Isoelectric Bovine Serum Albumin: Robust Blocking Agent for Enhanced Performance in Optical-Fiber Based DNA Sensing

Abstract

Surface blocking is a well-known process for reducing unwanted nonspecific adsorption in sensor fabrication, especially important in the emerging field where DNA/RNA applied. Bovine serum albumin (BSA) is one of the most popular blocking agents with an isoelectric point at pH 4.6. Although it is widely recognized that the adsorption of a blocking agent is strongly affected by its net charge and the maximum adsorption is often observed under its isoelectric form, BSA has long been perfunctorily used for blocking merely in neutral solution, showing poor blocking performances in the optical-fiber evanescent wave (OFEW) based sensing toward DNA target. To meet this challenge, we first put forward the view that isoelectric BSA (iep-BSA) has the best blocking performance and use an OFEW sensor platform to demonstrate this concept. An optical-fiber was covalently modified with amino-DNA, and further coupled with the optical system to detect fluorophore labeled complementary DNA within the evanescent field. A dramatic improvement in the reusability of this DNA modified sensing surface was achieved with 120 stable detection cycles, which ensured accurate quantitative bioassay. As expected, the iep-BSA blocked OFEW system showed enhanced sensing performance toward target DNA with a detection limit of 125 pM. To the best of our knowledge, this is the highest number of regeneration cycles ever reported for a DNA immobilized optical-fiber surface. This study can also serve as a good reference and provide important implications for developing similar DNA-directed surface biosensors.

Targeted Sub-Attomole Cancer Biomarker Detection Based on Phase Singularity 2D Nanomaterial-Enhanced Plasmonic Biosensor

“…Besides biotin molecules, we also detected bovine serum albumin (BSA) molecules, which have relatively high molecular weight (66,463 Da), at different concentration levels based on the giant lateral position shift. In BSA sensing experiments, the lateral position shift shows an abrupt change immediately after the injection of BSA solutions.…”

“…In our experiment, we first immersed the sensing surface with capture antibodies. To block non-specific binding in the sensing surface, we flowed BSA molecules, which is widely used as blocking agent [64][65][66], into the microfluidic chamber in advance to block the unbound sites in the sensing substrate. Then an antigen-containing solution was injected into the microfluidic chamber.…”

Nucleic acid functionalized fiber optic probes for sensing in evanescent wave: optimization and application

“…Before usage in EWFO sensing, all bers were blocked in 2 mg mL À1 isoelectric BSA solution to reduce nonspecic adsorption of non-target DNA. 28 Irrelevant ssDNA (A10) was applied as a class of mixer strand in C6-DNA based ssDNA immobilization. First of all, aldehydefunctionalized silica bers were obtained following the protocol described in 2.2.…”

“…in uids based sensing and further lead to unwanted nonspecic adsorption. 28 We attribute the coarse surface by adopting HF etching solution to the following reason. HF etching proceeds through several sequential steps to remove SiO 2 as silicon tetrauoride (SiF 4 ) and uorosilicic acid (H 2 SiF 6 ).…”

“…However, we found that facile HF etching might induce irreversible structural damage of ber, resulting in a coarse surface with irregular grooves. 28 Considering the small size, exible chain structure and special charge distribution of single strand nucleic acid, great blocking challenges appear when facing the harsh interface conditions. Moreover, researches on improvement of surface induced restricted nucleic acid accessibility and hybridization efficiency have been extensively exploited with respect to gold electrode surface, 29 silicon oxide substrate, 30 at silica slide, 31 untreated distal end of silica ber, 32 and polystyrene microsphere.…”