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Paper is a widely used support for use in devices for point-of-care testing (POCT) in clinical diagnosis, food safety monitoring and environmental pollution. Paper is inexpensive, biocompatible, biodegradable and allows a sample fluid to flow by capillary force. Numerous method have been developed recently for chemical modification of papers in order to introduce different functionalities. This review (with 148 refs.) summarizes the recent progress in paper-based POCT devices. The introduction summarizes the state of the art of paper-based POCT devices and the physicochemical properties of existing unmodified materials (including cellulose, cellulose-based composites, cotton fibers, glass fibers, nitrocellulose, thread). Methods for paper modification for sample pretreatment are summarized next, with subsections on sample storage and collection, sample separation, nucleic acid extraction and sample preconcentration. Another main section covers approaches for paper modification for improving POCTs, with subsections on assays for proteins, nucleic acids, drugs, ion and organic molecules. The advantages and disadvantages of these approaches are compared. Several tables are presented that summarize the various modification techniques. A concluding section summarizes the current status, addresses challenges and gives an outlook on future perspectives of POCTs.

BackgroundNudix hydrolases (Nd) is a widespread superfamily, which is found in all classes of organism, hydrolyse a wide range of organic pyrophosphates and has a ‘housecleaning’ function. The previous study showed that Trichinella spiralis Nd (TsNd) bound to intestinal epithelial cells (IECs), and the vaccination of mice with T7 phage-displayed TsNd polypeptides produced protective immunity. The aim of this study was to clone, express and identify the full-length TsNd and to investigate its immune protection against T. spiralis infection.MethodsThe full-length cDNA sequence of TsNd gene encoding a 46 kDa protein from T. spiralis intestinal infective larvae (IIL) was cloned and identified. The antigenicity of rTsNd was analyzed by Western blot. Transcription and expression of TsNd at T. spiralis different stages were observed by RT-PCR and IFT. The levels of the specific total IgG, IgG1 and IgG2a antibodies to rTsNd were determined by ELISA. The immune protection of rTsNd against T. spiralis infection was investigated.ResultsSequence and phylogenetic analysis revealed that TsNd had a nudix motif located at 226-244aa, which had high homology and the closest evolutionary status with T. pseudospiralis. The rTsNd was obtained after expression and purification. Western blot analysis showed that anti-rTsNd serum recognized the native TsNd protein in crude antigens of muscle larvae (ML), IIL, adult worms (AW) and newborn larvae (NBL), and ES antigens of ML. Transcription and expression of TsNd gene was observed in all developmental stages of T. spiralis (ML, IIL, AW and NBL), with high level expression in IIL. An immunolocalization analysis identified TsNd in the cuticle, stichocytes and reproductive organs of the parasite. Following immunization, anti-rTsNd IgG levels were increased, and the levels of IgG1 were more significantly higher than that of IgG2a. After a challenge infection with T. spiralis, mice immunized with the rTsNd displayed a 57.7% reduction in adult worms and a 56.9% reduction in muscle larval burden.ConclusionsTsNd induced a partial protective immunity in mice and could be considered as a novel candidate vaccine antigen against trichinellosis.