Ractopamine as a novel reagent for the fabrication of gold nanoparticles: Colorimetric sensing of cysteine and Hg2+ ion with different spectral characteristics

Green synthesized AgNPs as a probe for colorimetric detection of Hg (II) ions in aqueous medium and fluorescent imaging in liver cell lines and its antibacterial activity

The present research aimed at green synthesis of Ag nanoparticles (AgNPs) based colorimetric sensor using persimmon leaf extract (PLE) for selective detection of mercuric ion (Hg2+). Optimization of reaction conditions viz. pH, concentration of PLE, time was done and further AgNPs were characterized using UV, IR, FE-SEM, EDX, XRD and TEM analysis. The developed AgNPs were evaluated for the selective colorimetric detection of Hg2+ in aqueous medium and fluorescence imaging of Hg2+ ions in liver cell lines. Later, the antibacterial activity of AgNPs was performed against S. aureus and E. coli. The findings of the study revealed that PLE mediated AgNPs exhibited notable limit of detection up to 0.1 ppb, high efficiency, and stability. The antibacterial study indicated that developed AgNPs has impressive bacterial inhibiting properties against the tested bacterial strains. In conclusion, developed biogenic AgNPs has high selectivity and notable sensitivity towards Hg2+ ions and may be used as key tool water remediation.

Picomolar level sensorial dual colorimetric gold nanoparticle sensor for Zn2+ and Hg2+ ions synthesized from bark extract of Lannea Grandis Coromandelica and its wide range applications in real sample analysis

In this work a facile, rapid, reproducible and non-toxic approach has been demonstrated for synthesis of most stable AuNPs from bark extract of Lannea Grandis Coromandelica. UV-Visible spectroscopy, FTIR, TEM, SAED, EDX, XRD, DLS, Zeta Potential, FE-SEM, AFM and XPS techniques were employed for the characterization of synthesized LGC-AuNPs. The UV-Vis spectra of LGC-AuNPs gave SPR peak at 536 nm while the TEM analysis revealed LGC-AuNPs have 20.75 nm size with spherical in shape. DLS study showed the AuNPs have average diameter 50.18 nm. The synthesized AuNPs exhibited very high selectivity, rapid response in recognition towards Zn2+ and Hg2+ ions by changing its color within 20 sec. This proposed sensor can detect very low picomolar level of Zn2+ and Hg2+ ions (LOD value for Zn2+ and Hg2+ were found 1.36 pM and 24.60 pM respectively). Here we also studied effect of several factors such as variation of conc of gold, temperature, incubation time, pH, salt, solvent (polar protic and polar aprotic) to know in which condition AuNPs have high stability and sensitivity. The data revealed that synthesized AuNPs was stable up to two years at pH 6.5 at room temperature in water media and under this condition, it shows maximum sensitivity and reactivity. Moreover, here interference study was carried out to identify high selectivity of synthesized LGC-AuNPs probe in presence of different metal ions. The real sample analyses also revealed the great applicability of this probe. Therefore, this simple, rapid, low-cost, sensing activity appeared to hold great sensibleness for detection of heavy metal ions in real sample.

Synthesis of multicolor silver nanostructures for colorimetric sensing of metal ions (Cr3+, Hg2+ and K+) in industrial water and urine samples with different spectral characteristics

