Circularly Polarized Light-Induced Chiral Growth of Achiral Plasmonic Nanoparticles Dispersed in a Solution.

Plasmonic nanoparticles (NPs) with chiral geometries have wide applications from chiral molecular sensing to enantioselective catalysis. The synthesis of chiral plasmonic nanoparticles using circularly polarized light (CPL) has attracted a considerable amount of attention because it eliminates the need for chiral molecules. However, NPs need to be immobilized on a solid substrate during synthesis. Here, we successfully synthesized colloidal chiral plasmonic NPs by depositing silver on the surface of achiral gold nanoparticles dispersed in a solution using CPL. Circular dichroism (CD) signals corresponding to the handedness of the irradiated CPL were observed when gold nanorods or gold nanotriangles were used. In contrast, no clear CD signal was observed when gold nanospheres were used. The morphological anisotropy of the gold nanoparticles was a key factor in the synthesis of chiral plasmonic nanoparticles using CPL. Furthermore, we demonstrated the tuning of chiroptical properties according to the CPL wavelength.

Comparison of three colloidal gold immunoassays and GeneXpert Carba-R for the detection of Klebsiella pneumoniae blaKPC-2 variants.

The increasing use of ceftazidime-avibactam has led to the emergence of a wide range of ceftazidime-avibactam-resistant blaKPC-2 variants. Particularly, the conventional carbapenemase phenotypic assay exhibited a high false-negative rate for KPC-2 variants. In this study, three colloidal gold immunoassays, including the Gold Mountainriver CGI test, Dynamiker CGI test and NG-Test CARBA5, and GeneXpert Carba-R, were used to detect the presence of KPC-2 carbapenemase and its various variants in 42 Klebsiella pneumoniae strains. These strains covered blaKPC-2 (13/42) and 16 other blaKPC-2 variants including blaKPC-12 (1/42), blaKPC-23 (1/42), blaKPC-25 (1/42), blaKPC-33 (6/42), blaKPC-35 (1/42), blaKPC-44 (1/42), blaKPC-71 (1/42), blaKPC-76 (8/42), blaKPC-78 (1/42), blaKPC-79 (1/42), blaKPC-100 (1/42), blaKPC-127 (1/42), blaKPC-128 (1/42), blaKPC-144 (1/42), blaKPC-157 (2/42), and blaKPC-180 (1/42). For KPC-2 strains, all four assays showed 100% negative percentage agreement (NPA) and 100% positive percentage agreement (PPA) with sequencing results. For all 16 KPC-2 variants, GeneXpert Carba-R showed 100% NPA and 100% PPA, and the three colloidal gold immunoassays showed 100% NPA, while the PPAs of the Gold Mountainriver CGI test, Dynamiker CGI test, and NG-Test CARBA5 were 87.5%, 87.5%, and 68.8%, respectively. We also found a correlation between the mutation site in the amino acid of the variants and false-negative results by colloidal gold immunoassays. In conclusion, the GeneXpert Carba-R has been proven to be a reliable method in detecting KPC-2 and its variants, and the colloidal gold immunoassay tests offer a practical and cost-effective approach for their detection. For the sample with a negative result by a colloidal gold immunoassay test but not matching the drug-resistant phenotype, it is recommended to retest using another type of kit or the GeneXpert Carba-R assay, which can significantly improve the accuracy of detection.

An experimental study on the visual identification of Fritillaria ussuriensis based on LAMP and nucleic acid colloidal gold technique.

