Mengyan Wang,Ying Li,Chi Zhang,Gaiping Li,Lina Zou
A sensitive signal-on photoelectrochemical aptasensor for antibiotic determination was constructed based on the energy level matching between ferrocene and CuInS 2 . P-type CuInS 2 microflower was complexed with reduced graphene oxide (CuInS 2 /rGO) to get photocathode current with good photoelectric conversion efficiency and stability. Then, hairpin DNA (HP) was covalently bonded to the electrode surface. A triple helix DNA (THMS) was used as a molecular switch. After the specific recognition between target and THMS in homogeneous solution, ferrocene labeled probe (Fc-T2) was released. Finally, Fc-T2 was captured by the HP, which leaded the obvious increase of photocurrent for the energy level matching between ferrocene and CuInS 2 . The increase of the photocurrent signal was proportional to the concentration of target amoxicillin (AMOX), the linear range was 100 fM-100 nM with detection limit of 19.57 fM. Meanwhile, the method has been successfully applied for milk and lake water samples analysis with satisfactory results.
Adsorbents modified with small molecular ligands have shown great advantages in the downstream purification of antibody, but they still face some challenges caused by single-site adsorption mechanism. Taking the advantage of hydrophobic binding site and sugar chain in Fc region of antibody molecular, a Y-type ligand-modified adsorbent with two-site synergistic adsorption towards antibody was created by integrating 5-aminobenzimidazole and 3-aminophenylboronic acid on the molecular backbone of triazine bonded on the surface of agarose gel. Using dissociation constant and adsorption capacity as indicators, the interaction between immunoglobulin G (IgG) and the adsorbent was probed by comparison with three control adsorbents and by changing pH, salt concentration, and competitive agents in buffer. All the obtained indicators imply a boronate affinity and hydrophobic charge induction synergistic effect imposed on IgG by the benzimidazole and boric acid group in the Y-type ligand, enabling the adsorbent to provide a stronger affinity (Kd = 4.31×10 −6 M), larger adsorption capacity (Qm = 187 mg/g) and more excellent selectivity for IgG over the adsorbents with single-site adsorption mechanism. This is further demonstrated by selectively isolating IgG from protein mixture and serum. Also, pH is confirmed as an important factor for improving the synergistic effect and adsorption selectivity of the adsorbent. Under optimal condition, IgG was successfully separated from human serum and monoclonal antibody (mAb) from cell culture supernatant, with purities of 94.9 % and 97.5 % and recoveries of 94.3 % and 96.8 %, respectively. The results are comparable to those with protein A adsorbent, suggesting a good application potential of the adsorbent in the separation of antibody drugs.
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