title: Sol-Gel-Based Titania-Silica Thin Film Overlay for Long Period Fiber Grating-Based Biosensors.
abstract: An evanescent wave optical fiber biosensor based on titania-silica-coated long period grating (LPG) is presented. The chemical overlay, which increases the refractive index (RI) sensitivity of the sensor, consists of a sol-gel-based titania-silica thin film, deposited along the sensing portion of the fiber by means of the dip-coating technique. Changing both the sol viscosity and the withdrawal speed during the dip-coating made it possible to adjust the thickness of the film overlay, which is a crucial parameter for the sensor performance. After the functionalization of the fiber surface using a methacrylic acid/methacrylate copolymer, an antibody/antigen (IgG/anti-IgG) assay was carried out to assess the performance of sol-gel based titania-silica-coated LPGs as biosensors. The analyte concentration was determined from the wavelength shift at the end of the binding process and from the initial binding rate. This is the first time that a sol-gel based titania-silica-coated LPG is proposed as an effective and feasible label-free biosensor. The specificity of the sensor was validated by performing the same model assay after spiking anti-IgG into human serum. With this structured LPG, detection limits of the order of tens of micrograms per liter (10(-11) M) are attained.
authors.affiliation: Institute of Applied Physics "Nello Carrara", CNR-IFAC , Via Madonna del Piano 10, 50019 Sesto Fiorentino, Italy.
authors.forename: Francesco
authors.initials: F
authors.lastname: Chiavaioli
authors.affiliation: Central Glass and Ceramic Research Institute, CSIR-CGCRI , 196 Raja S C Mullick Road, Kolkata 700032, India.
authors.forename: Palas
authors.initials: P
authors.lastname: Biswas
authors.affiliation: Institute of Applied Physics "Nello Carrara", CNR-IFAC , Via Madonna del Piano 10, 50019 Sesto Fiorentino, Italy.
authors.forename: Cosimo
authors.initials: C
authors.lastname: Trono
authors.affiliation: Central Glass and Ceramic Research Institute, CSIR-CGCRI , 196 Raja S C Mullick Road, Kolkata 700032, India.
authors.forename: Sunirmal
authors.initials: S
authors.lastname: Jana
authors.affiliation: Central Glass and Ceramic Research Institute, CSIR-CGCRI , 196 Raja S C Mullick Road, Kolkata 700032, India.
authors.forename: Somnath
authors.initials: S
authors.lastname: Bandyopadhyay
authors.affiliation: Central Glass and Ceramic Research Institute, CSIR-CGCRI , 196 Raja S C Mullick Road, Kolkata 700032, India.
authors.forename: Nandini
authors.initials: N
authors.lastname: Basumallick
authors.affiliation: Institute of Applied Physics "Nello Carrara", CNR-IFAC , Via Madonna del Piano 10, 50019 Sesto Fiorentino, Italy.
authors.forename: Ambra
authors.initials: A
authors.lastname: Giannetti
authors.affiliation: Institute of Applied Physics "Nello Carrara", CNR-IFAC , Via Madonna del Piano 10, 50019 Sesto Fiorentino, Italy.
authors.forename: Sara
authors.initials: S
authors.lastname: Tombelli
authors.affiliation: Central Glass and Ceramic Research Institute, CSIR-CGCRI , 196 Raja S C Mullick Road, Kolkata 700032, India.
authors.forename: Susanta
authors.initials: S
authors.lastname: Bera
authors.affiliation: Central Glass and Ceramic Research Institute, CSIR-CGCRI , 196 Raja S C Mullick Road, Kolkata 700032, India.
authors.forename: Aparajita
authors.initials: A
authors.lastname: Mallick
authors.affiliation: Institute of Applied Physics "Nello Carrara", CNR-IFAC , Via Madonna del Piano 10, 50019 Sesto Fiorentino, Italy.
authors.forename: Francesco
authors.initials: F
authors.lastname: Baldini
mesh_terms: D001681:Biological Assay; D015374:Biosensing Techniques / Q000295:instrumentation* / Q000379:methods*; D006801:Humans; D007136:Immunoglobulins / Q000097:blood; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D058428:Silica Gel / Q000737:chemistry*; D013499:Surface Properties; D014025:Titanium / Q000737:chemistry*
chemical_list: D007136:Immunoglobulins; C009495:titanium dioxide; D058428:Silica Gel; D014025:Titanium