No abstract

To characterize the physicochemical and biological stability of nanodevices suitable for biomedical applications, polylactic acid (PLA) nanoparticles (NPs) of 112 ± 6 nm and polyhydroxy butyrate (PHB) of 15 ± 5 nm size were prepared by standardizing the suitable method for each. Morphology of NPs was studied by scanning and transmission electron microscopy and temperature stability by thermogravimetric analysis. Their stability in biological fluids (simulated gastrointestinal and saliva) and tolerance against 0.5 mM NaCl were analyzed. PHB NPs remained stable in all fluids, while after 24 h treatment, the PLA NPs showed the beginning of disintegration with intestinal fluid mimic. In addition to the preparation of polyethylene glycol (PEG) surface-coated NPs, PLA-PEG-PLA triblock copolymer (MW ∼ 7,366 Da) was also chemically synthesized and characterized. Cytotoxicity of all forms of nanoparticles was tested by MTT assay and by annexin pi staining.

Star-shaped polylactide (SSPLA) nanoparticles (NPs) with dipyridamole (DIP) core conjugated with 5-fluorouracil (5FU) and 4-piperidinopiperidine (4PIP) were designed and synthesized to achieve apoptosis by synergistic dose-dependent delivery than using free drugs. In our current investigation, DIP was employed as the initiator in ring-opening polymerization reaction to make SSPLADIP. We then described the synthesis of tailor-made, self-assembled, carboxyl group-substituted fluorescent SSPLADIP conjugated with a secondary amine group of 5FU anticancer drug to form a dual prodrug complex (SSPLADIP5FU). To compare the efficacy of this combination, another anticancer drug 4PIP was also covalently conjugated with a hydroxyl-end terminal by nucleophilic substitution on SSPLADIP to form SSPLADIP4PIP. 4PIP inhibits the topoisomerase enzyme in DNA replication. Synthesized star-shaped drug constructs were characterized by atomic force microscopy, scanning electron microscopy, NMR, fluorescence spectroscopy, gel permeation chromatography, and MALDI-TOF. This is the first report on these drug combinations (DIP−5FU and DIP−4PIP) fabricated on the polylactic acid biopolymer to form NPs of size <150 nm with excellent encapsulation and loading efficiency with time-dependent release in acidic pH (5.4). The release patterns of NPs were accordant with zero-order and Korsmeyer−Peppas models. The glial (G1), pancreatic (MIAPaCa2), colon (DLD1) cancer cells and normal fibroblast cell line (L929 cells) were used to study the NP uptake in lysosomes and nucleus after 48 h by confocal microscopy. The cytotoxicity of SSPLADIP5FUNPs showed an IC 50 of 20 μg/mL in colon cancer cells and remained nontoxic to L929 cells even at 1000 μg/mL. To mimic the colonic environment, we placed free DIP in a simulated colonic fluid with our SSPLADIP5FU NPs. It was observed that our NPs were stable without binding with constituents in the colonic fluid, whereas free DIP bounded with Ca 2+ , protein, and phosphatidylcholine, resulting in quenching of its fluorescence. Apoptosis by tunability ratios of dual drugs was confirmed by fluorescence activated cell sorting and fluorescence resonance energy transfer assay in flow cytometry.