Fritillaria ussuriensis Maxim is one of the traditional Chinese valuable herbs, which is the dried bulb of Fritillaria, a plant of the lily family. The identification of authenticity about F. ussuriensis is still technically challenging. In this study, visual identification was performed by ring-mediated isothermal amplification and nucleic acid colloidal gold techniques. Firstly, multiple sequence comparative analysis was performed by DNAMAN to find the differential sites of F. ussuriensis and its mixed pseudo-products, and the specific identification primers of F. ussuriensis were designed. Genomic DNA was extracted by the modified CTAB method, and the reaction system and reaction conditions were optimized to construct LAMP for the visual detection of F. ussuriensis, meanwhile, the genuine product was cloned and the extracted plasmid was sequenced. The specificity and sensitivity were detected, and also verified by nucleic acid colloidal gold method, and 20 commercially available samples were tested. The extracted DNA met the requirements of the experiment, and the genuine F. ussuriensis PCR product titrated on a test strip showed two bands on the T and C lines, while the counterfeit and negative control showed only one band on the C line, which matched the LAMP results. The specificity was 100 %, and the sensitivity of LAMP assay was up to 0.01 ng µL-1, while that of colloidal gold assay was 0.1 ng µL-1, thus the LAMP assay had high sensitivity. 14 out of 20 commercially available samples of F. ussuriensis were qualified, and 6 were unqualified, and the results of the two methods of identification were consistent. In this study, the combined detection method of LAMP and colloidal gold for nucleic acid was established to be specific, rapid, precise and visualized, which can provide a new technical idea for the detection of F. ussuriensis.

Development and application of a colloidal-gold immunochromatographic strip for detecting Getah virus antibodies.

Getah virus (GETV) is a re-emerging mosquito-borne alphavirus that is highly pathogenic, mainly to pigs and horses. There are no vaccines or treatments available for GETV in swine in China. Therefore, the development of a simple, rapid, specific, and sensitive serological assay for GETV antibodies is essential for the prevention and control of GETV. Current antibody monitoring methods are time-consuming, expensive, and dependent on specialized instrumentation, and these features are not conducive to rapid detection in clinical samples. To address these problem, we developed immunochromatographic test strips (ICTS) using eukaryotically expressed soluble recombinant p62-E1 protein of GETV as a labelled antigen, which has good detection sensitivity and no cross-reactivity with other common porcine virus-positive sera. The ICTS is highly compatible with IFA and ELISA and can be stored for 1 month at 37 °C and for at least 3 months at room temperature. Hence, p62-E1-based ICTS is a rapid, accurate, and convenient method for rapid on-site detection of GETV antibodies. KEY POINTS: • We established a rapid antibody detection method that can monitor GETV infection • We developed colloidal gold test strips with high sensitivity and specificity • The development of colloidal gold test strips will aid in the field serologic detection of GETV.

Development and evaluation of a test strip for the rapid detection of antibody against equine infectious anemia virus.

Equine infectious anemia (EIA) is a contagious disease of horses caused by the equine infectious anemia virus (EIAV). The clinical signs at the acute phase include intermittent high fever, thrombocytopenia, hemorrhage, edema, and anemia. The clinical signs at chronic and relapsing subclinical levels include emaciation and progressive weakness. Surviving horses become lifelong carriers because of the integration of the viral genome into that of the host, and these horses can produce and transmit the virus to other animals. This increases the difficulty of imposing practical control measures to prevent epidemics of this disease. Serological tests measuring the antibodies in equine sera are considered to be a reliable tool for the long-term monitoring of EIA. However, the standard serological tests for EIV either have low sensitivity (e.g., agar gel immunodiffusion test, AGID) or are time consuming to perform (e.g., ELISA and western blotting). The development of a rapid and simple method for detecting the disease is therefore critical to control the spread of EIA. In this study, we designed and developed a colloidal gold immunochromatographic (GICG) test strip to detect antibodies against EIAV based on the double-antigen sandwich. Both the p26 and gp45 proteins were used as the capture antigens, which may help to improve the positive detection rate of the strip. We found that the sensitivity of the test strip was 8 to 16 times higher than those of two commercially available ELISA tests and 128 to 256 times higher than AGID, but 8 to 16 times lower than that of western blotting. The strip has good specificity and stability. When serum samples from experimental horses immunized with the attenuated EIAV vaccine (n = 31) were tested, the results of the test strip showed 100% coincidence with those from NECVB-cELISA and 70.97% with AGID. When testing clinical serum samples (n = 1014), the test strip surprisingly provided greater sensitivity and a higher number of "true positive" results than other techniques. Therefore, we believe that the GICG test strip has demonstrated great potential in the field trials as a simple and effective tool for the detection of antibodies against EIAV. KEY POINTS: • A colloidal gold immunochromatographic (GICG) fast test strip was developed with good specificity, sensitivity, stability, and repeatability • The test strip can be used in point-of-care testing for the primary screening of EIAV antibodies • Both the p26 and gp45 proteins were used as the capture antigens, giving a high positive detection rate in the testing of experimentally infected animal and field samples.

