Poly(D,L-lactide-co-glycolide) dispersions containing pluronics: from particle preparation to temperature-triggered aggregation

Mechanical properties and state of miscibility in poly(racD,L-lactide-co-glycolide)/(L-lactide-co-ε-caprolactone) blends

Polymers based on lactic acid (PLA) are a very promising category of biopolymers. As they are multi-stimuli responsive, can, in many ways, positively interact with the host, stimulating the innate reparative machinery of the human body. Since biopolymers for medical applications are subject to restrictive regulations, blending stands out as an effective method for obtaining tailored properties within a reduced time to market if compared to synthesis. Hence, in this study a set of PDLGA/PLCL blends was obtained by means of thermoplastic techniques and then further characterized. Evaluation techniques include GPC, NMR, DSC, tensile testing and SEM. Although mixtures proved to be immiscible, a full range of tensile properties was achieved. Observation of the surfaces of fracture provided visual evidence of the deformation mechanisms that occurred during the tensile tests which in the end led to failure. Interpretation of the thermal events based on molecular characterization parameters revealed phase separation, crystallization and plasticisation mechanisms that are relevant to any potential applications based on mechanical performance and shape memory behaviour.

Thermoresponsive magnetic colloidal gels via surface-initiated polymerisation from functional microparticles

Novel magnetothermally responsive core–shell microparticles have been synthesized.

Bone Regeneration from PLGA Micro-Nanoparticles

Poly-lactic-co-glycolic acid (PLGA) is one of the most widely used synthetic polymers for development of delivery systems for drugs and therapeutic biomolecules and as component of tissue engineering applications. Its properties and versatility allow it to be a reference polymer in manufacturing of nano- and microparticles to encapsulate and deliver a wide variety of hydrophobic and hydrophilic molecules. It additionally facilitates and extends its use to encapsulate biomolecules such as proteins or nucleic acids that can be released in a controlled way. This review focuses on the use of nano/microparticles of PLGA as a delivery system of one of the most commonly used growth factors in bone tissue engineering, the bone morphogenetic protein 2 (BMP2). Thus, all the needed requirements to reach a controlled delivery of BMP2 using PLGA particles as a main component have been examined. The problems and solutions for the adequate development of this system with a great potential in cell differentiation and proliferation processes under a bone regenerative point of view are discussed.

Solvent selection causes remarkable shifts of the "Ouzo region" for poly(lactide-co-glycolide) nanoparticles prepared by nanoprecipitation

Polymer nanoparticles (NPs) offer versatile novel biological features of interest for drug delivery applications. "Ouzo diagrams" allowed for a systematic manufacture of specified colloidal formulations by the widely used nanoprecipitation process. Surprisingly, despite the well-documented relevance of the applied organic solvent for nanoprecipitation, its effect on the actual status of the "Ouzo region" was so far not studied. Herein, investigations were undertaken to account for the potential impact of the solvent type on the "Ouzo diagrams" for poly(lactide-co-glycolide) (PLGA) and tetrahydrofuran (THF), 1,4-dioxane, acetone and dimethyl sulfoxide (DMSO). The "Ouzo region" shifted considerably to higher polymer fractions upon solvent change (rank order: THF < 1,4-dioxane < acetone < DMSO). Assuming a one-to-one transformation of detached PLGA-bearing solvent droplets (droplet diameter for THF: ∼800 nm, 1,4-dioxane: ∼700 nm, acetone: ∼500 nm and DMSO: ∼300 nm) into non-divisible polymer aggregates upon solvent displacement, facilitated to predict the size of NPs found within the "Ouzo region" (size range: 40-200 nm). In conclusion, application of "Ouzo diagrams" is a valuable tool for drug delivery research and will most-likely replace the "trial-and-error"-approach to identify the operating window for the production of stable colloidal formulations by the nanoprecipitation technique.

Polymeric-gold nanohybrids for combined imaging and cancer therapy

Here, the use of folic acid (FA)-functionalized, doxorubicin (DOXO)/superparamagnetic iron oxide nanoparticles (SPION)-loaded poly(lactic-co-glycolic acid) (PLGA)-Au porous shell nanoparticles (NPs) as potential nanoplatforms is reported for targeted multimodal chemo- and photothermal therapy combined with optical and magnetic resonance imaging in cancer. These polymeric-gold nanohybrids (PGNH) are produced by a seeded-growth method using chitosan as an electrostatic "glue" to attach Au seeds to DOXO/SPION-PLGA NPs. In order to determine their potential as theranostic nanoplatforms, their physicochemical properties, cellular uptake, and photothermal and chemotherapeutic efficiencies are tested in vitro using a human cervical cancer (HeLa) cell line. The present NPs show a near-infrared (NIR)-light-triggered release of cargo molecules under illumination and a great capacity to induce localized cell death in a well-focused region. The functionalization of the PGNH NPs with the targeting ligand FA improves their internalization efficiency and specificity. Furthermore, the possibility to guide the PGNH NPs to cancer cells by an external magnetic field is also proven in vitro, which additionally increases the cellular uptake and therapeutic efficiency.

Poly(lactide-co-glycolide)-laponite-F68 nanocomposite vesicles through a single-step double-emulsion method for the controlled release of doxorubicin

Poly(lactide-co-glycolide) (PLGA)-laponite-F68 nanocomposite (PNC) vesicles were prepared through a technically facile, single-step water/oil/water double-emulsion method using ethyl acetate/water mixture. Vesicles of diameter 100 nm to 1.2 μm and average membrane thickness 30 nm were produced. Encapsulation with chemotherapeutic drug doxorubicin revealed unilamellar nature of the vesicle wall. PNC exhibited exfoliated morphology, enhanced thermal stability over neat PLGA, and a glass transition temperature of 54.29 °C. The zeta potential of -14.1 ± 0.231 for the vesicles revealed that the negatively charged PLGA surface is covered with neutral F68 in the vesicle wall. F68-Assisted formation of water/oil/water double emulsion of PNC in ethyl acetate/water mixture is proposed for the formation of the vesicles. Release characteristics of doxorubicin in phosphate-buffered saline (pH 7.4), cytotoxicity of bare and drug-loaded PNC vesicles with L929 cells, and uptake of doxorubicin with C6 fibroblast glioma cell line were also investigated.