM and TEM techniques. The material showed an irregular and flakes-like structure that exhibited more compactness and conglomerate structure with no segregation in phase was observed after grafting. The elemental composition was confirmed from EDX analysis. The electrochemical measurements were performed with cyclic voltammetry, electrochemical impedance spectroscopy (EIS), and chronoamperometry. The prepared hybrid inorganic-organic composite Si/C/Al/SiPy⁺Cl^- was applied for the modification of the glassy carbon (GC) electrode and assessed as a sensor for nitrite determination. The sensor showed the low limit of detection (0.01 μM), low limit of quantification (0.08 μM), wide linear response range (0.2-280 μM), and high sensitivity (410 μA·μM^-1). It gave a quick response time of <1 s in the presence of 70 μM nitrite. The fabricated sensor showed high sensitivity, chemical stability, and insignificant interference from co-existing species present in sausage meat and food industry discharges. The repeatability of the sensor was evaluated as 2.5 % R.S.D.; for n = 10 at 50 μM nitrite.

Highly Stable Copper Nano Cluster on Nitrogen-Doped Graphene Quantum Dots for the Simultaneous Electrochemical Sensing of Dopamine, Serotonin, and Nicotine; a Possible Addiction Scrutinizing Strategy

A highly stable copper nanocluster CuNC@N-GQD which exhibited stability for more than one year was synthesized using nitrogen doped graphene quantum dots (N-GQDs) as reducing and capping agents and smaller...

Ionic-Liquid-Stabilized TiO2 Nanostructures: A Platform for Detection of Hydrogen Peroxide

Hydrogen peroxide (H2O2) acts as a signaling molecule to direct different biological processes. However, its excess amount results in oxidative stress, which causes the onset of different types of cancers. TiO2 nanostructure was synthesized by a facile hydrothermal method. The prepared material was characterized by FTIR spectroscopy, XRD, SEM, EDX, TGA, and Raman spectroscopy, which confirmed the formation of nanostructured material. Subsequently, the prepared nanoparticles (NPs) were capped with 1-H-3-methylimidazolium acetate ionic liquid (IL) to achieve its deagglomeration and functionalization. A new colorimetric sensing probe was prepared for the detection of H2O2 based on ionic liquid-capped TiO2 nanoparticles (TiO2/IL) and 3,3',5,5'-tetramethylbenzidine (TMB) dye, which acts as an oxidative chromogenic substrate. H2O2 reacts with TMB, in the presence of ionic liquid-coated TiO2 NPs, to form a blue-green product. The color was visualized with the naked eye, and the colorimetric change was confirmed by a UV-vis spectrophotometer. To obtain the best response of the synthesized sensor, different parameters (time, pH, concentrations, loading of nanomaterials) were optimized. It showed a low limit of detection 8.61 × 10-8 M, a high sensitivity of 2.86 × 10-7 M, and a wide linear range of 1 × 10-9-3.6 × 10-7 M, with a regression coefficient (R 2) value of 0.999. The proposed sensor showed a short incubation time of 4 min. The sensing probe did not show any interference from the coexisting species. The TiO2/IL sensor was effectively used for finding H2O2 in the urine samples of cancer patients.

Nanoparticle-based colorimetric sensors to detect neurodegenerative disease biomarkers

Neurodegenerative disorders (NDDs) are progressive, incurable health conditions that primarily affect brain cells, and result in loss of brain mass and impaired function. Current sensing technologies for NDD detection are limited by high cost, long sample preparation, and/or require skilled personnel. To overcome these limitations, optical sensors, specifically colorimetric sensors, have garnered increasing attention towards the development of a cost-effective, simple, and rapid alternative approach. In this review, we evaluate colorimetric sensing strategies of NDD biomarkers (e.g. proteins, neurotransmitters, bio-thiols, and sulfide), address the limitations and challenges of optical sensor technologies, and provide our outlook on the future of this field.

Influence of laser and alkali treatment on an Ag/TiO2nanotube based dopamine sensor

Herein, TiO₂nanotubes (T-NTs) arrays were subjected to two types of treatment followed by a simple metal deposition technique to significantly enhance the performances of T-NTs based electrochemical sensing of dopamine. The first type of treatment was done by soaking T-NTs in sodium hydroxide solution for an optimal time to enhance the conductivity and charge carrier density. The second type of treatment employed was laser irradiation, which induces crystallinity disorder and forms rutile TiO₂, promoting active analyte adsorption sites. Afterward, silver (Ag) was electro-deposited on the T-NTs as a dopamine sensing catalyst to form T-NTs/Ag nanohybrids. The dual-treated T-NTs based sensor showed 3-fold enhancement in sensitivity (from 8.2μA mM^-1cm^-2to 32μA mM^-1cm^-2), reduced charge transfer resistance (from 38 × 10^-6Ω to 0.7 × 10^-6Ω), above 2 order higher donor charge density (from 3.58 × 10¹⁸cm^-3to 1.41 × 10²¹cm^-3), and reduced limit of detection (from 32.3μM to 2.8μM) in comparison to plain T-NTs based sensor. In addition, the sensitivity reported here is significantly higher than most of the previously reported TiO₂based dopamine sensors. Perspective-wise, the dual treatment approach is a promising technique and is highly desirable for enhancing the performances of T-NTs and other nanomaterial based electrochemical sensors.

The biocompatible validity of amino acid ionic liquid mediated gold nanoparticles for enhanced activity and structural stability of papain

During the past few decades, gold nanoparticles (AuNPs) have attracted a lot of attention owing to their biomedical applications, like therapeutics and drug delivery; however, the detailed biomolecular interactions and structural alteration of naturally occurring biomolecules, such as enzymes, in AuNPs remain unknown. The effects of various additives on the thermal and structural properties, and activity of proteins/enzymes have been scavenged and communicated intensively in the literature; however, the synthesis of ionic liquid (IL) mediated AuNPs solely for the purpose of enzyme activity boosting and stability modulation has not yet been reported. In the current study, we explore the role of cholinium tryptophan [CHO][Trp] and tetraethyl tryptophan [TEA][Trp]IL-mediated gold nanoparticles (AuNPs) on the activity enhancement and structural stability of papain. Our results showed that [CHO][Trp] and [TEA][Trp]IL-mediated AuNPs efficiently increased the proteolytic activity of papain, which was increased from 100 to 206% for [CHO][Trp]IL-mediated AuNPs and enhanced from 100 to 136% in [TEA][Trp]IL-mediated AuNPs. Additionally, extended differential scanning calorimetry (DSC) results showed that these AAIL-mediated AuNPs maintained the thermal stability of papain only at lower concentration. Spectroscopic studies conclude that the tryptophan (Trp) group of papain is expanded more towards the polar environment in the presence of [CHO][Trp] as compared to [CHO][Trp]IL mediated AuNPs. The far CD spectral and deconvoluted results show that the α-helical and β-turn contents of the secondary structure of papain are preserved to a large extent; however, disruption in the β-sheet has been observed for both AAIL-mediated AuNPs. Dynamic light scattering (DLS), zeta potential and transmission electron microscopy (TEM) results illustrate the distinct interactive behavior of papain for both types of AAIL-mediated AuNPs. The immobilization of papain is higher on [CHO][Trp]AuNPs compared to [TEA][Trp]AuNPs and papain surrounds [CHO][Trp]AuNPs on all sides, which is lacking in [TEA][Trp]AuNPs.