Development of polymerase chain reaction-lateral flow dipstick assay for detection of Mycoplasma bovis in cattle.

Mycoplasma bovis (M. bovis) is capable of causing a range of diseases in cattle, encompassing calf pneumonia, arthritis, conjunctivitis, meningitis, and mastitis. It is widely recognized as one of the predominant pathogens posing a significant threat to the global cattle industry. Therefore, accurate and sensitive methods are urgently needed to detect M. bovis. This study aims to detect M. bovis by combining colloidal gold with biotin-labeled oligonucleotides to improve detection sensitivity and form a chromogenic detection probe based on signal amplification technology. Here, we developed a sensitive and specific polymerase chain reaction-lateral flow dipstick assay (PCR-LFD) strip for efficient nucleic acid detection of M. bovis. A pair of specific primers with 5' ends labeled with biotin and digoxigenin probes was designed for PCR experiments. Colloidal gold particles-labeled anti-digoxigenin IgG coated gold-labeled test strip was prepared, streptavidin was used as the detection probe, and nitrocellulose membrane coated goat anti-mouse IgG was used as the control line. Our results showed that the detection limit of the PCR-LFD was 89 fg/µL for the M. bovis DNA. The results from the test strip were highly consistent with those from real-time qPCR. This assay were highly specific for M. bovis, as there were no cross-reactions with other microorganisms tested and the detection sensitivity of the test was also relatively high (97.67%). The novel strips present a promising tool for the cost-effective and sensitive diagnosis of M. bovis.

Study on the performance of novel nanomaterials for detection of biomarkers such as PCT based on immunochromatography sensitivity.

In this study, by comparing the UV-vis spectral characteristics of colloidal gold and colloidal gold enhancer, and their differences as immunochromatographic tracers in the qualitative detection of PCT, IL-6, Hp and quantitative determination of PCT performance, the factors that may affect the sensitivity were discussed. The results show that the absorbance at 520 nm of CGE diluted 20-fold and colloidal gold diluted 2-fold were comparable, and the sensitivity of CGE immunoprobe for qualitative detection of PCT, IL-6 and Hp was higher than that of colloidal gold immunoprobe, and the reproducibility and accuracy of both immunoprobes for quantitative detection of PCT were good. Indicating that the high sensitivity of CGE immunoprobe detection is mainly due to the absorption coefficient of CGE at 520 nm is about 10 times that of colloidal gold immunoprobe, CGE has stronger light absorption capacity and stronger quenching effect on rhodamine 6 G on the nitrocellulose membrane surface of the test strip.

Colloidal gold and fluorescent immunochromatographic test strips for canine parvovirus detection.

Canine parvovirus (CPV) is an acute and highly infectious virus causing disease in puppies and, thus, affecting the global dog industry. The current CPV detection methods are limited by their sensitivity and specificity. Hence, the current study sought to develop a rapid, sensitive, simple, and accurate immunochromatographic (ICS) test to detect and control the spread and prevalence of CPV infection. More specifically, 6A8, a monoclonal antibody (mAb) with high specificity and sensitivity, was obtained by preliminary screening. The 6A8 antibody was labelled with colloidal gold particles. Subsequently, 6A8 and goat anti-mouse antibodies were coated onto a nitrocellulose membrane (NC) as the test and control lines, respectively. Furthermore, 6A8 and rabbit IgG antibodies were labelled with fluorescent microspheres and evenly sprayed onto a glass fibre membrane. Both strips could be prepared in 15 min with no noticeable cross-reactivity with other common canine intestinal pathogens. The strips were simultaneously used to detect CPV in 60 clinical samples using real-time quantitative PCR, hemagglutination, and hemagglutination inhibition assays. The colloidal gold (fluorescent) ICS test strip was stable for 6 (7) and 4 (5) months at 4 °C and room temperature (18-25 °C). Both test strips were easy to prepare and rapidly detected CPV with high sensitivity and specificity. Moreover, the results were easily interpretable. This study establishes a simple method for two CPV diseases, colloidal gold and fluorescent immunochromatographic (ICS) test strips. KEY POINTS: • CPV test strips do not exhibit cross-reactivity with other canine intestinal pathogens. • The strips are stable for months at 4 °C and at room temperature (18-25 °C). • These strips are a promising approach for the timely diagnosis and treatment of CPV.

