A simple and selective resonance Rayleigh scattering-energy transfer spectral method for determination of trace neomycin sulfate using Cu2O particle as probe

Colorimetric detection of neomycin sulfate in serum based on ultra-small gold nanoparticles with peroxidase-like activity

Neomycin sulfate (NEO) is a kind of aminoglycoside antibiotics. Because of its strong ototoxicity, nephrotoxicity and other side effects, its content in the body should be strictly monitored during use. In this paper, a rapid colorimetric detection method for NEO based on ultrasmall polyvinylpyrrolidone modified gold nanoparticles (PVP/Au NPs) with peroxidase-like activity was developed. Firstly, ultra small PVP/Au NPs with weak peroxidase-like activity were synthetized. When they were mixed with NEO, strong hydrogen bonds were formed between NEO and PVP, resulting in the aggregation of PVP/Au NPs, and the aggregated PVP/Au NPs showed stronger peroxidase-like activity. Therefore, rapid colorimetric detection of NEO was achieved by utilizing the enhanced peroxidase-like activity mechanism caused by the aggregation of ultra small PVP/Au NPs. The naked eye detection limit of this method is 50 nM. Within the range of 1 nM-300 nM, there was a good linear relationship between NEO concentration and the change in absorbance intensity of PVP/Au NPs-H2O2-TMB solution at 652 nm, with the regression curve of y = 0.0045x + 0.0525 (R2 = 0.998), and the detection limit is 1 nM. In addition, this method was successfully applied to the detection of NEO in mouse serum. The recoveries were 104.4 % -107.6 % compared with HPLC assay results, indicating that this method for NEO detection based on PVP/Au NPs has great potential in actual detection of NEO in serum.

Development and Biomedical Application of Non-Noble Metal Nanomaterials in SERS

Surface-enhanced Raman scattering (SERS) is vital in many fields because of its high sensitivity, fast response, and fingerprint effect. The surface-enhanced Raman mechanisms are generally electromagnetic enhancement (EM), which is mainly based on noble metals (Au, Ag, etc.), and chemical enhancement (CM). With more and more studies on CM mechanism in recent years, non-noble metal nanomaterial SERS substrates gradually became widely researched and applied due to their superior economy, stability, selectivity, and biocompatibility compared to noble metal. In addition, non-noble metal substrates also provide an ideal new platform for SERS technology to probe the mechanism of biomolecules. In this paper, we review the applications of non-noble metal nanomaterials in SERS detection for biomedical engineering in recent years. Firstly, we introduce the development of some more common non-noble metal SERS substrates and discuss their properties and enhancement mechanisms. Subsequently, we focus on the progress of the application of SERS detection of non-noble metal nanomaterials, such as analysis of biomarkers and the detection of some contaminants. Finally, we look forward to the future research process of non-noble metal substrate nanomaterials for biomedicine, which may draw more attention to the biosensor applications of non-noble metal nanomaterial-based SERS substrates.

Mxene Quantum Dot Nanosurface Molecularly Imprinted Polymer Resonance Rayleigh Scattering Probe for Highly Sensitive and Selective Determination of Thiocyanate

In this article, a nanosurface molecularly imprinted polymer (MQD@MIP) resonance Rayleigh scattering (RRS) spectral probe for SCN- was prepared by sol-gel method, using Mxene quantum dot as a matrix, thiocyanate (SCN-) as a template ion, (3-aminopropyl) triethoxysilane (APTES) as a functional monomer, tetraethoxysilane (TEOS) as the cross-linker, and ammonia as the initiator. The probe produced an RRS peak at 370 nm and exhibits a strong RRS energy transfer (RRS-ET) effect when the MQD@MIP probe identifies SCN-. As the concentration of SCN- increased, the RRS-ET was enhanced, and the signal value of the system decreased linearly at 370 nm, with a determination range of 0.87-5.22 μg/L, and a detection limit of 0.37 μg/L SCN-. This detection method has the characteristics of simplicity, sensitivity, and specific recognition. The RRS method was used to determine SCN- in the sample, with relative standard deviation of 1.95-10.98% and recovery of 89.0-102.8%.

