Chemically reduced bovine serum albumin (BSA) has been used to modify the surface of water-soluble CdTe quantum dots (QDs). It is demonstrated that the denatured BSA (dBSA) can be conjugated to the surface of CdTe QDs and thereby efficiently improve the chemical stability and the photoluminescence quantum yield (PL QY) of the QDs. It is inferred that a shell-like complex structure CdTe(x)(dBSA)(1-x) will form on the surface of the CdTe "core", resulting in the enhancement of PL intensity and the blue shift of the PL peak. This study of the effects of pH and dBSA concentration on optical properties of dBSA-coated QDs suggests that, at pH 6-9, the solution of dBSA-coated CdTe QDs can keep substantial stability and fluorescent brightness, whereas further increase of pH value leads to a dramatic decrease in PL QY and chemical stability. On the other hand, too high or too low initial dBSA concentration in the QD solution results in a decrease of PL QY for dBSA-coated CdTe QDs. This study provides a new approach of preparing stable water-soluble QDs with high PL QY and controllable luminescent colors for biological labeling applications.

Chemically denatured bovine serum albumin (dBSA)-coated water-soluble cadmium telluride (CdTe) quantum dots (QDs), which can effectively improve the chemical stability and photoluminescence quantum yield of CdTe QDs, were successfully conjugated to an anti-Escherichia coli antibody via a cross-linking reaction. The formation of antibody-conjugated CdTe QDs was confirmed using gel filtration chromatography. The anti-E. coli antibody-conjugated CdTe QDs were then used to detect E. coli O157:H7 and Listeria monocytogenes using fluorescence microscopy. It was shown that, after being conjugated to CdTe QDs, the anti-E. coli antibody still maintained its bioactivity and biorecognition specificity. Succinylated dBSA-coated CdTe QDs also were prepared to conjugate with the anti-E. coli antibody. However, no evidence was found that the succinylation provided a better route for antibody conjugation. Our results demonstrate the potential of bioconjugated CdTe QDs for broad biological applications, such as fluorescence-based pathogen detection and in vitro or in vivo cell imaging.

. (2005). Synthesis of photoacid crosslinkable hydrogels for the fabrication of soft, biomimetic microlens arrays. Retrieved from

The formation and dissociation of beta-lactoglobulin/pectin complexes at various sodium chloride concentrations (CNaCl) have been studied by turbidimetric titration. An increase of CNaCl up to 0.1 M shifts the critical pHphi1, which designates the formation of beta-lactoglobulin/pectin coacervates, to higher pH values, whereas further increase of CNaCl from 0.1 to 0.8 M decreases pHphi1 values. These salt effects can be explained in terms of a salt-enhanced effect at lower salt concentrations or a salt-reduced effect at higher salt concentrations, respectively. On the other hand, the value of pHphi2, which corresponds to the dissociation of beta-lactoglobulin/pectin coacervates, tends to have smaller pH values when CNaCl increases from 0.1 to 0.3 M. No observable pHphi2 values are found at CNaCl higher than 0.3 M. The disappearance of pHphi2 is mainly attributed to the strong self-aggregation capability of beta-lactoglobulin at higher CNaCl. The aggregation of beta-lactoglobulin at high CNaCl is reversible, as suggested by the atomic force microscopy results.

The effect of ionic strength ( I) on the interfacial interactions between pectin and the bovine serum albumin (BSA) surface has been investigated using the quartz crystal microbalance with dissipation monitoring (QCM-D). As I increases from 0.01 to 0.02 M, the frequency shift (Delta F) decreases, whereas the energy dissipation shift (Delta D) changes toward a higher value. Further increase of I from 0.02 to 0.5 M causes both Delta F and Delta D to gradually return to almost zero. The adsorbed mass and thickness of the pectin adlayer estimated from the Voigt model confirm that the adsorption of pectin and the formation of thicker pectin adlayers on a BSA surface are favored by the increase of ionic strength at I = 0.01 approximately 0.02 M. An increase of I above 0.02 M hinders pectin adsorption and causes the formation of a thinner pectin adlayer. The ionic strength-enhanced effect at I values lower than 0.02 M is explained as an increase of ionic strength that can screen the electrostatic repulsion to a larger extent than the electrostatic attraction between pectin and BSA. However, when I is higher than 0.02 M, both electrostatic repulsion and attraction can be significantly screened by the increasing ionic strength, resulting in the ionic strength-reduced effect. On the other hand, the high viscoelasticity of the pectin adlayer revealed by the Voigt model suggests the formation of a network-structured pectin adlayer on the BSA surface, which contains two steps for higher pectin adsorptions at I = 0.0125 approximately 0.1 M by the indication of two slopes in Delta D-Delta F plots.