Rapid Colloidal Gold Immunoassay for Pharmacokinetic Evaluation of Vancomycin in the Cerebrospinal Fluid and Plasma of Beagle Dogs.

Vancomycin (VAN), a glycopeptide antibiotic, is the preferred therapeutic agent for treating Gram-positive bacteria. Rapid and precise quantification of VAN levels in cerebrospinal fluid (CSF) and plasma is crucial for optimized drug administration, particularly among elderly patients. Herein, we introduce a novel clinical test strip utilizing colloidal gold competitive immunoassay technology for the expedient detection of VAN. This test strip enables the detection of VAN concentrations in clinical samples such as plasma within 10 min and has a limit of detection of 10.3 ng/mL, with an inhibitory concentration 50% (IC50) value of 44.5 ng/mL. Furthermore, we used the test strip for pharmacokinetic analysis of VAN in the CSF and plasma of beagle dogs. Our results provide valuable insights into the fluctuations of the drug concentration in the CSF and plasma over a 24 h period after a single intravenous dose of 12 mg/kg. The test strip results were compared with the results obtained via liquid chromatography-mass spectrometry methods, and the measured VAN concentrations in the CSF and plasma via both of the methods showed excellent agreement.

[Features of Production Process and Risk Prevention and Control Points of Corona Virus Disease 2019 (2019-nCoV) Antigen Detection Reagent (Colloidal Gold Method)].

Corona Virus Disease 2019 (2019-nCoV) antigen detection reagent (colloidal gold method) has been applied to people who go to basic medical and health institutions for medical treatment and have respiratory tract, fever and other symptoms within 5 days, isolate observers, community residents who need antigen self-testing. The wide application of the reagent can effectively shorten the detection time, reduce the detection cost and time cost, and alleviate the pressure of nucleic acid detection. The article details the structural components, testing principles, production process and key risk points of the new coronavirus antigen test reagents, with the aim of providing a reference for the development of relevant work specifications for manufacturers, the organization of safe production and the verification and supervision of regulatory authorities.

Preparation of highly specific monoclonal antibodies against SARS-CoV-2 nucleocapsid protein and the preliminary development of antigen detection test strips.

The coronavirus disease 2019 (COVID-19) is outbreaking all over the world. To help fight this disease, it is necessary to establish an effective and rapid detection method. The nucleocapsid (N) protein of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is involved in viral replication, assembly, and immune regulation and plays an important role in the viral life cycle. Moreover, the N protein also could be a diagnostic factor and potential drug target. Therefore, by synthesizing the N gene sequence of SARS-CoV-2, constructing the pET-28a (+)-N recombinant plasmid, we expressed the N protein in Escherichia coli and obtained 15 monoclonal antibody (mAbs) against SARS-CoV-2-N protein by the hybridomas and ascites, then an immunochromatographic test strip method detecting N antigen was established. In this study, we obtained 14 high-titer and high-specificity monoclonal antibodies, and the test strips exclusively react with the SARS-CoV-2-N protein and no cross-reactivity with other coronavirus and also recognize the recombinant N protein of Delta (B.1.617.2) variant. These mAbs can be used for the early and rapid diagnosis of SARS-CoV-2 infection through serological antigen.

Highly sensitive interleukin 6 detection by employing commercially ready liposomes in an LFA format.

