A novel protocol for development of DNA electrochemical biosensor based on gold nanoparticles (AuNPs) modified glassy carbon electrode (GCE) was proposed, which was carried out by the self-assembly of AuNPs on the mercaptophenyl film (MPF) via simple electrografting of in situ generated mercaptophenyl diazonium cations. The resulting MPF was covalently immobilized on GCE surface via C–C bond with high stability, which was desirable in fabrication of excellent performance biosensors. Probe DNA was self-assembled on AuNPs through the well-known Au–thiol binding. The recognition of fabricated DNA electrochemical biosensor toward complementary single-stranded DNA was determined by differential pulse voltammetry with the use of Co(phen)33+ as the electrochemical indicator. Taking advantage of amplification effects of AuNPs and stability of MPF, the developed biosensor could detect target DNA with the detection limit of 7.2 × 10−11 M, which also exhibits good selectivity, stability and regeneration ability for DNA detection.

A new and effective strategy was proposed for preparing new organic-inorganic composite biosorbent with spherical silica as supporting core and chitosan(CS)-based hybrid layer as shell based on sol-gel reaction and simple treatment with sodium hydroxide(NaOH). The coating layer was covalently bound on the supporting silica through polysaccharide incorporated sol-gel process starting from CS and inorganic precursor gamma-glycidoxypropyl-trimethoxysiloxane(GPTMS). GPTMS had epoxide groups and cross-linked amine groups of CS to avoid its acidic solubilization. The composite biosorbent had coarse surface due to the wet phase-inversion by treating in NaOH solution. The prepared biosorbent could be used in treating electric plating wastewater.

A novel protocol for the gold nanoparticles (AuNPs) modification on the electrode surface was proposed, which was based on the self-assembly of AuNPs on the mercapto-diazoaminobenzene monolayer modified electrode. The mercapto-diazoaminobenzene monolayer was obtained by covalent immobilization of 4-aminothiophenol (4-ATP) molecules onto another 4-ATP monolayer functionalized gold electrode by diazotization-coupling reaction. The DNA immobilization and hybridization on the AuNPs modified electrode was further investigated. The prepared AuNPs–ATP–diazo-ATP film demonstrated efficient electron transfer ability for the electroactive species toward the electrode surface due to a large conjugated structure of the mercapto-diazoaminobenzene monolayer. The recognition of fabricated electrochemical DNA biosensor toward complementary single-stranded DNA was determined by differential pulse voltammetry with the use of Co(phen)33+ as an electrochemical indicator. A linear detection range for the complementary target DNA was obtained from 3.01×10−10 to 1.32×10−8M with a detection limit of 9.10×10−11M. The fabricated biosensor also possessed good selectivity and could be regenerated easily.

A new and effective strategy was proposed for the preparation of an organic-inorganic composite matrix by using spherical silica as a supporting core and porous chitosan (CS) hybrid layer as shell, based on sol–gel reaction and simple treatment with ammonia solution. After metal ion loading, immobilized metal affinity adsorbent for protein adsorption was obtained. In the prepared composite matrix, the coating layer was covalently bonded on the supporting silica through polysaccharide incorporated sol–gel process starting from CS and an inorganic precursor γ-glycidoxypropyltrimethoxysiloxane (GPTMS). This siloxane possessed an epoxide group to cross-link amine groups of CS. Scanning electron microscopy investigation showed that the wet phase inversion of CS in ammonia solution endowed the coated CS hybrid layer with a porous surface. X-Ray diffraction investigation revealed significant decrease of CS crystallization, indicating the availability of active amine groups. The as-prepared matrix was also characterized using simultaneous thermogravimetry and differential scanning calorimetry. After loading Cu2+ as pseudo-biospecific ligand, new immobilized metal affinity adsorbent was obtained and its protein adsorption performance was evaluated by batch adsorption experiments using bovine serum albumin (BSA) as a simple model protein. The affinity adsorbent showed fast kinetics and high capability for BSA adsorption. The proposed approach and the prepared matrix showed potential as a platform to conduct bioanalysis.

A novel column-based chromatographic protein refolding strategy was developed using dye-ligand affinity chromatography (DLAC) based on macroporous biomaterial. Chitosan–silica (CS–silica) biomaterial with macroporous surface was used as the supporting matrix for the preparation of the DLAC material. The dye-ligand Cibacron Blue F3GA (CBF) was selected as affinity handle and could be covalently immobilized to form dye-ligand affinity adsorbent (CBF–CS–silica) using the reactivity of NH2 on CS–silica biomaterial. After the model protein catalase was denatured with 6mol/L urea, the denaturant could be rapidly removed and catalase could be successfully refolded as facilitated by the adsorption of CBF–CS–silica. The urea denaturation process and the elute condition for the chromatographic refolding were optimized by measuring tryptophan fluorescence and activity of catalase. The refolding performance of the proposed DLAC was compared with dilution refolding. The protein concentration during the proposed chromatographic refolding increased by a factor of 20 without reducing the yield achieved as compared to dilution refolding. The column-based protein refolding strategy based on dye-ligand affinity chromatography with porous biomaterial being matrix possessed potential in chromatographic refolding of protein.

A novel and simple strategy for fabricating of DNA electrochemical biosensor was developed based on covalent coupling of probe NH2–ssDNA (S1) on Au electrode that had been functionalized by diazotization of assembled 4-aminothiophenol (4-ATP) monolayer. The thiol group of 4-ATP allowed the stable assembly of 4-ATP monolayer. The following diazotization reaction was directly performed to prepare functional diazo–ATP film for covalent coupling of probe S1. Remarkably, it was noting that the diazo–ATP provided a surface with high conductibility for electron transfer. The complementary ssDNA was determined by using differential pulse voltammetry. The linear range of the developed biosensor was from 1.57×10−9 to 4.52×10−7M with a detection limit of 3.26×10−10M. The fabricated biosensor possessed good selectivity and could be regenerated. The covalent immobilization of probe S1 by simple diazotization-coupling on self-assembled 4-ATP monolayer could serve as a versatile platform for DNA immobilization and biosensors fabricating.