The clusters of immunogold nanoparticles were fabricated through cross-linking immunogold nanoparticles with glutaraldehyde. A novel strategy for immunoassay signal amplification using the clusters of immunogold nanoparticles on glass slides based on electroless deposition was described. The immunoassay signal amplification through the clusters of immunogold nanoparticles was about three to four times higher than that through single immunogold nanoparticles. The purple attachments were readily discernible on glass slides by naked eye at a concentration of 0.1 pg/mL antigen in PBS solution. The indirect detection of antigen using the clusters of immunogold nanoparticles is an efficient way to improve the detection sensitivity.

It needs appropriately attractive forces to construct multilayer thin films by layer-by-layer (LBL) assembly technique. It is feasible to prepare multilayer thin films on glass slides with negatively charged gold nanoparticles and positively charged lysozyme through the electrostatic LBL assembly technique. The gold nanoparticles/lysozyme multilayer thin films are highly stable; immersion in 0.1 M HCl, NaOH, and surfactant sodium dodecyl sulfate aqueous solutions cannot destroy the films. The highly stable gold nanoparticles/lysozyme multilayer thin films have potential application in long-term antibacterial coating.

A weak polyelectrolyte ultrafiltration membrane based on poly(acrylonitrile and 2-dimethylamino ethyl methacrylate) (PAN-DMAEMA) copolymer was prepared by phase inversion in a wet process. PAN-DMAEMA membrane has the typical asymmetric structure. The results of X-ray photoelectron spectroscopy (XPS) analysis have shown enrichment of PDMAEMA on the membrane surface. Water flux of PAN-DMAEMA ultrafiltration membrane is tunable due to the switch of the stretched and collapsed states of PDMAEMA chains at different pH and NaCl concentration in the feed solutions. The water flux of PAN-DMAEMA membrane cannot reversibly recover its original flux after environmental stimuli; the reason may be that the residual exchanged-ions and ionic pairs disturb the switch of polymer conformation of PDMAEMA in the skin layer of ultrafiltration membrane.

An amphiphilic comb copolymer with polystyrene as hydrophobic parts and poly(ethyl glycol) (PEG) as hydrophilic parts was blended with polyethersulfone (PES) to fabricate high protein-adsorption-resistant ultrafiltration membranes through a phase inversion process. The hydrophilic PEG segments were spontaneously segregated to the membrane surface during immersion precipitation, which was confirmed by the water contact angle measurement and X-ray photoelectron spectroscopy (XPS). The PEG-enriched surface exhibited higher hydrophilicity and the amount of protein adsorption was remarkably decreased from 6.8 to 0.5μg/cm2. Ultrafiltration experiments showed that the antifouling property of the blend membranes was considerably improved with slight change of permeation properties, and the resistance caused by irreversible fouling was remarkably decreased from 2.70×1012 to 0.34×1012 m−1. The superior protein-adsorption-resistance rendered blend membranes more desirable recycling property. The flux recovery ratio was remained as high as 80.4% after three cycles of BSA ultrafiltration.

Poly(acrylonitrile) (PAN)-based zwitterionic membranes were fabricated through phase inversion in a wet process. It was found that bovine serum albumin (BSA) can adsorb on PAN-based zwitterionic membranes in the absent of electrolyte. A new viewpoint based on electrostatic interactions between the charged amino acid residues in BSA and dipole moments of sulfobetaine groups in the zwitterionic polymers in the absent of salt was put forward to explain the adsorption of protein on the zwitterionic membranes. The adsorbed BSA on PAN-based zwitterionic membranes can be released fast and completely from the membranes at higher NaCl concentration. The controlled adsorption and desorption of BSA on PAN-based zwitterionic membranes was achieved through adjusting NaCl concentration in solution.