Recent years have confirmed the ubiquitous applicability of lateral flow assays (LFA) in point-of-care testing (POCT). To make this technology available for low abundance analytes, strategies towards lower limits of detections (LOD), while maintaining the LFA's ease of use, are still being sought. Here, we demonstrate how liposomes can significantly improve the LOD of traditional gold nanoparticle (AuNP)-based assays while fully supporting a ready-to-use system for commercial application. We fine-tuned liposomes towards photometric and fluorescence performance on the synthesis level and applied them in an established interleukin 6 (IL-6) immunoassay normally using commercial AuNP labels. IL-6's low abundance (< 10 pg mL-1) and increasing relevance as prognostic marker for infections make it an ideal model analyte. It was found that liposomes with a high encapsulant load (150 mmol L-1 sulforhodamine B (SRB)) easily outperform AuNPs in photometric LFAs. Specifically, liposomes with 350 nm in diameter yield a lower LOD even in complex matrices such as human serum below the clinically relevant range (7 pg mL-1) beating AuNP by over an order of magnitude (81 pg mL-1). When dehydrated on the strip, liposomes maintained their signal performance for over a year even when stored at ambient temperature and indicate extraordinary stability of up to 8 years when stored as liquid. Whereas no LOD improvement was obtained by exploiting the liposomes' fluorescence, an extraordinary gain in signal intensity was achieved upon lysis which is a promising feature for high-resolution and low-cost detection devices. Minimizing the procedural steps by inherently fluorescent liposomes, however, is not feasible. Finally, liposomes are ready for commercial applications as they are easy to mass-produce and can simply be substituted for the ubiquitously used AuNPs in the POCT market.

Development of a p72 trimer-based colloidal gold strip for detection of antibodies against African swine fever virus.

African swine fever virus (ASFV) causes a highly contagious and often lethal swine viral disease, and leads to tremendous economic losses to the swine industry. Unfortunately, there are no vaccines and effective antiviral agents available to prevent and control ASFV outbreaks. Therefore, it is necessary to develop simple and rapid strategies to monitor ASFV-infected pigs to restrain its spread. In the current study, ASFV capsid protein p72 was expressed along with its chaperone pB602L to form trimers in human embryonic kidney 293 (HEK293) cells. The p72 trimers were subsequently labeled with colloidal gold to develop a immunochromatographic strip. The strip showed high specificity to ASFV-positive serum and no cross-reactivity to other swine virus positive sera. Importantly, the strip showed a higher sensitivity of detecting ASFV antibodies in both positive standard serum and clinical serum samples than a commercial enzyme-linked immunosorbent assay (ELISA) kit. Taken together, these results demonstrate the strip as a reliable diagnostic tool against ASFV infection, which will be appropriate for application in prevention and control of ASFV. KEY POINTS : • ASFV p72 trimers were successfully generated. • A colloidal gold strip was developed based on ASFV p72 trimers. • The strip is appropriate for detecting ASFV antibodies in the field.

Development and application of a colloidal-gold dual immunochromatography strip for detecting African swine fever virus antibodies.

African swine fever (ASF) is an acute and highly contagious infectious disease caused by the African swine fever virus (ASFV). Currently, there is no vaccine against ASF worldwide, and no effective treatment measures are available. For this reason, developing a simple, rapid, specific, and sensitive serological detection method for ASFV antibodies is crucial for the prevention and control of ASF. In this study, a 1:1 mixture of gold-labeled p30 and p72 probes was used as the gold-labeled antigen. The p30 and p72 proteins and their monoclonal antibodies were coated on a nitrocellulose membrane (NC) as a test (T) line and control (C) line, respectively. A colloidal-gold dual immunochromatography strip (ICS) for ASFV p30 and p72 protein antibodies was established. The results showed that the colloidal-gold dual ICS could specifically detect ASFV antibodies within 5-10 min. There was no cross-reaction after testing healthy pig serum; porcine reproductive and respiratory syndrome virus (PRRSV), foot-and-mouth disease type A virus (FMDV-A), foot-and-mouth disease type O virus (FMDV-O), porcine circovirus type 2 (PCV-2), and classical swine fever virus (CSFV) positive sera. A positive result was obtained only for the positive control P1. The sensitivity of the test strips was 1:256, which was equivalent to that of commercially ELISA kits. Their coincidence rate with the two commercial ASFV ELISA antibodies detection kits was higher than 98%. The test strips were stably stored at 18-25 °C and 4 °C for 4 and 6 months, respectively. The colloidal-gold dual ICS prepared in this study had high sensitivity and specificity and were characterized by rapid detection, simple operation, and easy interpretation of results. Therefore, they are of great significance to diagnose, prevent, and control African swine fever. KEY POINTS: • We establish an antibody detection that is quick and can monitor an ASF infection. • We observe changes in two protein antibodies to dynamically monitor ASF infection. • We use diversified detection on a single test strip to detect both antibodies.

