Immobilization strategies and electrochemical evaluation of porous silicon based cytochrome c electrode

Microsecond All-Optical Modulation by Biofunctionalized Porous Silicon Microcavity

We successfully created a composite photonic structure out of porous silicon (PSi) microcavities doped by the photochromic protein, photoactive yellow protein (PYP). Massive incorporation of the protein molecules into the pores was substantiated by a 30 nm shift of the resonance dip upon functionalization, and light-induced reflectance changes of the device due to the protein photocycle were recorded. Model calculations for the photonic properties of the device were consistent with earlier results on the nonlinear optical properties of the protein, whose degree of incorporation into the PSi structure was also estimated. The successful proof-of-concept results are discussed in light of possible practical applications in the future.

Functionalization of a Fully Integrated Electrophotonic Silicon Circuit for Biotin Sensing

Electrophotonic (EPh) circuits are novel systems where photons and electrons can be controlled simultaneously in the same integrated circuit, attaining the development of innovative sensors for different applications. In this work, we present a complementary metal-oxide-semiconductor (CMOS)-compatible EPh circuit for biotin sensing, in which a silicon-based light source is monolithically integrated. The device is composed of an integrated light source, a waveguide, and a p-n photodiode, which are all fabricated in the same chip. The functionalization of the waveguide's surface was investigated to biotinylate the EPh system for potential biosensing applications. The modified surfaces were characterized by AFM, optical microscopy, and Raman spectroscopy, as well as by photoluminescence measurements. The changes on the waveguide's surface due to functionalization and biotinylation translated into different photocurrent intensities detected in the photodiode, demonstrating the potential uses of the EPh circuit as a biosensor.

Electrochemical and optical investigation of dental pulp stem cell adhesion on modified porous silicon scaffolds

Extensive use of porous silicon (PSi) for tissue engineering is due to its convenient properties as it is both nontoxic and bioresorbable. Moreover, PSi surface modification is an important step to enhance cell adhesion and proliferation. In this work, a combination of optical and electrochemical studies is performed to elaborate a suitable PSi multilayer substrate for cell culture. For this study, we modified PSi surface by silanization and antibody grafting (APTES-anti STRO1), the 12-mer specific peptide to silicon p + type coating and the peptide modified with the antibody recognition sequence. Electrochemical characterization of PSi multilayers is performed to investigate its electrical behavior, determine the optimal measuring conditions and reveal the most stable PSi surfaces. Then, the behavior of dental pulp stem cells (DPSC) was investigated on various modified PSi surfaces. An electrochemical method was applied for the first time monitoring the electrical behavior of stem cell adhesion. The cells electrochemical behavior depends on the nature of the surface coating and the peptide-anti STRO1 improved adhesion and cell spreading onto the PSi surface compared to bare surface and the one coated with the peptide. Fluorescent microscopy revealed that all surface modification methods enhance cell adhesion compared to the bare PSi surface. An increased cell number is observed on APTES-anti STRO1, peptide and peptide-anti STRO1 coated PSi. The peptide-anti STRO1 provided the best cell proliferation results suggesting the improved accessibility of the recognition fragment of the antibody anti-STRO1.

Graphene quantum dots supported by graphene oxide as a sensitive fluorescence nanosensor for cytochrome c detection and intracellular imaging

A new class of Cyt c detection fluorescence sensor based on graphene quantum dots supported by graphene oxide has been facilely developed. The sensor shows a high sensitivity and selectivity for Cyt c detection, and further exhibits favorable intracellular imaging in A549 cells.