Multimeric peptide-based PEG nanocarriers with programmable elimination properties

Abstract

In the current study, the design, synthetic feasibility and biochemical characterization of biodegradable peptidic PEG-based nanocarriers is described. The components were selected to influence the body elimination pathway upon nanocarrier biodegradation. Two prototypical nanocarriers were prepared using non-PEGylated and PEGylated peptidic cores [CH 3 CO-(Lys-βAla-βAla) X -Cys-CONH 2 (X= 2, 4)]. A homodimeric nanocarrier with 4 copies of fluorescein-PEG5kDa was synthesized by linking two PEGylated peptidic cores (X=2) using a disulfide bond. A duallabeled heterodimeric nanocarrier with 2 copies of fluorescein-PEG5kDa and 4 copies of Texas Red was also synthesized. Optimum conditions for linking imaging agents, PEG, or a peptidic core to a peptidic core were determined. Significantly higher yields (69% versus 30%) of the PEGylated peptidic core were obtained by using 2 copies of β-alanine as a spacer along with increasing DMSO concentrations, which resulted in reduced steric hindrance. Stoichiometric addition of the components was also demonstrated and found to be important for reducing polydispersity. Nanocarrier biodegradation was evaluated in simulated intracellular and extracellular/blood environments using 3mM and 10μM glutathione in buffer, respectively. The nanocarrier was 9-fold more stable in the extracellular environment. The results suggest selective intracellular degradation of the nanocarrier into components with known body elimination pathways.

Optimal structural design of mannosylated nanocarriers for macrophage targeting

“…Above 30 kDa, PEG conjugates are neither significantly degraded inside cells, nor exocytosed out of the cells and end up accumulating in lysosomes [59-60]. This is a risk similar to a “lysosomal storage disease” [61], which can be prevented by using degradable PEG carriers to facilitate elimination [62]. In this study, the optimized NC does not activate rat peritoneal resting macrophages (Fig.…”

Surface modifications of nanocarriers for effective intracellular delivery of anti-HIV drugs

“…Surface targeting modifiers specific for macrophages include the chemo-attractant peptide, N-formyl-methione-leucine-phenylalanine (fMLF) and mannose. Biodegradation inside the target cells has been conceptually attempted in this type of nanocarrier [66]. Tat cell penetrating peptide has been used as surface modifier to facilitate endosomal escape [39].…”

“…This is particularly important for drugs that are hydrophilic and act in the cytosol or must gain access to the nuclear compartment [66]. …”

“…A novel polymer bioconjugate scaffold based on the use of a peptide-backbone – PEG scaffold (PB-PEG) was recently reported [66]. The PB-PEG nanocarrier is a polymer bioconjugate type nanocarrier that has multiple attachment sites to which drugs or targeting moieties can be linked.…”

“…The multimeric nanocarrier was 9-fold more stable in the extracellular environment. The results suggest selective intracellular degradation of the nanocarrier into components with known body elimination pathways [66]. …”