Analysis of 4 cases of children with false-positive results of novel coronavirus-specific antibody.

BACKGROUND: This study attempts to explore the influencing factors and solutions of the colloidal gold method for novel coronavirus (2019-nCoV)-specific IgM/IgG antibody detection, summarize the clinical experience and perfect the examination process, improving the application value of antibody detection in COVID-19 diagnosis. METHODS: A total of 13,329 peripheral whole blood/plasma/serum samples were obtained for COVID-19 screening from children who visited the Children's Hospital of the Capital Institute of Pediatrics outpatient clinic from April 22, 2020, to November 30, 2020. The colloidal gold method was adopted for 2019-nCoV-specific IgM/IgG antibody detection. The virus nucleic acid test results, clinical records, and serum protein fingerprint results of antibody-positive patients were collected. RESULTS: All samples were examined using the colloidal gold method with two 2019-nCoV-specific IgM/IgG antibody detection kits. Four patients were tested single antibody-positive using both kits. The details were as follows: two cases of IgM ( +) and IgG (-) using plasma and serum separately, two cases of IgM (-) and IgG ( +) using serum and whole blood. The protein fingerprinting results and nucleic acid tests of 2019-nCoV antibodies were negative in the 4 cases. Considering the epidemiological history, clinical manifestations, and test results, these 4 children were ruled out for 2019-nCoV infection. CONCLUSIONS: When the colloidal gold method was used to detect 2019-nCoV-specific IgM/IgG antibodies, it was important to ascertain the test results as precisely as possible. Specimen type and patient history may interfere with the diagnosis.

Photothermal card reader assay using the commercial colloidal gold test strip for the rapid quantitative detection of food hazards.

The simple and rapid commercial colloidal gold test strip can only be used for qualitative or semi-quantitative detection, accompanied by weak detectability and false negative experimental results. Herein, a photothermal test strip assay which combined test strip with a portable photothermal card reader was established to achieve quantitative detection with excellent detectability. According to the photothermal effect produced by gold nanoparticles (GNPs) captured on the test line, the signal could be recorded by the reader. Thirteen food hazards including veterinary drug residues and pesticide residues were tested; the photothermal detectability in actual samples were about 23 (methyl parathion), 7 (enrofloxacin), 6 (sarafloxacin), 8 (sulfadiazine), 12 (sulfamethazine), 7 (paraquat), 6 (malachite green), 11 (amantadine), 13 (nitrofurazone), 6 (diethylstilbestrol), 12 (estriol), 21 (estrone), and 26 (17ß-estradiol) times better than the visual detectability. Our results demonstrated that the photothermal test strip assay could be used for sensitive, rapid, and quantitative detection of residues of food hazards.

Lateral Flow Test System to Control Total Content of Muscle Tissues in Raw Meat Products.

Assessment of the composition of meat-containing products is the task in demand due to their frequent deviations from declared recipes. The paper presents the developed test system for immunochromatographic determination of total meat content. The assay is based on the simultaneous use of monoclonal antibodies, which specifically interacts with mammalian skeletal troponin I, and polyclonal antibodies, which specifically detect bird immunoglobulin Y. To integrate the detection of both types of meat by the same test strip, the antibodies are mixed in the analytical zone of the test strip and in complex with a gold nanoparticle label. The chosen ratios of the antibodies for both mixtures provide the same contribution of different types of mammalian and bird raw materials of muscle tissues to the label binding. The test system demonstrates suitability for products containing beef, pork, rabbit, lamb, chicken, and turkey meat. The minimal detectable content of meat in samples is 0.1%. The samples for the testing are diluted 100 times, thus eliminating matrix effects, and providing high reproducibility of the color intensity for extracts of different compositions. The obtained results allow the recommendation of the developed test system for rapid on-site control of meat products.

Antioxidant and Anti-Melanogenesis Effects of Colloidal Gold Camellia sinensis L. Extracts.