In this work, we have synthesized four different color (yellow, orange, green, and blue (multicolor)) silver nanostructures (AgNSs) by chemical reduction method where silver nitrate, sodium borohydride and hydrogen peroxide were used as reagents. The as-synthesized multicolor AgNSs were successfully functionalized with bovine serum albumin (BSA) and applied as a colorimetric sensor for the assaying of metal cations (Cr³⁺, Hg²⁺, and K⁺). The addition of metal ions (Cr³⁺, Hg²⁺, and K⁺) into BSA functionalized AgNSs (BSA-AgNSs) causes the aggregation of BSA-AgNSs, and are accompanied by visual color changes with red or blue shift in the surface plasmon resonance (SPR) band of BSA-AgNSs. The BSA-AgNSs show different SPR characteristic for each metal ions (Cr³⁺, Hg²⁺, and K⁺) with exhibiting different spectral shift and color change. The yellow color BSA-AgNSs (Y-BSA-AgNSs) act as a probe for sensing Cr³⁺, orange color BSA-AgNSs (O-BSA-AgNSs) act as probe for Hg²⁺ ion assay, green color BSA-AgNSs (G-BSA-AgNSs) act as a probe for the assaying of both K⁺ and Hg²⁺, and blue color BSA-AgNSs (B-BSA-AgNSs) act as a sensor for colorimetric detection of K⁺ ion. The detection limits were found to be 0.26 μM for Cr³⁺ (Y-BSA-AgNSs), 0.14 μM for Hg²⁺ (O-BSA-AgNSs), 0.05 μM for K⁺ (G-BSA-AgNSs), 0.17 μM for Hg²⁺ (G-BSA-AgNSs), and 0.08 μM for K⁺ (B-BSA-AgNSs), respectively. Furthermore, multicolor BSA-AgNSs were also applied for assaying of Cr³⁺, and Hg²⁺ in industrial water samples and K⁺ in urine sample.

Specifically functionalized MTT-Ag NP/SA film sensor for the ultrasensitive detection of Hg2+ in lettuce samples

In the present study, highly efficient 5-Methyl-1,3,4-thiadiazole-2-thiol-modified silver nanoparticles (MTT-Ag NPs) were successfully synthesized and could be used for convenient and sensitive detection of Hg2+. MTT acts as a protective agent by forming Ag-S bonds with Ag NPs, meantime, MTT can also be captured Hg2+ through NN bonds. Furthermore, to improve the sustainability and stability of MTT-Ag NPs, sodium alginate (SA) was used as a substrate material for the formation of SA-MTT-Ag NPs films. As expected, SA-MTT-Ag NPs could be stored for more than 180 days at room temperature. When used SA-MTT-Ag NPs thin films as colourimetric sensors for detection of Hg2+ in lettuce, the low detection limit could be down to 0.22 μM (44 ppb) with wide linear range (0-1 µM and 1-150 µM) and good recovery (96.25 % - 98.75 %). Therefore, the method enables highly selective and efficient monitoring of Hg2+ in food samples.

Conjugation of cysteamine functionalized nanodiamond to gold nanoparticles for pH enhanced colorimetric detection of Cr3+ ions demonstrated by real water sample analysis

A cysteamine functionalized nanodiamond (NDC) was conjugated to gold nanoparticles (AuNPs) to deliver NDC@AuNPs and utilized in enhanced colorimetric detection of Cr³⁺ at pH 6 environment. The conjugation was validated using FTIR, TEM, PXRD, DLS, and zeta potential investigations. At pH 6, superior sensory response of NDC@AuNPs to Cr³⁺ than that of other ions was validated by UV-vis spectroscopy and colorimetric photographs. Results from UV-vis titrations displayed a linear regression from 0.01 to 0.4 µM with a LOD of 0.236 ± 0.005 nM. The particle aggregation, size variations, potential changes, and binding modes are investigated using TEM, DLS, and FTIR techniques to explore the underlying mechanisms. By adding the EDTA, sensory response is reversible up to 4 cycles. Finally, spiked real water experiments show improved sensing of Cr³⁺ at pH 6 via the observed recovery between 96 and 110 %, which is in good agreement with the ICP-mass data.

Progress, evolving therapeutic/diagnostic approaches, and challenges in the management of hepatitis C virus infections

Hepatitis C virus (HCV) infections are emerging as one of the foremost challenges in healthcare owing to its chronicity and the virus’s quasispecies nature. Worldwide, over 170 million people are chronically infected with HCV, with an annual mortality of over 500,000 people across the world. The emerging pathophysiological evidence links HCV infections to a risk of developing liver diseases such as cirrhosis and hepatocellular carcinoma. Despite the great strides that have been made towards understanding the pathophysiology of disease progression, the tailored treatments of HCV infection remain to be established. The present review provides an update of the literature pertaining to evolving therapeutic approaches and prophylactic measures for the effective management of HCV infections. An extensive discussion of established and experimental immune prophylactic measures also sheds light on current developments in the design of vaccination strategies against HCV infection. We have also attempted to address the application of nanotechnology in formulating effective therapeutic interventions against HCV. Pointing out the limitations of the existing diagnostic methods and therapeutic approaches against HCV might inspire the design and development of novel, efficient, reliable, and cost-effective diagnostic technologies as well as novel therapeutic and immune prophylactic interventions for the effective management of HCV.

