Τhe synthesis of a series of novel hybrid block copolypeptides based on poly(ethylene oxide) (PEO), poly(l-histidine) (PHis) and poly(l-cysteine) (PCys) is presented. The synthesis of the terpolymers was achieved through a ring-opening polymerization (ROP) of the corresponding protected N-carboxy anhydrides of Nim-Trityl-l-histidine and S-tert-butyl-l-cysteine, using an end-amine-functionalized poly(ethylene oxide) (mPEO-NH2) as macroinitiator, followed by the deprotection of the polypeptidic blocks. The topology of PCys was either the middle block, the end block or was randomly distributed along the PHis chain. These amphiphilic hybrid copolypeptides assemble in aqueous media to form micellar structures, comprised of an outer hydrophilic corona of PEO chains, and a pH- and redox-responsive hydrophobic layer based on PHis and PCys. Due to the presence of the thiol groups of PCys, a crosslinking process was achieved further stabilizing the nanoparticles (NPs) formed. Dynamic light scattering (DLS), static light scattering (SLS) and transmission electron microscopy (TEM) were utilized to obtain the structure of the NPs. Moreover, the pH and redox responsiveness in the presence of the reductive tripeptide of glutathione (GSH) was investigated at the empty as well as the loaded NPs. The ability of the synthesized polymers to mimic natural proteins was examined by Circular Dichroism (CD), while the study of zeta potential revealed the "stealth" properties of NPs. The anticancer drug doxorubicin (DOX) was efficiently encapsulated in the hydrophobic core of the nanostructures and released under pH and redox conditions that simulate the healthy and cancer tissue environment. It was found that the topology of PCys significantly altered the structure as well as the release profile of the NPs. Finally, in vitro cytotoxicity assay of the DOX-loaded NPs against three different breast cancer cell lines showed that the nanocarriers exhibited similar or slightly better activity as compared to the free drug, rendering these novel NPs very promising materials for drug delivery applications.
Molecular rotors belong to a family of fluorescent compounds characterized as molecular switches, where a fluorescence on/off signal signifies a change in the molecule's microenvironment. Herein, the successful synthesis and detailed study of (E)-2-cyano-3-(p-(dimethylamino)phenyl)-N-(ß-D-glucopyranosyl)acrylamide (RotA), is reported. RotA was found to be a strong inhibitor of rabbit muscle glycogen phosphorylase (RMGPb), that binds at the catalytic site of the enzyme. RotA's interactions with the residues lining the catalytic site of RMGPb were determined by X-ray crystallography. Spectroscopic studies coupled with theoretical calculations proved that RotA is a molecular rotor. When bound in the catalytic channel of RMGPb, it behaved as a light switch, generating a strong fluorescence signal, allowing utilization of RotA as a probe that locates glycogen phosphorylase (GP). RotA, mono-, di- and per-acetylated derivatives, as well as nanoparticles with RotA encapsulated in polyethylene glycol-poly-L-histidine, were used in live cell fluorescence microscopy imaging to test the delivery of RotA through the plasma membrane of HepG2 and A431 cells, with the nanoparticles providing the best results. Once in the intracellular milieu, RotA exhibits remarkable colocalization with GP and significant biological effects, both in cell growth and inhibition of GP.
Enzyme Inhibitors , Glucose , Molecular Probes , Animals , Binding Sites , Crystallography, X-Ray , Enzyme Inhibitors/chemistry , Glucose/analysis , Glycogen Phosphorylase/antagonists & inhibitors , Kinetics , Molecular Probes/chemistry , Oligosaccharides , Rabbits
The synthesis of well-defined polypeptides exhibiting complex macromolecular architectures requires the use of monomers that can be orthogonally deprotected, containing primary amines that will be used as the initiator for the Ring Opening Polymerization (ROP) of N-carboxy anhydrides. The synthesis and characterization of the novel monomer Nε-9-Fluorenylmethoxycarbonyl-l-Lysine N-carboxy anhydride (Nε-Fmoc-l-Lysine NCA), as well as the novel linear Poly(Nε-Fmoc-l-Lys)n homopolypeptide and Poly(l-Lysine)78-block-[Poly(l-Lysine)10-graft-Poly(l-Histidine)15] block-graft copolypeptide, are presented. The synthesis of the graft copolypeptide was conducted via ROP of the Nε-Boc-l-Lysine NCA while using n-hexylamine as the initiator, followed by the polymerization of Nε-Fmoc-l-Lysine NCA. The last block was selectively deprotected under basic conditions, and the resulting ε-amines were used as the initiating species for the ROP of Nim-Trityl-l-Histidine NCA. Finally, the Boc- and Trt- groups were deprotected by TFA. High Vacuum Techniques were applied to achieve the conditions that are required for the synthesis of well-defined polypeptides. The molecular characterization indicated that the polypeptides exhibited high degree of molecular and compositional homogeneity. Finally, Dynamic Light Scattering, ζ-potential, and Circular Dichroism measurements were used in order to investigate the ability of the polypeptide to self-assemble in different conditions. This monomer opens avenues for the synthesis of polypeptides with complex macromolecular architectures that can define the aggregation behavior, and, therefore, can lead to the synthesis of "smart" stimuli-responsive nanocarriers for controlled drug delivery applications.
Cardiovascular diseases (CVDs) are the leading cause of death globally, taking an estimated 17.9 million lives each year, representing one third of global mortality. As existing therapies still have limited success, due to the inability to control the biodistribution of the currently approved drugs, the quality of life of these patients is modest. The advent of nanomedicine has brought new insights in innovative treatment strategies. For this reason, several novel nanotechnologies have been developed for both targeted and prolonged delivery of therapeutics to the cardiovascular system tο minimize side effects. In this regard, nanoparticles made of natural and/or synthetic nanomaterials, like liposomes, polymers or inorganic materials, are emerging alternatives for the encapsulation of already approved drugs to control their delivery in a targeted way. Therefore, nanomedicine has attracted the attention of the scientific community as a potential platform to deliver therapeutics to the injured heart. In this review, we discuss the current types of biomaterials that have been investigated as potential therapeutic interventions for CVDs as they open up a host of possibilities for more targeted and effective therapies, as well as minimally invasive treatments.
The development of multifunctional polymeric materials for biological applications is mainly guided by the goal of achieving the encapsulation of pharmaceutical compounds through a self-assembly process to form nanoconstructs that control the biodistribution of the active compounds, and therefore minimize systemic side effects. Micelles are formed from amphiphilic polymers in a selective solvent. In biological applications, micelles are formed in water, and their cores are loaded with hydrophobic pharmaceutics, where they are solubilized and are usually delivered through the blood compartment. Even though a large number of polymeric materials that form nanocarrier delivery systems has been investigated, a surprisingly small subset of these technologies has demonstrated potentially curative preclinical results, and fewer have progressed towards commercialization. One of the most promising classes of polymeric materials for drug delivery applications is polypeptides, which combine the properties of the conventional polymers with the 3D structure of natural proteins, i.e., α-helices and ß-sheets. In this article, the synthetic pathways followed to develop well-defined polymeric micelles based on polypeptides prepared through ring-opening polymerization (ROP) of N-carboxy anhydrides are reviewed. Among these works, we focus on studies performed on micellar delivery systems to treat cancer. The review is limited to systems presented from 2000â»2017.