Green tea extract derived from the leaves of Camellia sinensis L. (CS), is a representative beverage with antioxidant, anti-cancer, and anti-viral properties. CS extract is also used in cosmetics. Colloidal gold is generally a sol or colloidal suspension of gold nanoparticles in water. Colloidal gold green tea (CGCS), cultivated as a fertilizer using this colloidal gold solution, contains gold minerals and possesses anti-inflammatory, analgesic, and anti-tumor properties. However, the skin bioactivity of CGCS has not yet been investigated. In this study, we investigated the effect of the CGCS extract on skin whitening. CGCS extract contained high levels of phenols and flavonoids and displayed 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity in a concentration-dependent manner. CGCS extract inhibited melanin synthesis and tyrosinase activity in B16F10 cells more effectively than the CS extract. Moreover, the CGCS extract decreased the expression levels of the melanogenesis-related proteins, tyrosinase, tyrosinase-related proteins (TRPs), and microphthalmia-associated transcription factor (MITF). In conclusion, our study showed that the CGCS extract inhibits the expression of tyrosinase, TRP-1, and TRP-2 via the downregulation of MITF, thereby inhibiting melanin synthesis. Therefore, CGCS can potentially be used as a skin-whitening ingredient in the cosmetic industry.

Dummy Template-Based Molecularly Imprinted Membrane Coating for Rapid Analysis of Malachite Green and Its Metabolic Intermediates in Shrimp and Fish.

A novel malachite green molecularly imprinted membrane (MG-MIM) with specific selectivity for malachite green (MG) and leucomalachite green (LMG) was prepared using a hydrophobic glass fiber membrane as the polymer substrate, methyl violet as a template analog, 4-vinyl benzoic acid as the functional monomer, and ethyleneglycol dimethacrylate as the crosslinking agent. MG-MIM and non-imprinted membrane (NIM) were structurally characterized using scanning electron microscopy, surface area analyzer, Fourier-transform infrared spectrometer and synchronous thermal analyzer. The results showed that MG-MIM possessed a fluffier surface, porous and looser structure, and had good thermal stability. Adsorption properties of MG-MIM were investigated under optimal conditions, and adsorption equilibrium was reached in 20 min. The saturated adsorption capacities for MG and LMG were 24.25 ng·cm-2 and 13.40 ng·cm-2, and the maximum imprinting factors were 2.41 and 3.20, respectively. Issues such as "template leakage" and "embedding" were resolved. The specific recognition ability for the targets was good and the adsorption capacity was stable even after five cycles. The proposed method was successfully applied for the detection of MG and LMG in real samples, and it showed good linear correlation in the range of 0 to 10.0 µg·L-1 (R2 = 0.9991 and 0.9982), and high detection sensitivity (detection limits of MG and LMG of 0.005 µg/kg and 0.02 µg·kg-1 in shrimp, and 0.005 µg/kg and 0.02 µg/kg in fish sample). The recoveries and relative standard deviations were in the range of 76.31-93.26% and 0.73-3.72%, respectively. The proposed method provides a simple, efficient and promising alternative for monitoring MG and LMG in aquatic products.

Development of a colloidal gold immunochromatographic strip for the rapid detection of pefloxacin in grass carp with a novel pretreatment method.

A rapid colloidal gold immunochromatography assay (GICA) for the detection of pefloxacin (PEF) was established and optimized. The anti-PEF monoclonal antibody (mAb) was used to target PEF as a colloidal gold-mAb conjugate. The mAb belonged to the IgG2b subtype, lambda light chain, the affinity constant (Ka) was 5.21 × 109 L·mol-1, and its half maximal inhibitory concentration (IC50) was 0.23 ng·mL-1. No obvious cross-reactivity (CR) was observed with other common fluoroquinolone antibiotics, including ciprofloxacin (CIP), norfloxacin (NOR), lomefloxacin (LOM) and ofloxacin (OFL). The visual limit of detection (vLOD) of the optimized GICA was 2 ng·g-1 under the conventional pretreatment method, and the assay was completed in 15 min. Liquid chromatography tandem-mass spectrometry (LC-MS/MS) was employed to confirm the performance of the strip. In addition, a novel pretreatment was established and compared with conventional pretreatment. Without the removal of organic solvents, the novel pretreatment method reduced the sample pretreatment time (more than 10 min). The vLOD of the optimized GICA was also 2 ng·g-1 when applying the novel pretreatment method. In conclusion, the proposed PEF-GICA could detect samples containing PEF rapidly and accurately, and the novel pretreatment method saved the time of sample pretreatment and improved the efficiency of detection.