Innovative and versatile nanoplasmonic approach for the full sensing of proteinogenic aminoacids in nutritional supplements

A current nourishment issue is the development of smart and reliable analytical strategies to control in a simple way main bioactive compounds of nutritional supplements whose increasing use is deemed a trend nowadays. With this aim a quick and highly sensitive plasmonic sensor using simple citrate coated gold nanoparticles (AuNPs) as optical probe, was developed for both qualitative and quantitative global assessment of all the proteinogenic amino acids in nutritional supplements. AuNPs of five different sizes (from 19 to 74 nm) were synthesized, characterized and evaluated as optimal transductor element for the sensing approach. Critical physic-chemical conditions controlling aggregation (pH, incubation time, AuNPs amount and ionic strength) were investigated on the main five types of aas, structurally different attending to their R-side chain and with expected distinctive behaviour on aggregation mechanisms, which are also discussed. All proteinogenic amino acids induced AuNPs aggregation at low pH (2.5) causing a change in the colour solution from red to blue, as well as a redshift in the plasmon band from 518 nm (disperse NPs) to 650 nm (aggregated NPs). Based on this sensing approach two different strategies are allowed, a preliminary qualitative/semi-quantitative screening just by the naked eye (simple spot test) and a second quantitative confirmation procedure using the analytical signal (A₆₅₀/A₅₁₈). Reliability of quantitative approach was assessed by an exhaustive validation procedure, where matrix effects and potential interferences usually present in commercial samples and affecting the analytical signal were mainly focussed. The results for the analysis of complex nutritional samples were validated by means of a statistical comparison with those ones of the official reference Kjeldahl method (paired Student test-t) at a 95% confidence level. This is the first sensing approach able to provide the global estimation of proteinogenic aas amount based on their simply AuNPs aggregation induction, irrespectively of their R-side chain structure.

“Turn on” Fluorescence Sensor of Glutathione Based on Inner Filter Effect of Co-Doped Carbon Dot/Gold Nanoparticle Composites

Glutathione (GSH) is a thiol that plays a significant role in nutrient metabolism, antioxidant defense and the regulation of cellular events. GSH deficiency is related to variety of diseases, so it is useful to develop novel approaches for GSH evaluation and detection. In this study we used nitrogen and phosphorus co-doped carbon dot-gold nanoparticle (NPCD–AuNP) composites to fabricate a simple and selective fluorescence sensor for GSH detection. We employed the reductant potential of the nitrogen and phosphorus co-doped carbon dots (NPCDs) themselves to form AuNPs, and subsequently NPCD–AuNP composites from Au3+. The composites were characterized by using a range of spectroscopic and electron microscopic techniques, including electrophoretic light scattering and X-ray diffraction. The overlap of the fluorescence emission spectrum of NPCDs and the absorption spectrum of AuNPs resulted in an effective inner filter effect (IFE) in the composite material, leading to a quenching of the fluorescence intensity. In the presence of GSH, the fluorescence intensity of the composite was recovered, which increased proportionally to increasing the GSH concentration. In addition, our GSH sensing method showed good selectivity and sensing potential in human serum with a limit of detection of 0.1 µM and acceptable results.