Synthesis of cuprous oxide/silver (Cu2O/Ag) hybrid as surface-enhanced Raman scattering probe for trace determination of methyl orange

Recently, there have been publications on preparing hybrid materials between noble metal and semiconductor for applications in surface-enhanced Raman scattering (SERS) substrates to detect some toxic organic dyes. However, the use of cuprous oxide/silver (Cu₂O/Ag) to measure the trace amounts of methyl orange (MO) has not been reported. Therefore, in this study, the trace level of MO in water solvent was determined using a SERS substrate based on Cu₂O microcubes combined with silver nanoparticles (Ag NPs). Herein, a series of Cu₂O/Agx (x= 1-5) hybrids with various Ag amounts was synthesized via a solvothermal method followed by a reduction process, and their SERS performance was studied in detail. X-ray diffraction (XRD) and scanning electron microscopy results confirmed that 10 nm Ag NPs were well dispersed on 200-500 nm Cu₂O microcubes to form Cu₂O/Ag heterojunctions. Using the as-prepared Cu₂O and Cu₂O/Agx as MO probe, the Cu₂O/Ag5 nanocomposite showed the highest SERS activity of all samples with the limit of detection as low to 1 nM and the enhancement factor as high as 4 × 10⁸. The logarithm of the SERS peak intensity at 1389 cm^-1 increased linearly with the logarithm of the concentration of MO in the range from 1 nM to 0.1 mM.

Enhancement of Congo Red-Neomycin Resonance Rayleigh Scattering by Dodecyl Trimethyl Ammonium Bromide and its Application

A simple, rapid, and convenient method for the determination of neomycin based on the ion association method was proposed. In Britton–Robinson buffer solution, neomycin could react with Congo red to form an ionic association, which in turn reacted with dodecyl trimethyl ammonium bromide to form a ternary ionic association. The three were combined in a 1 : 1 : 1 ratio, which significantly enhanced the resonant Rayleigh scattering intensity at 468 nm. The obtained resonant Rayleigh scattering sensor showed a linear relationship with neomycin in the range of 0.07∼1 μg·mL⁻¹. The limit of detection was 0.02 μg·mL⁻¹, and the limit of quantification was 0.037 μg·mL⁻¹. The experimental conditions were optimized. The method was verified based on the ICH rule. The established method could be applied to the analysis of the acceptable recovery rate of neomycin in powdered veterinary drugs.

A cholesterol benzoate RRS probe for the determination of trace ammonium ions

The measurement of NH₄⁺ has attracted considerable attention with the increase of NH₄⁺ emissions in sewage caused by human activities. So far, a variety of photometric and fluorescence methods for the detection of NH₄⁺ have been researched and summarized, but there is no report about the use of liquid crystals (LCs) cholesteryl benzoate (CB) as a resonance Rayleigh scattering (RRS) probe to determine ammonium ions. In the NaAc-HAc buffer solution with pH = 4.80, the yellow compounds 3,5 diacetyl-1,4 dihydrolutidine (DDL) generated by the reaction of NH₄⁺ with acetylacetone (AT) and formaldehyde (HCHO) act as the energy receiver and CB as the donor. Because the RRS spectrum of CB overlaps with the DDL absorption spectrum, resonance Rayleigh scattering energy transfer (RRS-ET) occurs. When the NH₄⁺ concentration increased, the generated DDL increased, and the RRS-ET also increased, so the RRS intensity of the system at 395 nm decreased. For this reason, a fast and sensitive CB RRS-ET method was established to apply to the detection of NH₄⁺ in water. The detection range was 1.00 × 10^-3 - 4.66 μg/mL, and the detection limit was 6.62 × 10^-3 μg/mL. Using this method to analyze and detect NH₄⁺ in environmental water samples, the precision and recovery rate were between 1.30-9.30% and 95.5-109.9%, respectively. Therefore, this method has the advantages of sensitivity and simplicity.

Recent Advances in Optical Detection of Aminoglycosides

Aminoglycosides (AGs) are broad-spectrum antibiotics used in both human infection and animal medicine. The overuse of AGs causes undesirable residues in food, leading to serious health problems due to food chain accumulation. In recent years, various methods have been developed to determine AGs in food. Among these methods, fluorescent (FL), colorimetric and chemiluminescent (CL) optical methods possess advantages such as their simple instrumentation, low cost, simple operation, feasibility of realizing visualization, and smartphone imaging. This mini-review summarizes optical assays for the detection of AGs in food developed in recent years. The detection principles for different categories are discussed. Then, the amplification techniques for the ultrasensitive detection of AGs are introduced. We also discuss multiplex methods for the simultaneous detection of AGs. Finally, the challenges and future prospects are discussed in the Conclusions and Perspectives section.

