Luis Diaz-Gomez

Biodegradable electrospun nanofibers coated with platelet-rich plasma for cell adhesion and proliferation

Biodegradable electrospun poly(ε-caprolactone) (PCL) scaffolds were coated with platelet-rich plasma (PRP) to improve cell adhesion and proliferation. PRP was obtained from human buffy coat, and tested on human adipose-derived mesenchymal stem cells (MSCs) to confirm cell proliferation and cytocompatibility. Then, PRP was adsorbed on the PCL scaffolds via lyophilization, which resulted in a uniform sponge-like coating of 2.85 (S.D. 0.14) mg/mg. The scaffolds were evaluated regarding mechanical properties (Youngs modulus, tensile stress and tensile strain), sustained release of total protein and growth factors (PDGF-BB, TGF-β1 and VEGF), and hemocompatibility. MSC seeded on the PRP-PCL nanofibers showed an increased adhesion and proliferation compared to pristine PCL fibers. Moreover, the adsorbed PRP enabled angiogenesis features observed as neovascularization in a chicken chorioallantoic membrane (CAM) model. Overall, these results suggest that PRP-PCL scaffolds hold promise for tissue regeneration applications.

Growth factors delivery from hybrid PCL-starch scaffolds processed using supercritical fluid technology.

Synthetic polymeric scaffolds to be used as surrogates of autologous bone grafts should not only have suitable physicochemical and mechanical properties, but also contain bioactive agents such as growth factors (GFs) to facilitate the tissue growth. For this purpose, cost-effective and autologous GFs sources are preferred to avoid some post-surgery complications after implantation, like immunogenicity or disease transmission, and the scaffolds should be processed using methods able to preserve GFs activity. In this work, poly(ɛ-caprolactone) (PCL) scaffolds incorporating GFs were processed using a green foaming process based on supercritical fluid technology. Preparation rich in growth factors (PRGF), a natural and highly available cocktail of GFs obtained from platelet rich plasma (PRP), was used as GF source. PCL:starch:PRGF (85:10:5 weight ratio) porous solid scaffolds were obtained by a supercritical CO2-assisted foaming process at 100 bar and 37 °C with no need of post-processing steps. Bioactivity of GFs after processing and scaffold cytocompatibility were confirmed using mesenchymal stem cells. The performance of starch as GF control release component was shown to be dependent on starch pre-gelification conditions.

Hydrophobically Modified Keratin Vesicles for GSH-Responsive Intracellular Drug Release.

Redox-responsive polymersomes were prepared by self-assembly of a hydrophobically modified keratin and employing a water addition/solvent evaporation method. Polyethylene glycol-40 stearate (PEG40ST) was chosen as hydrophobic block to be coupled to keratin via radical grafting. The amphiphilic polymer exhibited low critical aggregation concentration (CAC; 10 μg/mL), indicating a good thermodynamic stability. The polymeric vesicles loaded both hydrophilic methotrexate and hydrophobic curcumin with high entrapment efficiencies, and showed a GSH-dependent drug release rate. Confocal studies on HeLa cells revealed that the obtained polymersomes were efficiently internalized. Biocompatibility properties of the proposed delivery vehicle were assessed in HET-CAM test and Balb-3T3 mouse fibroblasts. Polymersomes loaded with either methotrexate or curcumin inhibited HeLa and CHO-K1 cancer cells proliferation. Overall, the proposed keratin polymersomes could be efficient nanocarriers for chemotherapeutic agents.

