title: Determination of nitrite in saliva using microfluidic paper-based analytical devices.
abstract: Point-of-care platforms can provide fast responses, decrease the overall cost of the treatment, allow for in-home determinations with or without a trained specialist, and improve the success of the treatment. This is especially true for microfluidic paper-based analytical devices (μPAD), which can enable the development of highly efficient and versatile analytical tools with applications in a variety of biomedical fields. The objective of this work was the development of μPADs to identify and quantify levels of nitrite in saliva, which has been proposed as a potential marker of periodontitis. The devices were fabricated by wax printing and allowed the detection of nitrite by a colorimetric reaction based on a modified version of the Griess reaction. The presented modifications, along with the implementation of a paper-based platform, address many of the common drawbacks (color development, stability, etc.) associated with the Griess reaction and are supported by results related to the design, characterization, and application of the proposed devices. Under the optimized conditions, the proposed devices enable the determination of nitrite in the 10-1000 μmol L(-1) range with a limit of detection of 10 μmol L(-1) and a sensitivity of 47.5 AU [log (μmol L(-1))](-1). In order to demonstrate the potential impact of this technology in the healthcare industry, the devices were applied to the analysis of a series of real samples, covering the relevant clinical range.
authors.affiliation: University of Texas at San Antonio, Department of Chemistry, San Antonio, TX, USA.
authors.forename: Samir A
authors.initials: SA
authors.lastname: Bhakta
authors.affiliation: Instituto de Quimica de São Carlos, Universidade de São Paulo, São Carlos, SP, Brazil; Instituto Nacional de Ciência e Tecnologia de Bioanalítica, Campinas, SP, Brazil.
authors.forename: Rubiane
authors.initials: R
authors.lastname: Borba
authors.affiliation: Faculdade de Odontologia de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, SP, Brazil.
authors.forename: Mario
authors.initials: M
authors.lastname: Taba
authors.affiliation: University of Texas at San Antonio, Department of Chemistry, San Antonio, TX, USA. Electronic address: carlos.garcia@utsa.edu.
authors.forename: Carlos D
authors.initials: CD
authors.lastname: Garcia
authors.affiliation: Instituto de Quimica de São Carlos, Universidade de São Paulo, São Carlos, SP, Brazil; Instituto Nacional de Ciência e Tecnologia de Bioanalítica, Campinas, SP, Brazil. Electronic address: emanuel@iqsc.usp.br.
authors.forename: Emanuel
authors.initials: E
authors.lastname: Carrilho
mesh_terms: D046210:Microfluidic Analytical Techniques / Q000295:instrumentation / Q000379:methods*; D009573:Nitrites / Q000032:analysis*; D010209:Paper; D012463:Saliva / Q000737:chemistry*
chemical_list: D009573:Nitrites
keywords: Griess reagent; Nitrite; Paper-based microfluidic analytical device; Saliva