title: Smartphone-based enzymatic biosensor for oral fluid L-lactate detection in one minute using confined multilayer paper reflectometry.
abstract: The development of smartphone-based biosensors for point-of-care testing (POCT) applications allows realizing "all in one" instruments, with large potential distribution among the general population. With this respect, paper color-based detection performed by reflectance measurement is the most popular, simple, inexpensive and straightforward method. Despite the large number of scientific publications related to these biosensors, they still suffer from a poor detectability and reproducibility related to inhomogeneity of color development, which leads to low assay reproducibility. To overcome these problems, we propose a smartphone paper-based biosensor, in which all the reagents necessary to complete the analysis are co-entrapped on paper in a "wafer"-like bilayer film of polyelectrolytes (Poly (allyl amine hydrochloride/poly(sodium 4-styrene sulfonate)). Using a 3D printing low-cost technology we fabricated the smartphone-based device that consists in a cover accessory attached to the smartphone and incorporating a light diffuser over the flash to improve the image quality, a mini dark box and a disposable analytical cartridge containing all the reagents necessary for the complete analysis. The biosensor was developed exploiting coupled enzyme reactions for quantifying L-lactate in oral fluid, which is considered a biomarker of poor tissue perfusion, a key element in the management of severe sepsis, septic shock and in sports performance evaluation. The developed method is sensitive, rapid, and it allows detecting L-lactate in oral fluid in the relevant physiological range, with a limit of detection of 0.1mmolL-1. The extreme simplicity of assay execution (no reagents need to be added) and flexibility of fabrication of the device, together with the high assay versatility (any oxidase can be coupled with HRP-based color change reaction) make our approach suitable for the realization of smartphone-based biosensors able to non-invasively detect a large variety of analytes of clinical interest.
authors.affiliation: Department of Chemistry "Giacomo Ciamician" Alma Mater Studiorum, University of Bologna, Bologna, Italy; Interdepartmental Center of Industrial Research (CIRI) - Energy and Environment, Alma Mater Studiorum, University of Bologna, Bologna, Italy.
authors.forename: Donato
authors.initials: D
authors.lastname: Calabria
authors.affiliation: Department of Chemistry "Giacomo Ciamician" Alma Mater Studiorum, University of Bologna, Bologna, Italy; Interdepartmental Center of Industrial Research (CIRI) - Energy and Environment, Alma Mater Studiorum, University of Bologna, Bologna, Italy; Interuniversity Consortium INBB, Rome, Italy.
authors.forename: Cristiana
authors.initials: C
authors.lastname: Caliceti
authors.affiliation: Department of Chemistry "Giacomo Ciamician" Alma Mater Studiorum, University of Bologna, Bologna, Italy.
authors.forename: Martina
authors.initials: M
authors.lastname: Zangheri
authors.affiliation: Department of Chemistry "Giacomo Ciamician" Alma Mater Studiorum, University of Bologna, Bologna, Italy; Interdepartmental Center of Industrial Research (CIRI) - Energy and Environment, Alma Mater Studiorum, University of Bologna, Bologna, Italy; Interuniversity Consortium INBB, Rome, Italy.
authors.forename: Mara
authors.initials: M
authors.lastname: Mirasoli
authors.affiliation: Interuniversity Consortium INBB, Rome, Italy; Department of Medical and Surgical Science - DIMEC, University of Bologna, S.Orsola-Malpighi Hospital, Bologna, Italy.
authors.forename: Patrizia
authors.initials: P
authors.lastname: Simoni
authors.affiliation: Department of Chemistry "Giacomo Ciamician" Alma Mater Studiorum, University of Bologna, Bologna, Italy; Interdepartmental Center of Industrial Research (CIRI) - Energy and Environment, Alma Mater Studiorum, University of Bologna, Bologna, Italy; Interuniversity Consortium INBB, Rome, Italy. Electronic address: aldo.roda@unibo.it.
authors.forename: Aldo
authors.initials: A
authors.lastname: Roda
mesh_terms: D015374:Biosensing Techniques / Q000379:methods*; D001826:Body Fluids / Q000737:chemistry; D006801:Humans; D019344:Lactic Acid / Q000302:isolation & purification*; D010209:Paper; D000068997:Smartphone
chemical_list: D019344:Lactic Acid
keywords: Colorimetric paper-based assay; Enzymatic biosensor; Point-of-care diagnostics; Reagentless; Salivary L-lactate; Smartphone