Additive manufacturing of scaffolds with dexamethasone controlled release for enhanced bone regeneration

The adoption of additive manufacturing in tissue engineering and regenerative medicine (TERM) strategies greatly relies on the development of novel 3D printable materials with advanced properties. In this work we have developed a material for bone TERM applications with tunable bioerosion rate and dexamethasone release profile which can be further employed in fused deposition modelling (the most common and accessible 3D printing technology in the market). The developed material consisted of a blend of poly-ϵ-caprolactone (PCL) and poloxamine (Tetronic®) and was processed into a ready-to-use filament form by means of a simplified melt-based methodology, therefore eliminating the utilization of solvents. 3D scaffolds composed of various blend formulations were additively manufactured and analyzed revealing blend ratio-specific degradation rates and dexamethasone release profiles. Furthermore, in vitro culture studies revealed a similar blend ratio-specific trend concerning the osteoinductive activity of the fabricated scaffolds when these were seeded and cultured with human mesenchymal stem cells. The developed material enables to specifically address different regenerative requirements found in various tissue defects. The versatility of such strategy is further increased by the ability of additive manufacturing to accurately fabricate implants matching any given defect geometry.

Biodegradable PCL/fibroin/hydroxyapatite porous scaffolds prepared by supercritical foaming for bone regeneration

Regenerative medicine seeks advanced solutions for bone repair in the form of bioactive synthetic scaffolds by using simple and reproducible processing techniques. In this work, poly-ε-caprolactone (PCL)-based porous scaffolds with improved osteoconductive and osteoinductive properties were processed by supercritical foaming through a careful tuning of components and processing conditions. Composite scaffolds were prepared from various combinations of PCL, silk fibroin and nano-hydroxyapatite (nHA). The green and cost-effective supercritical CO2 foaming method applied rendered solid scaffolds with 67-70% porosity. The incorporation of fibroin and nHA in the scaffolds increased the compressive modulus, cellular adhesion and calcium deposition. The composite scaffolds were tested in vivo in a large-scale calvarial defect model, and bone regeneration was evaluated for up to 14 weeks after implantation. Histomorphometric results showed that all implanted constructs gave rise to the endochondral bone formation and unveiled the synergistic effect of silk fibroin and nHA on the bone repair extent. The information gathered may shed light on the design and processing criteria of bioactive bone scaffolds.

pH/redox dual-sensitive dextran nanogels for enhanced intracellular drug delivery

Graphical abstract Figure. No caption available. HighlightspH/redox dual‐sensitive dextran nanogels.Drug release carriers in cancer chemotherapeutics.pH dependent internalization in cancer cells. ABSTRACT pH/redox dual‐responsive nanogels (DEX‐SS) were prepared by precipitation polymerization of methacrylated dextran (DEXMA), 2‐aminoethylmethacrylate (AEMA) and N,N′‐bis(acryloyl)cystamine (BAC), and then loaded with methotrexate (MTX). Nanogels were spherical and exhibited homogeneous size distribution (460 nm, PDI < 0.30) as observed using dynamic light scattering (DLS) and scanning electron microscopy (SEM). DEX‐SS were sensitive to the variations of pH and redox environment. Nanogels incubated in buffer pH 5.0 containing 10 mM glutathione (GSH) synergistically increased the mean diameter and the PDI to 750 nm and 0.42, respectively. In vitro release experiments were performed at pH 7.4 and 5.0 with and without GSH. The cumulative release of MTX in pH 5.0 medium with 10 mM GSH was 5‐fold higher than that recorded at pH 7.4 without GSH. Fibroblasts and tumor cells were used to tests the effects of blank DEX‐SS and MTX@DEX‐SS nanogels on cell viability. Remarkable influence of pH on nanogels internalization into HeLa cells was evidenced by means of confocal microscopy and flow cytometry.

Low viscosity-PLGA scaffolds by compressed CO2 foaming for growth factor delivery

Foaming technology using supercritical and compressed fluids has emerged as a promising solution in regenerative medicine for manufacturing porous polymeric scaffolds. Polymers of low inherent viscosity are particularly attractive as scaffold components due to their adequate degradation rate and clearance profiles. However, these polymers lead to scaffolds with limited physical integrity if conventional compressed CO2 foaming is used for their processing. To this end, a modified compressed CO2 foaming method was developed for the processing of mixtures of low inherent viscosity poly(lactic-co-glycolic acid) (PLGA, 0.2 dL g−1) and poly(e-caprolactone) (PCL). The compatibility of the method with the incorporation of growth factors and the role of other admixtures (pregelifed starch) in the scaffold were assessed. Scaffolds were obtained in the form of monoliths and characterized in terms of morphology, physicochemical, and viscoelastic properties; biological tests were carried out to evaluate their ability to promote tissue formation. Scaffolds showed good cell attachment and growth. Results showed that the scaffold composition determined the mechanical and biological performance of the construct and influenced the release profile of the incorporated growth factors.

