Peptide drug carrier: studies on incorporation of vasopressin into nano-associates comprising poly(ethylene glycol)-poly(l-aspartic acid) block copolymer

Poly(aspartic acid) in Biomedical Applications: From Polymerization, Modification, Properties, Degradation, and Biocompatibility to Applications

Poly(aspartic acid) (PASP) is an anionic polypeptide that is a highly versatile, biocompatible, and biodegradable polymer that fulfils key requirements for use in a wide variety of biomedical applications. The derivatives of PASP can be readily tailored via the amine-reactive precursor, poly(succinimide) (PSI), which opens up a large window of opportunity for the design and development of novel biomaterials. PASP also has a strong affinity with calcium ions, resulting in complexation, which has been exploited for bone targeting and biomineralization. In addition, recent studies have further verified the biocompatibility and biodegradability of PASP-based polymers, which is attributed to their protein-like structure. In light of growing interest in PASP and its derivatives, this paper presents a comprehensive review on their synthesis, characterization, modification, biodegradation, biocompatibility, and applications in biomedical areas.

Scope of nanotechnology in ovarian cancer therapeutics

This review describes the use of polymer micelle nanotechnology based chemotherapies for ovarian cancer. While various chemotherapeutic agents can be utilized to improve the survival rate of patients with ovarian cancer, their distribution throughout the entire body results in high normal organ toxicity. Polymer micelle nanotechnology aims to improve the therapeutic efficacy of anti-cancer drugs while minimizing the side effects. Herein, different types of polymer micelle technology based nanotherapies such as PLGA, polymerosomes, acid cleavable, thermosensitive, pH sensitive, and cross-linked micelles are introduced and structural differences are explained. Additionally, production methods, stability, sustainability, drug incorporation and drug release profiles of various polymer micelle based nanoformulations are discussed. An important feature of polymer micelle nanotechnology is the small size (10-100 nm) of particles which improves circulation and enables superior accumulation of the therapeutic drugs at the tumor sites. This review provides a comprehensive evaluation of different types of polymer micelles and their implications in ovarian cancer therapeutics.

Enhancement of hydrophilic drug loading and release characteristics through micellization with new carboxymethyldextran-PEG block copolymers of tunable charge density

The micellization of a model cationic drug, diminazene diaceturate (DIM) and a series of new diblock copolymers, carboxymethyldextran-poly(ethylene glycols) (CMD-PEG), were evaluated as a function of the ionic charge density or degree of substitution (DS) of the carboxymethyldextran block and the molar ratio, [+]/[-], of positive charges provided by the drug to negative charges provided by CMD-PEG. Micelles ([+]/[-]=2) incorporated up to 64% (w/w) DIM and ranged in hydrodynamic radius (R(H)) from 36 to 50 nm, depending on the molecular weight and DS of CMD-PEG. The critical association concentration (CAC) was on the order of 15-50mg/L for CMD-PEG of DS>60%, and ca. 100mg/L for CMD-PEG of DS approximately 30%. The micelles were stable upon storage in solution for up to 2 months and after freeze-drying in the presence of trehalose. They remained intact within the 4<pH<11 range and for solutions of pH 5.3, they resisted increases in salinity up to approximately 0.4M NaCl in the case of CMD-PEG of high DS. However, micelles of DIM and a CMD-PEG of low DS (30%) disintegrated in solutions containing more than 0.1M NaCl, setting a minimum value to the DS of copolymers useful in in vivo applications. Sustained in vitro DIM release was observed for micelles of CMD-PEG of high DS ([+]/[-]=2).

Long-circulating poly(ethylene glycol)-poly(D,L-lactide) block copolymer micelles with modulated surface charge

Reactive polymeric micelles consisting of an alpha-acetal-poly(ethylene glycol)-poly(D,L-lactide) block copolymer (acetal-PEG-PDLLA) with a narrow size distribution were prepared in this study to conjugate small peptidyl ligands, tyrosine (Tyr) and tyrosyl-glutamic acid (Tyr-Glu), through reductive amination after converting the alpha-acetal group to an aldehyde group, allowing modulation of the surface charge of the micelles from neutral (Tyr-) to anionic (Tyr-Glu-). Both of these micelles showed a significantly long circulating time in the blood compartment with 25% of injected dose still circulating even at 24 h. Further, an appreciably lowered uptake into the liver and spleen was demonstrated for the anionic Tyr-Glu-conjugated PEG-PDLLA micelle compared with a neutral Tyr-conjugated micelle, suggesting a substantial role of the slight anionic charge on the micelle surface in avoiding non-specific organ uptake. Stability of the micelle form in the blood compartment was directly observed for the Tyr-PEG-PDLLA micelle by a gel filtration assay of a plasma sample collected from the micelle-injected mice at 24 h. These results demonstrated that a surface-modulated PEG-PDLLA micelle with a suitable size and a narrowly distributed nature has promising potential as a long-circulating carrier system with desirable biocompatibility and biofunctionality.