Quality-by-Design Approach for Biological API Encapsulation into Polymersomes Using "Off-the-Shelf" Materials: a Study on L-Asparaginase.

Polymersomes are versatile nanostructures for protein delivery with hydrophilic core suitable for large biomolecule encapsulation and protective stable corona. Nonetheless, pharmaceutical products based on polymersomes are not available in the market, yet. Here, using commercially available copolymers, we investigated the encapsulation of the active pharmaceutical ingredient (API) L-asparaginase, an enzyme used to treat acute lymphoblastic leukemia, in polymersomes through a quality-by-design (QbD) approach. This allows for streamlining of processes required for improved bioavailability and pharmaceutical activity. Polymersomes were prepared by bottom-up (temperature switch) and top-down (film hydration) methods employing the diblock copolymers poly(ethylene oxide)-poly(lactic acid) (PEG45-PLA69, PEG114-PLA153, and PEG114-PLA180) and the triblock Pluronic® L-121 (poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide), PEG5-PPO68-PEG5). Quality Target Product Profile (QTPP), Critical Quality Attributes (CQAs), Critical Process Parameters (CPPs), and the risk assessment were discussed for the early phase of polymersome development. An Ishikawa diagram was elaborated focusing on analytical methods, raw materials, and processes for polymersome preparation and L-asparaginase encapsulation. PEG-PLA resulted in diluted polymersomes systems. Nonetheless, a much higher yield of Pluronic® L-121 polymersomes of 200 nm were produced by temperature switch, reaching 5% encapsulation efficiency. Based on these results, a risk estimation matrix was created for an initial risk assessment, which can help in the future development of other polymersome systems with biological APIs nanoencapsulated.

Comparative antibacterial activity of silver nanoparticles synthesised by biological and chemical routes with pluronic F68 as a stabilising agent.

The authors report the comparative antibacterial activity of silver nanoparticles synthesised by biological (using Fusarium oxysporum) and chemical routes in the presence and absence of pluronic F68 as a stabilising agent. The production of silver nanoparticles was evidenced by UV-visible spectra, with absorbance at about 420 nm in the case of both biological and chemical synthesis. X-ray diffraction pattern confirmed the presence of face-centred cubic structure (FCC plane). The nanoparticles characterised by transmission and scanning electron microscopy showed spherical silver nanoparticles with size range of 5-40 and 10-70 nm in the case of biologically and chemically synthesised nanoparticles, respectively. Addition of pluronic F68 showed the stabilisation of silver nanoparticles. Antibacterial efficacy of silver nanoparticles demonstrated different inhibitory activity against Escherichia coli, Pseudomonas aeruginosa and Staphylococcus aureus. Overall, biologically synthesised silver nanoparticles showed higher activity as compared with chemically synthesised nanoparticles. Silver nanoparticles synthesised in the presence of pluronic F68 by the chemical route exhibited synergism in antibacterial activity as compared with those synthesised without pluronic F68. On the contrary, biogenic silver nanoparticles without pluronic F68 showed higher antibacterial potential.

Encapsulation of Antioxidant Gallate Derivatives in Biocompatible Poly(ε-caprolactone)-b-Pluronic-b-Poly(ε-caprolactone) Micelles.

Formulation of antioxidant agents is still a challenge that limits their application in the biomedical field. Pentablock copolymers obtained through modification of two common PEO-PPO-PEO copolymers (Pluronic F127 and F68) with poly(ε-carprolactone) (PCL) were evaluated regarding their capability to form nanocarriers suitable for gallic acid, methyl gallate, and ethyl gallate. Applying a dialysis method, PCL/F127/PCL and PCL/F68/PCL self-assembled into spherical micelles in 0.9% NaCl aqueous solution but notably differed in critical micellar concentration (CMC), micelle core hydrophobicity, and micelle size, as evidenced by pyrene fluorescence, transmission electron microscopy, and dynamic light scattering. Cytotoxicity studies showed that the copolymers were safe at concentrations well above the CMC. Transfer of gallic acid and derivatives from aqueous medium to the micelle phase was characterized in terms of distribution constant and free energy of transference, which were shown to be strongly dependent on the hydrophobicity of the gallate derivatives and the length of PCL in the pentablock copolymer. Antioxidant activity of gallates was challenged against DPPH previously loaded in PCL/F127/PCL and PCL/F68/PCL micelles. The more the hydrophobicity of the gallate derivative, the greater the capability to enter in the micelle and to consume free radicals. In vitro release studies of gallic acid, methyl gallate, and ethyl gallate from the pentablock copolymer micelles also evidenced the influence of the hydrophobicity of both the gallate derivative and the micelle core on release rate, recording a variety of release patterns. Overall, PCL/F127/PCL and PCL/F68/PCL appear as suitable nanocarriers of potent antioxidant agents in a wide range of polarities, which may be useful for diverse therapeutic applications.