Synthetic scaffolds with full pore interconnectivity for bone regeneration prepared by supercritical foaming using advanced biofunctional plasticizers

Supercritical foaming allows for the solvent-free processing of synthetic scaffolds for bone regeneration. However, the control on the pore interconnectivity and throat pore size with this technique still needs to be improved. The use of plasticizers may help overcome these limitations. Eugenol, a GRAS natural compound extracted from plants, is proposed in this work as an advanced plasticizer with bioactive properties. Eugenol-containing poly(ε-caprolactone) (PCL) scaffolds were obtained by supercritical foaming (20.0 MPa, 45 °C, 17 h) followed by a one or a two-step depressurization profile. The effects of the eugenol content and the depressurization profile on the porous structure of the material and the physicochemical properties of the scaffold were evaluated. The combination of both processing parameters was successful to simultaneously tune the pore interconnectivity and throat sizes to allow mesenchymal stem cells infiltration. Scaffolds with eugenol were cytocompatible, presented antimicrobial activity preventing the attachment of Gram positive (S. aureus, S. epidermidis) bacteria and showed good tissue integration.

Microparticle-embedded fibroin/alginate beads for prolonged local release of simvastatin hydroxyacid to mesenchymal stem cells

In the present work, we propose silk fibroin/alginate (SF/Alg) beads embedding simvastatin-loaded biodegradable microparticles as a versatile platform capable of tuning SVA release and in so doing osteogenic effects. In a first part of the study, microparticles of poly(lactic-co-glycolic) acid incorporating simvastatin either as lactone (SVL) or as hydroxyacid form (SVA) were prepared by spray-drying. While SVA-loaded microparticles released the drug in three days, long-term release of SVA could be obtained from SVL-loaded microparticles. In this latter case, SVL was promptly transformed to the osteogenic active SVA during release. When tested on mesenchymal stem cells, a time- and dose-dependent effect of SVL-loaded microparticles on cell proliferation and alkaline phosphatase (ALP) activity was found. Thereafter, SVL-loaded microparticles were embedded in SF/Alg beads to limit the initial simvastatin burst and to achieve easier implantation as well. Microparticle-embedded beads showed no cytotoxicity while ALP activity increased. If correctly exploited, the developed system may be suitable as osteogenic polymer scaffolds releasing correct amount of the drug locally for long time-frames.

Polymers in Drug Delivery: Fundamentals

Drug delivery has experienced an outstanding advance in the last few decades. Two key elements have contributed in a large extent to such a progress: the better knowledge of the physio/pathological environments through which the drugs have to pass through to reach their targets, and the development of novel excipients that actively participate in the accomplishment of the aimed delivery. In this context polymers occupy an outstanding position due to the versatility of the synthesis routes and the possibility of tuning their features and performances to fulfill the needs of every particular application. Polymers can finely regulate the site and the rate at which the drug is released from the formulation, improve drug solubility, contribute to the stability in the physiological environment, and help the drug to overcome cellular barriers, facilitating the contact with the therapeutic diana. This Chapter reviews the role of polymers on the evolution of drug delivery systems and the current performances they are expected to play in improving the efficiency and safety of the treatments with both old and novel active pharmaceutical ingredients (APIs). An analysis of how polymers themselves are contributing to optimize classical methods of preparing drugs dosage forms and to envision advanced drug nanocarriers is also included. Whenever possible, the information was organized trying to offer structure-property-functionality relationships, with examples of commercially available materials.