Langmuir and Langmuir–Blodgett Films of Poly[(9,9-dioctylfluorene)-co-(3-hexylthiophene)] for Immobilization of Phytase: Possible Application as a Phytic Acid Sensor

Abstract

In this work, the copolymer poly­[(9,9-dioctylfluorene)-co-(3-hexylthiophene)] was employed as a matrix for immobilizing phytase, aiming at the detection of phytic acid. The copolymer was spread on the air–water interface forming Langmuir monolayers and phytase adsorbed from the aqueous subphase. The interactions between the copolymer and the enzyme components were investigated with surface pressure and surface potential–area isotherms, Brewster angle microscopy, and polarization modulation infrared reflection–absorption spectroscopy (PM-IRRAS). The enzyme could be incorporated in the monolayers from the aqueous subphase, expanding the copolymer films and maintaining its secondary structure. The polymeric films presented a morphological heterogeneous pattern at the air–water interface because of the ability of their chains to fold and entangle, causing inherent defects in the organization as well as unbalanced lateral distribution at the air–water interface because of the formation of aggregates. The interfacial films were transferred to solid supports as Langmuir–Blodgett films and characterized by PM-IRRAS and scanning electronic microscopy, which showed not only the co-transfer of the enzyme but also the maintenance of their heterogeneous morphological pattern. The enzymatic activity of the blended film was analyzed by UV–vis spectroscopy and allowed the estimation of the value of the Michaelis constant (13.08 mM), demonstrating the feasibility of the system to selectively detect phytic acid for biosensing purposes.

The Past and the Future of Langmuir and Langmuir–Blodgett Films

“…Biosensors containing urease, algal polysaccharides, CNT, and DODAB were used to detect urea with capacitance–voltage and constant capacitance measurements . Semiconducting polymers can also be used in flexible matrices providing stable enzyme activity in LB films, e.g., for phytase to detect phytic acid and urease to detect urea. , The cartoon in Figure illustrates the procedure to fabricate urease-containing LB films for detecting urea where the organized nature of the film facilitated analyte diffusion and electron transfer.…”

Nanocomposite Films of Silver Nanoparticles and Conjugated Copolymer in Natural and Nano-Form: Structural and Morphological Studies

“…In turn, the bands at 1360 and 1088 cm −1 are attributed to the C-S-C stretch and asymmetric C-O-C stretch of the EDOT group, respectively. The bands at 890–810 cm −1 are attributed to the symmetric C-O-C stretch of the EDOT group and the out-of-plane C-H angular deformation of the fluorene rings [ 18 , 21 , 22 ]. Therefore, FTIR analysis confirms co-polymer structure formation.…”

Prominent processing techniques to manipulate semiconducting polymer microstructures

“…242 Under similar LB conditions, 3D ordered film microstructures comprising poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV) chains oriented in-plane were fabricated on plastic substrates for sensing purposes. 243 Preparation of polymeric films with sensing properties was further targeted through the use of poly[(9,9-dioctylfluorene)- co -(3-hexylthiophene)] 244 and PANI. 245 In the latter case, Sharma and co-workers produced nanocomposites of PANI titanium oxide (TiO 2 ) comprising tiny TiO 2 particles well dispersed in the PANI-TiO 2 films, by controlling the compression and substrate lifting speeds, while keeping the surface pressure constant.…”