Architecture of a multi-channel and easy-to-make microfluidic paper-based colorimetric device (μPCD) towards selective and sensitive recognition of uric acid by AuNPs: an innovative portable tool for the rapid and low-cost identification of clinically relevant biomolecules

Uric acid (UA) is the end product of purine metabolism. Uric acid is usually excreted in the urine, but its abnormal increase and toxic amount can lead to diseases such as gout, hyperuricemia, Lesch-Nyhan syndrome, and cardiovascular disease. On the other hand, UA reduction can lead to neurodegenerative diseases such as sarcoma, glioblastoma, Hodgkin, and etc. Therefore, rapid identification of UA is of great importance. In this work, a simple, portable, inexpensive, and fast microfluidic paper-based colorimetric sensor based on the color change in the presence of UA by using AuNPs was developed. The results can be easily identified with naked eye and further confirmed by UV-vis spectrophotometry. In this method, iron pattern and fiberglass paper were used to construct diagnostic areas and hydrophilic microfluidic channels. We greatly reduced the preparation time of this pattern using a magnet (about three minutes). In this work, four types of nanoparticles with different lower limit of quantification (LLOQ) were used. Linear range of 10-6 to 10-3 M and LLOQ of 10-6 M were obtained for the determination of uric acid using AuNPs-CysA as optical probe. Also, by AuNPs as optical probe a linear range of 10-4 to 10-2 M and the obtained LLOQ was 10-4 M. Finally, by AuNFs as optical probe linear range from 10-6 to 10-2 M and 5 × 10-5 to 10-2 M along with LLOQ of 10-6 and 5 × 10-5 M, respectively. The designed system successfully studied in human urine samples.

Colorimetric detection of Hg(II) by γ-aminobutyric acid-silver nanoparticles in water and the assessment of antibacterial activities

In this work, we report the synthesis of silver nanoparticles (AgNPs) via a wet-chemical reduction procedure using citrate (Cit) and γ-aminobutyric acid (GABA) as stabilizers. The formation of GABA-Cit@AgNPs was confirmed by UV-vis spectroscopy with a surface plasmon resonance band at 393 nm clearly confirming the formation of silver nanoparticles. AgNPs were characterized using UV-vis spectroscopy, attenuated total reflectance-fourier transform infrared spectroscopy (ATR-FTIR), transmission electron microscope (TEM), energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), dynamic light scattering (DLS), and zeta potential. The as-prepared AgNPs can be used for the detection of hazardous mercury ions (Hg²⁺) in water by colorimetric method with a limit of detection (LOD) and limit of quantitation (LOQ) of 2.37 μM and 3.99 μM, respectively. The linear working range for Hg²⁺ detection is 5-35 μM and the sensor probe was applied to investigate Hg²⁺ in real drinking water samples with satisfied results. Rapid response to Hg²⁺ is also observed when the nanoparticles are composited within hydrogels. Moreover, GABA-Cit@AgNPs shows antibacterial activity against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus). The fast and sensitive response of the proposed Hg²⁺ sensor, together with its antibacterial activities, makes GABA-Cit@AgNPs potentially applicable for the development of cheap, portable, colorimetric sensors in fieldwork.

Dual Colorimetric Sensor for Hg2+/Pb2+ and an Efficient Catalyst Based on Silver Nanoparticles Mediating by the Root Extract of Bistorta amplexicaulis

Environmental pollution derivated from toxic metals and organic toxins is becoming a serious issue worldwide because of their harmful effects on the ecosystem and human health. Here we are reporting an extremely selective and cost-effective colorimetric sensor for simultaneous recognition of Hg2+ and Pb2+ by using green synthesized silver nanoparticles (AgNPs) mediated from the environmental friendly roots extract of Bistorta amplexicaulis. Biogenic synthesized AgNPs were well-characterized by various spectroscopic techniques e.g., UV-vis, FT-IR, XRD, AFM, and Zetasizer. The photophysical potential of synthesized AgNPs toward common metal cations was explored via absorption spectroscopy and colorimetric assay. The hypsochromic shift in the SPR band of AgNPs can easily be detected through naked eyes vision from dark brown to light yellow in the case of Hg2+. A substantial reduction in the absorbance of AgNPs was recorded upon mixing with Pb2+. AgNPs based colorimetric sensor is highly sensitive toward Hg2+ and Pb2+ with a limit of detection (LOD) of 8.0 × 10-7 M and 2.0 × 10-7 M for Hg2+ and Pb2+, respectively. Furthermore, AgNPs showed promising catalytic activity for the degradation of methyl orange dye. These results demonstrate that Bistorta amplexicaulis stabilized silver nanoparticles have potential applications as a colorimetric sensor and an effective catalyst for the degradation of methyl orange.