Surface-enhanced resonance Raman scattering (SERRS) simulates PCR for sensitive DNA detection

Comprehensive review of conventional and state-of-the-art detection methods of Cryptosporidium

Cryptosporidium is a critical waterborne protozoan pathogen found in water resources that have been a major cause of death and serious illnesses worldwide, costing millions of dollars annually for its detection and treatment. Over the past several decades, substantial efforts have been made towards developing techniques for the detection of Cryptosporidium. Early diagnostic techniques were established based on the existing tools in laboratories, such as microscopes. Advancements in fluorescence microscopy, immunological, and molecular techniques have led to the development of several kits for the detection of Cryptosporidium spp. However, these methods have several limitations, such as long processing times, large sample volumes, the requirement for bulky and expensive laboratory tools, and the high cost of reagents. There is an urgent need to improve these existing techniques and develop low-cost, portable and rapid detection tools for applications in the water quality industry. In this review, we compare recent advances in nanotechnology, biosensing and microfluidics that have facilitated the development of sophisticated tools for the detection of Cryptosporidium spp.Finally, we highlight the advantages and disadvantages, of these state-of-the-art detection methods compared to current analytical methodologies and discuss the need for future developments to improve such methods for detecting Cryptosporidium in the water supply chain to enable real-time and on-site monitoring in water resources and remote areas.

Fuzzy characterization and classification of bacteria species detected at single-cell level by surface-enhanced Raman scattering

Advanced chemometric methods, such as fuzzy c-means, a semi-supervised clustering method, and fuzzy linear discriminant analysis (FLDA), a new robust supervised classification method in combination with principal component analysis (PCA), namely PCA-FLDA, have been successfully applied for characterization and classification of bacterial species detected at single-cell level by surface-enhanced Raman scattering (SERS) spectroscopy. SERS spectra of three species (S. aureus, E. faecalis and P. aeruginosa) were recorded in an original fashion, using in situ laser induced silver spot as metallic substrate. The detection process of bacteria was isolated inside a hermetically sealed in-house built microfluidic device, connected to a syringe pump for injecting the analytes and a portable Raman spectrometer as detection tool. The obtained results (fuzzy partitions) and spectra of the prototypes (robust fuzzy spectra mean corresponding to each fuzzy partition) clearly demonstrated the efficiency and information power of the advanced fuzzy methods in bacteria characterization and classification based on SERS spectra, and allowed a rationale assigning to a specific group. Also, this powerful detection and classification methodology generates the premises for future investigations of Raman and other spectroscopic data obtained for various samples.

Sensitive and Direct DNA Mutation Detection by Surface-Enhanced Raman Spectroscopy Using Rational Designed and Tunable Plasmonic Nanostructures

Efficient DNA mutation detection methods are required for diagnosis, personalized therapy development, and prognosis assessment for diseases such as cancer. To address this issue, we proposed a straightforward approach by combining active plasmonic nanostructures, surface-enhanced Raman spectroscopy (SERS), and polymerase chain reaction (PCR) with a statistical tool to identify and classify BRAF wild type (WT) and V600E mutant genes. The nanostructures provide enhanced sensitivity, while PCR offers high specificity toward target DNA. A series of positively charged plasmonic nanostructures including gold/silver nanospheres, nanoshells, nanoflowers, and nanostars were synthesized with a one-pot strategy and characterized. By changing the shape of nanostructures, we are able to vary the surface plasmon resonance from 551 to 693 nm. The gold/silver nanostar showed the highest SERS activity, which was employed for DNA mutation detection. We reproducibly analyzed as few as 100 copies of target DNA sequences using gold/silver nanostars, thus demonstrating the high sensitivity of the direct SERS detection. By means of statistical analysis (principal component analysis-linear discriminant analysis), this method was successfully applied to differentiate the WT and V600E mutant both from whole genome DNA lysed from cell line and from cell-free DNA collected from cell culture media. We further proved that this assay is capable of specifically amplifying and accurately classifying a real plasma sample. Thus, this direct SERS strategy combined with the active plasmonic nanostructures has the potential for wide applications as an alternative tool for sensitively monitoring and evaluating important clinical nucleotide biomarkers.