The Growing Interest in Development of Innovative Optical Aptasensors for the Detection of Antimicrobial Residues in Food Products

The presence of antimicrobial residues in food-producing animals can lead to harmful effects on the consumer (e.g., allergies, antimicrobial resistance, toxicological effects) and cause issues in food transformation (i.e., cheese, yogurts production). Therefore, to control antimicrobial residues in food products of animal origin, screening methods are of utmost importance. Microbiological and immunological methods (e.g., ELISA, dipsticks) are conventional screening methods. Biosensors are an innovative solution for the development of more performant screening methods. Among the different kinds of biosensing elements (e.g., antibodies, aptamers, molecularly imprinted polymers (MIP), enzymes), aptamers for targeting antimicrobial residues are in continuous development since 2000. Therefore, this review has highlighted recent advances in the development of aptasensors, which present multiple advantages over immunosensors. Most of the aptasensors described in the literature for the detection of antimicrobial residues in animal-derived food products are either optical or electrochemical sensors. In this review, I have focused on optical aptasensors and showed how nanotechnologies (nanomaterials, micro/nanofluidics, and signal amplification techniques) largely contribute to the improvement of their performance (sensitivity, specificity, miniaturization, portability). Finally, I have explored different techniques to develop multiplex screening methods. Multiplex screening methods are necessary for the wide spectrum detection of antimicrobials authorized for animal treatment (i.e., having maximum residue limits).

Label free aptasensor for ultrasensitive detection of tobramycin residue in pasteurized cow's milk based on resonance scattering spectra and nanogold catalytic amplification

TOB aptamer can be adsorbed on the AuNPs surface to form AuNPs-aptamer complexation to prevent AuNPs aggregation in high salt solution. When TOB was added to the AuNPs solution, the aptamer would bind with TOB and depart from the AuNPs surface. The amount of the AuNPs-aptamer complexation depends on the TOB concentration. Different concentration of AuNPs-aptamer can catalyze the reduction reaction of CuSO₄ to produce different size Cu₂O particle. The resonance scattering peak intensities are correlated with the Cu₂O size. Large size Cu₂O particle as a resonance scattering spectroscopy probe can remarkable improve the TOB detection sensitivity. We have succeeded to detect the trace TOB in aqueous solutions. The linear range and limit of detection were 0.50-17 nM and 0.19 nM, respectively. This simple and inexpensive method exhibited high sensitivity and selectivity, which was successfully used to detect TOB in milk. The results indicated the accuracy and precision were satisfied.

Targeting and sensing of some cancer cells using folate bioreceptor functionalized nitrogen-doped graphene quantum dots

In recent years, study of folate receptor (FR) expression related to targeting, drug delivery and counting of tumoral cells have been followed. In this work, a fast and simple strategy was reported to determine the FR expressed cancer cells based on the selective bonding of the folic acid/folate (FA) to the FR-positive tumor cells. The folate decorated Nitrogen-doped graphene quantum dots (N-GQDs) were utilized as selective targeting of the MKN 45 cells. Fluorescent microscopy imaging investigations revealed that the produced FA conjugated N-GQDs could specifically attach to the target FR-positive tumor cells. Due to the fluorescence emission of N-GQDs, the developed cytosensor is free from attaching any fluorescent ligand i.e. Rhodamine B to capture the florescence microscopy images and also flow cytometry analysis. The fabricated cytosensor possesses a dynamic range from 100 to 7.0 × 10⁴ cell·mL^-1 with high selectivity. Furthermore, the cytosensor also could visualized the MCF 7 and HT 29 cells where the dynamic ranges were 100 to 1.0 × 10⁴ and 500 to 4.0 × 10⁴ cells·mL^-1, respectively. In vitro toxicity tests has shown low toxicity of the synthesized N-GQDs where the minimum viability is 68%. The proposed FA-N-GQDs based cytosensor provides a novel platform for detection of MKN 45, HT 29 and MCF 7 cancer cell lines which could be used in multi-channel cancer diagnosis biodevice.

A facile and highly sensitive resonance Rayleigh scattering-energy transfer method for urea using a fullerene probe

Under ultrasound conditions, a deep yellow fullerene (C₆₀) colloid was prepared, which exhibits two resonance Rayleigh scattering peaks at 385 nm and 530 nm. Urea was reacted with dimethylglyoxime (DMG) to produce 4,5-dimethyl-2-imidazole ketone (DIK), in the presence of stabilizer thiosemicarbazone (TSC). Resonance Rayleigh scattering energy transfer (RRS-ET) was shown to occur between the donor fullerene and acceptor DIK due to an overlap of the DIK absorption and fullerene RRS peaks. Upon an increase in the urea concentration, the RRS-ET was enhanced and the RRS intensity decreased. The decreased RRS intensity was linear to the urea concentration in the range of 6.66–333.00 nmoL L⁻¹, with a detection limit of 2.0 nmoL L⁻¹. Accordingly, a new and simple RRS-ET method was established for detecting trace levels of urea in foods, with satisfactory results.

Under ultrasound conditions, a deep yellow fullerene (C₆₀) colloid was prepared, which exhibits two resonance Rayleigh scattering peaks at 385 nm and 530 nm.