Amphiphilic Glycopolypeptide Star Copolymer-Based Cross-Linked Nanocarriers for Targeted and Dual-Stimuli-Responsive Drug Delivery.

Glycopolypeptide-based nanocarriers are an attractive class of drug delivery vehicles because of the involvement of carbohydrates in the receptor-mediated endocytosis process. To enhance their efficacy toward controlled and programmable drug delivery, we have prepared stable glycopolypeptide-based bioactive dual-stimuli-responsive (redox and enzyme) micelles for delivery of anticancer drugs specifically to the cancer cells. The amphiphilic biocompatible miktoarm star copolymer, which comprises two hydrophobic poly(ε-caprolactone) blocks, a short poly(propargyl glycine) middle block, and a hydrophilic galactose glycopolypeptide block, was designed and synthesized. The star copolymer is initially self-assembled into un-cross-linked (UCL) micelles, and free alkyne groups at the core-shell interface of the UCL micelles, which were cross-linked by bis(azidoethyl) disulfide (BADS) via click chemistry to form interface cross-linked (ICL) micelles. ICL micelles were found to be stable against dilution. BADS imparted redox-responsive properties to the micelles, while PCL rendered them enzyme-degradable. Dual-stimuli-responsive release behavior with Dox as model drug was studied individually as well as synergistically by applying two stimuli in different sequences. The galactose-containing UCL and ICL micelles were shown to be nontoxic. Intracellular Dox release from UCL and ICL micelles was demonstrated in liver cancer cells (HepG2) by time-dependent cellular uptake studies, and controlled release from ICL micelles compared to UCL micelles was observed. The present report opens a new approach toward targeted and programmable drug delivery in tumor tissues via a specifically targeted (receptor-mediated), dual-responsive, and stable cross-linked nanocarrier system.

Superior HIV-1 TAR Binders with Conformationally Constrained R52 Arginine Mimics in the Tat(48-57) Peptide.

We report a 100-fold increase in binding affinity of the Tat(48-57) peptide to HIV-1 transcriptional activator-responsive element (TAR) RNA by replacing Arg52, an essential and critical residue for Tat's specific binding, with (2S,4S)-4-guanidinoproline. The resulting αTat1M peptide is a far superior binder than γTat1M, a peptide containing another conformationally constrained arginine mimic, (2S,4S)-4-amino-N-(3-guanidinopropyl)proline, or even the control Tat peptide (CtrlTat) itself. Our observations are supported by circular dichroism (CD), isothermal titration calorimetry (ITC), gel electrophoresis and UV spectroscopy studies. Molecular dynamics simulations suggest increased interactions between the more compact αTat1M and TAR RNA, relative to CtrlTat. The CD signature of the RNA itself remains largely unchanged upon binding of the peptides. The Tat mimetics further have better cell uptake properties than the control Tat peptide, thus increasing their potential application as specific TAR-binding molecules.

Antibacterial and anti-TB tat-peptidomimetics with improved efficacy and half-life.

Non-natural antimicrobial peptides are ideal as next-generation antibiotics because of their ability to circumvent the problems of drug resistance and in vivo instability. We report novel all-α- and α,γ-mixed Tat peptide analogues as potential antibacterial and anti-TB agents. These peptides have broad spectrum antibacterial activities against Gram-positive (MICs 0.61 ±â€¯0.03 to 1.35 ±â€¯0.21 µM with the peptide γTatM4) and Gram-negative (MICs 0.71 ±â€¯0.005 to 1.26 ±â€¯0.02 µM with γTatM4) bacteria and are also effective against active and dormant forms of Mycobacterium tuberculosis, including strains that are resistant to rifampicin and isoniazid. The introduction of the non-natural amino acids of the study in the Tat peptide analogues results in increased resistance to degradation by proteolysis, significantly increasing their half-life. The peptides appear to inhibit bacteria by a membrane disruption mechanism, and have only a low cytotoxic effect on mammalian cells.

(R-X-R)4 -Motif Peptides Containing Conformationally Constrained Cyclohexane-Derived Spacers: Effect on Cellular Uptake.

Arginine-rich peptides having the (R-X-R)n motif are among the most effective cell-penetrating peptides (CPPs). Herein we report a several-fold increase in the efficacy of such CPPs if the linear flexible spacer (-X-) in the (R-X-R) motif is replaced by constrained cyclic 1,4-substituted-cyclohexane-derived spacers. Internalization of these oligomers in mammalian cell lines was found to be an energy-dependent process. Incorporation of these constrained, non-proteinogenic amino acid spacers in the CPPs is shown to enhance their proteolytic stability.