The surface modification of silver nanoparticles by phosphoryl disulfides for improved biocompatibility and intracellular uptake.

In order to enhance the biocompatibility and cell affinity of metal nanoparticles for biosensing and drug delivering applications, we prepared the phospholipid derivatives containing disulfide groups to modify silver nanoparticle surfaces. By adding sodium borohydride to reduce both disulfide bonds of the derivatives and silver ions simultaneously, the generated thiol groups can be reacted with newborn silver atoms immediately to generate nanoclusters. The assemblies consisted of either phosphorylcholine (PC) or phosphorylethanolamine (PE) head groups, which made the silver clusters biocompatibile. Transmission electron microscope (TEM) and optical absorption spectra assisted in modulating reaction conditions, demonstrating that a surfactant/Ag ratio of 0.4 led to the formation of uniform, well-dispersed spherical particles about 3.8 nm in diameter. X-ray photoelectron spectra and infrared spectra also illustrated the elemental and molecular structures of nanoparticles. The insertion of rhodamine dye into the surfactant layer enabled the nanoparticles to be used as a fluorescent probe. In cell culture tests, the nanoparticles were internalized into platelet or fibroblast cells in a short period of incubation without harming the cells.

Surface plasmon resonance biosensor with high anti-fouling ability for the detection of cardiac marker troponin T.

Designing a surface recognition layer with high anti-fouling ability, high affinity, and high specificity is an important issue to produce high sensitivity biosensing transducers. In this study, a self-assembled monolayer (SAM) consisting of a homogeneous mixture of oligo(ethylene glycol) (OEG)-terminated alkanethiolate and mercaptohexadecanoic acid (MHDA) on Au was employed for immobilizing troponin T antibody and applied in detecting cardiac troponin T by using surface plasmon resonance (SPR). The mixed SAM showed no phase segregation and exhibited human serum albumin resistance, particularly with an antibody-immobilized surface. X-ray photoemission spectra revealed that the chemical composition ratio of OEG to the mixed SAM was 69% and the OEG packing density was 82%. The specific binding of troponin T on the designed surface indicated a good linear correlation (R=0.991, P<0.0009) at concentrations lower than 50 µgmL(-1) with the limit of detection of 100 ngmL(-1) using a SPR measuring instrument. It is concluded that the mixed SAM functions as designed since it has high detection capability, high accuracy and reproducibility, as well as shows strong potential to be applied in rapid clinical diagnosis for label-free detection within 2 min.