Surface enhanced Raman spectroscopy: A review of recent applications in forensic science

Surface enhanced Raman spectroscopy has many advantages over its parent technique of Raman spectroscopy. Some of these advantages such as increased sensitivity and selectivity and therefore the possibility of small sample sizes and detection of small concentrations are invaluable in the field of forensics. A variety of new SERS surfaces and novel approaches are presented here on a wide range of forensically relevant topics.

Nanoporous anodic aluminum oxide internalized with gold nanoparticles for on-chip PCR and direct detection by surface-enhanced Raman scattering

Nanoporous anodic aluminum oxide (AAO) internalized with gold nanoparticles was utilized as an integrated platform miniaturized for consecutively performing on-chip PCR and downstream detection of the target DNA amplicons using surface-enhanced Raman scattering (SERS).

Gigantol from Dendrobium chrysotoxum Lindl. binds and inhibits aldose reductase gene to exert its anti-cataract activity: An in vitro mechanistic study

ETHNOPHARMACOLOGICAL RELEVANCE

Dendrobium. chrysotoxum Lindl is a commonly used species of medicinal Dendrobium which belongs to the family of Orchidaceae, locally known as "Shihu" or "Huangcao". D. chrysotoxum Lindl is widely known for medicinal values in traditional Chinese medicine as it possesses anti-inflammatory, anti-hyperglycemic induction, antitumor and antioxidant properties.

STUDY AIM

To characterize the interaction between gigantol extracted from D. chrysotoxum Lindl and the AR gene, and determine gigantol's efficacy against cataractogenesis.

MATERIALS AND METHODS

Human lens epithelial cells (HLECs) were induced by glucose as the model group. Reverse transcription polymerase chain reaction (RT-PCR) was used to assess AR gene expression. Then, the mode of interaction of gigantol with the AR gene was evaluated by UV-visible spectroscopy, atomic force microscope (AFM) and surface-enhanced Raman spectroscopy (SERS). The binding constant was determined by UV-visible.

RESULTS

Gigantol depressed AR gene expression in HLECs. UV-visible spectra preliminarily indicated that interaction between the AR gene and gigantol may follow the groove mode, with a binding constant of 1.85×10³L/mol. Atomic force microscope (AFM) data indicated that gigantol possibly bound to insert AR gene base pairs of the double helix. Surface-enhanced Raman spectroscopy (SERS) studies further supported these observations.

CONCLUSION

Gigantol extracted from D. chrysotoxum Lindl not only has inhibitory effects on aldose reductase, but also inhibits AR gene expression. These findings provide a more comprehensive theoretical basis for the use of Dendrobium for the treatment of diabetic cataract.

Simple, Sensitive and Accurate Multiplex Detection of Clinically Important Melanoma DNA Mutations in Circulating Tumour DNA with SERS Nanotags

Sensitive and accurate identification of specific DNA mutations can influence clinical decisions. However accurate diagnosis from limiting samples such as circulating tumour DNA (ctDNA) is challenging. Current approaches based on fluorescence such as quantitative PCR (qPCR) and more recently, droplet digital PCR (ddPCR) have limitations in multiplex detection, sensitivity and the need for expensive specialized equipment. Herein we describe an assay capitalizing on the multiplexing and sensitivity benefits of surface-enhanced Raman spectroscopy (SERS) with the simplicity of standard PCR to address the limitations of current approaches. This proof-of-concept method could reproducibly detect as few as 0.1% (10 copies, CV < 9%) of target sequences thus demonstrating the high sensitivity of the method. The method was then applied to specifically detect three important melanoma mutations in multiplex. Finally, the PCR/SERS assay was used to genotype cell lines and ctDNA from serum samples where results subsequently validated with ddPCR. With ddPCR-like sensitivity and accuracy yet at the convenience of standard PCR, we believe this multiplex PCR/SERS method could find wide applications in both diagnostics and research.