A capillary electrophoresis strategy to sensitively detect dynamic properties of coiled coil polypeptides.

The self-assembly behavior of polypeptides plays an essential role to form biological and functional macromolecules, which have attracted a lot of attention due to their excellent characters. Understanding the polypeptide self-assembly systems and dynamic behaviors is fundamental to improve the potential of biomedical applications. In this work, coiled coil polypeptides PC10 and PC10 P were designed and biosynthesized. PC10 and PC10 P could form nanogels when the concentration of polypeptides was less than 2% (m/v). The dynamic behaviors of PC10 and PC10 P were measured by Förster resonance energy transfer method based on a capillary electrophoresis system. The Förster resonance energy transfer efficiency of this system was 60.4%, and the distance of self-assembled domains in the polypeptides was calculated as 6.14 nm, demonstrating that the exchange behavior occurred between two different polypeptides containing the same coiled coil region.

HIV-related DNA detection through switching on hybridized quenched fluorescent DNA-Ag nanoclusters.

In this paper, DNA containing six cytosines as the formation site for silver nanoclusters (Ag NCs) was adopted as a template for preparing fluorescent DNA-Ag NCs. For the first time, it was found that the fluorescence of DNA-Ag NCs could be quenched after hybridization with their complementary sequence. On the basis of this new phenomenon, we designed a sequence C1 that was completely complementary to human immunodeficiency virus (HIV) DNA, and probe DNA which was partially complementary to C1 for the synthesis of DNA-Ag NCs. The fluorescence of DNA-Ag NCs was quenched after hybridization with C1 and the DNA-Ag NCs/C1 composite was formed, while C1 could be dissociated away from the DNA-Ag NCs by HIV DNA through a strand exchange reaction due to the stronger affinity between HIV DNA and C1, which could switch on the quenched Ag NCs, thus a new "off-on" fluorescence method for HIV DNA detection was developed. In the experiment, the Ag NCs formation site of DNA, the number of base pairs, and the pH and salt concentration of binding buffer were optimized. Under the optimum conditions, the limit of detection for HIV DNA was obtained to be 3.18 nM (3σ/N, n = 7) with the linear range of 15-150 nM for the 150 nM DNA-Ag NCs/C1 probe. Besides, the probe showed excellent specificity to HIV DNA, and even distinguished one nucleotide mismatched HIV DNA.

In vivo tumor active cancer targeting and CT-fluorescence dual-modal imaging with nanoprobe based on gold nanorods and InP/ZnS quantum dots.

In this paper, gold nanorods and InP/ZnS quantum dots were encapsulated together in a silica medium, and the targeting molecular peptide c(RGDfC) was further connected after surface modification with PEG and PEG derivatives to prepare a multifunctional Au@QD@SiO2/PEG-c(RGDfC) probe. Dynamic Light Scattering showed that the probe size was about 215.01 ± 2.72 nm, and its dispersibility was good. In in vitro experiments when the concentration was as high as 200 µg mL-1, the activity of the cells was still 85% due to low toxicity. In vivo experiments showed that the probe had excellent tumor targeting, X-ray computed tomography (CT) imaging and fluorescence imaging capabilities. The experiments revealed that the probe had a long blood circulation time (T1/2 = 7.78 h) in mice. Biochemical analysis, liver enzyme analysis and histomorphological analysis after probe injection showed that the probe had no obvious side effects on the normal functions of the main organs, indicating good biosafety. In vivo imaging experiments showed that 6 d after intravenous injection, the tumor sites of a HeLa tumor-bearing nude mice positive group presented obvious fluorescence and CT signals, indicating that the prepared nanoprobe had good tumor targeting dual-mode imaging capabilities and therefore showed great potential in biomedical imaging applications, especially the diagnosis of cancer.