Portable Device with Nicking Enzyme Enhanced Special RCA on µPADs toward Sensitive Detection of High-Risk HPV Infection.

Development of an accurate, rapid, and cost-effective portable device is in high demand for point-of-care molecular diagnosis toward disease screening. Here we report a one-pot homogeneous isothermal assay that leverages nicking endonuclease and minimum secondary structured rolling circle amplification (N-MSSRCA) for fast and sensitive quantification of nucleic acids on distance microfluidic paper-based analytical devices (dµPAD) by a portable custom-made fluorescence detector. Human papillomavirus (HPV) oncogenic E7 mRNA as the biomarker for cervical cancer was used as the model analyte. N-MSSRCA integrates ligase for target recognition, the nicking enzyme for primer generation, and the dual function of the Phi29 DNA polymerase for both on- and off-loop amplification. The proposed method was capable of detecting 1 and 10 fM of the analyte using the microplate reader and portable detector with dµPAD, respectively, with ∼1 h assay time. A cohort study of 40 cervical swab samples shows N-MSSRCA reached positive and negative predictive values of 87.5% and 93.5% using the portable detector with dµPAD, compared to 91.67% and 100% using the microplate reader. N-MSSRCA demonstrates potential in early screening of high-risk HPV infection as a generic strategy to detect various nucleic acids in point-of-care scenarios.

Food additives: From functions to analytical methods.

Food additives refer to all kinds of trace substances used in food or food processing to preserve flavor or enhance food taste, appearance, or other qualities. At present, artificial synthetic food additives have gradually replaced the natural food additives and many problems related to food additives, involving the abuse of food additives, excessive additives or even toxic additives. Obviously, food additives can bring people great sensory enjoyment and commercial convenience, but they may also cause potential risks to human health. So, it is of high significance to conduct quantitative analysis on the content of food additives. According to their functions and the regulatory requirements of food additives, this review starts from the classification and structures of various food additives involving colorants, preservatives, antioxidants, sweeteners, emulsifiers, stabilizers, thickeners, gelling agents. It then summarizes and discusses analytical methods for quantification of food additives including modern immunoassays and other biotechnological methods. The proposed review aspires to fill in the knowledge gap of food additives between academia and industry by covering all kinds of analytical methods for quantifying food additives.