Tuning Paclitaxel Release Behavior Using Dually-Responsive Nanomicellar Assemblies with Multiple Diselenide/Disulfide Linkages

Background: There are many reasons that lead to the failure of cancer chemotherapy, such as uncontrolled drug release, low drug utilization, and severe side effects. Methods: To overcome these obstacles, we designed two kinds of copolymers with thermal and redox-responsive properties containing multiple diselenide/disulfide bonds polyethylene glycol -alt- diselenodipropionate/disulfhydryldipropionate-b-poly(N-isopropylacrylamide) (abbreviated as PEG-alt-DSeDP-b-PNIPAM and PEG-alt-DSDP-b-PNIPAM) by alternative esterification and following atom transfer radical polymerization. Afterward, these prepared copolymers were mixed with the mass ratio of 8:0, 5:3, 3:5, 0:8 (denoted as S1, S2, S3, and S4, respectively), and self-assembled with paclitaxel (PTX) to obtain PTX-loaded S1, S2, S3, and S4 nanomicellar assemblies, aiming to realize PTX controlled and on-demand release. Results: The chemical structures of these two copolymers were characterized by gel permeation chromatography (GPC), indicating eight diselenide/disulfide linkages and eight PEG units were contained in these copolymers. Moreover, the thermal-responsive property was detected by UV-vis spectroscopy, meanwhile, the redox-responsive property was observed by TEM in the presence of 10 mM glutathione (GSH). We found that 76.90% of PTX was released from S1 nanomicelles within 23 h. In contrast, this percentage decreased to 64.53% for S4 nanomicelles even the incubation time prolonged to 82 h, indicating explosive and slow release behaviors of S1 and S4 nanomicelles, respectively. In addition, gradually decreased fluorescence intensity around the cellular nucleus was occurred from S1 to S4 orderly, which was consistent with cellular uptake and in vivo anti-tumor experiments. Conclusion: This work not only provides a strategy for the controlled and effective release of PTX, but also improves drug bioavailability in cancer treatment.

A general approach to protein folding using thermostable exoshells

In vitro protein folding is a complex process which often results in protein aggregation, low yields and low specific activity. Here we report the use of nanoscale exoshells (tES) to provide complementary nanoenvironments for the folding and release of 12 highly diverse protein substrates ranging from small protein toxins to human albumin, a dimeric protein (alkaline phosphatase), a trimeric ion channel (Omp2a) and the tetrameric tumor suppressor, p53. These proteins represent a unique diversity in size, volume, disulfide linkages, isoelectric point and multi versus monomeric nature of their functional units. Protein encapsulation within tES increased crude soluble yield (3-fold to >100-fold), functional yield (2-fold to >100-fold) and specific activity (3-fold to >100-fold) for all the proteins tested. The average soluble yield was 6.5 mg/100 mg of tES with charge complementation between the tES internal cavity and the protein substrate being the primary determinant of functional folding. Our results confirm the importance of nanoscale electrostatic effects and provide a solution for folding proteins in vitro.

Functional Roles of the von Willebrand Factor Propeptide

The primary polypeptide sequence of von Willebrand factor (VWF) includes an N-terminal 741-amino acid VWF propeptide (VWFpp). In cells expressing VWF, the VWFpp performs two critical functions. In the Golgi, VWFpp mediates the intermolecular disulfide linkages that generate high-molecular-weight VWF multimers. Subsequently, the VWFpp, which is proteolytically cleaved from mature VWF by furin, functions to generate the endothelial storage organelles (Weibel-Palade bodies) in which VWF and a distinct collection of proteins are stored, and from where they undergo regulated secretion from the endothelium. The VWFpp is secreted from endothelial cells as dimers and circulates in plasma with at least some of the dimers associating with a noncovalent manner with the D′D3 domain of mature VWF. The VWFpp has a half-life of 2 to 3 hours in plasma, but to date no extracellular function has been determined for the molecule. Nevertheless, its large size and several biologically interesting structural features (two sets of vicinal cysteines and an RGD sequence) suggest that there may be roles that the VWFpp plays in hemostasis or associated physiological processes such as angiogenesis or wound repair.

Effect of high pressure and setting condition on physico-chemical, structural and functional characteristics of transglutaminase mediated fish gels

Application of High pressure and low temperature setting condition on microbial transglutaminase (MTGase) mediated gelation was studied against conventional cooking in pink perch mince. A high pressure of 250 MPa was given to pink perch mince samples added with and without MTGase enzyme, for a holding time of 12 min and a setting condition of 25 °C for 30 min was given prior and after the treatments. Nine random experiments (T1 to T9) were made against high pressure and cooking and analysed its textural and functional properties. Addition of MTGase and setting conditions had significant effect on the textural properties of the both samples especially in inducing the gel strength. Reduction in total and reactive sulfhydryl groups observed was due to the formation of disulfide linkages, which was found more in T6 to T9. Setting condition had significant effect on protein hydrophobicity in both pressure and heat induced gels. No significant variation in the Ca2+-ATPase enzyme activity was observed among treatments. SEM images revealed more closed and dense fibrous network in samples with enzyme (T6 to T9), due to more protein polymerisation. So MTGase enzyme along with pressure treatment enhanced the conformational stability and produce stronger networks through the formation of non sulfide bonds between proteins and setting reinforced these networks. Hence the synergistic effect of high pressure and MTGase can enhance the textural and functional properties of fish gels, when compared with the conventional cooking.