Formulation of diblock polymeric nanoparticles through nanoprecipitation technique

Comparison of bulk and microfluidics methods for the formulation of poly-lactic-co-glycolic acid (PLGA) nanoparticles modified with cell-penetrating peptides of different architectures

The efficient and reproducible production of nanoparticles using bulk nanoprecipitation methods is still challenging because of low batch to batch reproducibility. Here, we optimize a bulk nanoprecipitation method using design of experiments and translate to a microfluidic device to formulate surface-modified poly-lactic-co-glycolic (PLGA) nanoparticles. Cell-penetrating peptides (CPPs) with a short, long linear or branched architecture were used for the surface modification of PLGA nanoparticles. The microfluidics method was more time efficient than the bulk nanoprecipitation method and allowed the formulation of uniform PLGA nanoparticles with a size of 150 nm, a polydispersity index below 0.150 and with better reproducibility in comparison to the bulk nanoprecipitation method. After surface modification the size of CPP-tagged PLGA nanoparticles increased to 160–180 nm and the surface charge of the CPP-tagged PLGA nanoparticles varied between −24 mV and +3 mV, depending on the architecture and concentration of the conjugated CPP. Covalent attachment of CPPs to the PLGA polymer was confirmed with FTIR by identifying the formation of an amide bond. The conjugation efficiency of CPPs to the polymeric PLGA nanoparticles was between 32 and 80%. The development and design of reproducible nanoformulations with tuneable surface properties is crucial to understand interactions at the nano-bio interface.

Enhanced immunosuppressive effects of 3,5-bis[4(diethoxymethyl)benzylidene]-1-methyl-piperidin-4-one, an α, β-unsaturated carbonyl-based compound as PLGA-b-PEG nanoparticles

Background: 3,5-Bis[4-(diethoxymethyl)benzylidene]-1-methyl-piperidin-4-one (BBP), a novel synthetic curcumin analogue has been revealed to possess strong in vitro and in vivo immunosuppressive effects. Purpose: The aim of present study was to prepare and characterize BBP-encapsulated polylactic-co-glycolic acid-block-polyethylene glycol (PLGA-b-PEG) nanoparticles and to evaluate its in vivo efficacy against innate and adaptive immune responses. Methods: Male BALB/c mice were orally administered with BBP alone and BBP- encapsulated nanoparticles equivalent to 5, 10 and 20 mg/kg of BBP in distilled water for a period of 14 days. The immunomodulatory potential was appraised by determining its effects on non-specific and specific immune parameters. Results: The results showed that BBP was successfully encapsulated in PLGA-b-PEG polymer with 154.3 nm size and high encapsulation efficiency (79%) while providing a sustained release for 48 hours. BBP nanoparticles showed significant enhanced dose-dependent reduction on the migration of neutrophils, Mac-1 expression, phagocytic activity, reactive oxygen species (ROS) production, serum levels of ceruloplasmin and lysozyme, immunoglobulins and myloperoxidase (MPO) plasma levels when compared to unencapsulated BBP. Enhanced dose-dependent inhibition was also observed on lymphocyte proliferation along with the downregulation of effector cells expression and release of cytokines, and reduction in rat paw oedema in BBP nanoparticles treated mice. At higher doses the suppressive effects of the BBP nanoparticles on various cellular and humoral parameters of immune responses were comparable to that of cyclosporine-A at 20 mg/kg. Conclusion: These findings suggest that the immunosuppressive effects of BBP were enhanced as PLGA-b-PEG nanoparticles.

Nanoparticles in thermosensitive gel based composite nanosystem for ocular diseases

The pentablock (PB) copolymers based composite nanosystems were designed to provide a long-term delivery of macromolecules to the back of the eye. A unique arrangement of each block (polyethylene glycol, polylactic acid, and polycaprolactone) with various molecular weights (PB-A and PB-B) was selected for the synthesis of nanoparticles (NPs) and thermosensitive gel (PB-C) by sequential ring-opening bulk copolymerization reaction. PB copolymers were characterized for their molecular weight and purity by ¹H-NMR spectroscopy and crystallinity by PXRD. The macromolecule model drugs [lysozyme (Lyz ~ 14.5 kDa), IgG-Fab (~ 50 kDa), and IgG (~ 150 kDa)] were selected to delineate the effect of molecular weights on in vitro release profile of nanoformulations. Lyz-, Fab-, and IgG-encapsulated NPs were prepared by double emulsion solvent evaporation method. The entrapment efficiency (EE%) and drug loading (DL%) of macromolecules was higher for PB-B copolymers due to its higher molecular weight and hydrophobicity compare to PB-A. The particle size range of NPs was ~ 200-270 nm. In vitro release profiles of Lyz-, Fab-, and IgG-encapsulated in NPs alone and NPs suspended in gel (composite nanosystem) demonstrated a minimal burst release and drug release over a long period. The effect of hydrodynamic diameter of macromolecules and hydrophobicity of PB copolymers was investigated on the release profile of nanosystems. In vitro biocompatibility study showed negligible cytokine (IL-1, IL-6, and TNF-α) release, which confirmed the safety of the PB copolymers. Based on the results, it is anticipated that long-term ocular delivery of macromolecules can be achieved through composite nanosystems.

PLGA nanoparticle encapsulation reduces toxicity while retaining the therapeutic efficacy of EtNBS-PDT in vitro

Photodynamic therapy regimens, which use light-activated molecules known as photosensitizers, are highly selective against many malignancies and can bypass certain challenging therapeutic resistance mechanisms. Photosensitizers such as the small cationic molecule EtNBS (5-ethylamino-9-diethyl-aminobenzo[a]phenothiazinium chloride) have proven potent against cancer cells that reside within acidic and hypoxic tumour microenvironments. At higher doses, however, these photosensitizers induce "dark toxicity" through light-independent mechanisms. In this study, we evaluated the use of nanoparticle encapsulation to overcome this limitation. Interestingly, encapsulation of the compound within poly(lactic-co-glycolic acid) (PLGA) nanoparticles (PLGA-EtNBS) was found to significantly reduce EtNBS dark toxicity while completely retaining the molecule's cytotoxicity in both normoxic and hypoxic conditions. This dual effect can be attributed to the mechanism of release: EtNBS remains encapsulated until external light irradiation, which stimulates an oxygen-independent, radical-mediated process that degrades the PLGA nanoparticles and releases the molecule. As these PLGA-encapsulated EtNBS nanoparticles are capable of penetrating deeply into the hypoxic and acidic cores of 3D spheroid cultures, they may enable the safe and efficacious treatment of otherwise unresponsive tumour regions.