The Role of Substrate Topography and Stiffness on MSC Cells Functions: Key Material Properties for Biomimetic Bone Tissue Engineering

The hypothesis of the present research is that by altering the substrate topography and/or stiffness to make it biomimetic, we can modulate cells behavior. Substrates with similar surface chemistry and varying stiffnesses and topographies were prepared. Bulk PCL and CNTs-reinforced PCL composites were manufactured by solvent casting method and electrospinning and further processed to obtain tunable moduli of elasticity in the range of few MPa. To ensure the same chemical profile for the substrates, a protein coating was added. Substrate topography and properties were investigated. Further on, the feedback of Wharton’s Jelly Umbilical Cord Mesenchymal Stem Cells to substrates characteristics was investigated. Solvent casting scaffolds displayed superior mechanical properties compared to the corresponding electrospun films. However, the biomimetic fibrous texture of the electrospun substrates induced improved feedback of the cells with respect to their viability and proliferation. Cells’ adhesion and differentiation was remarkably pronounced on solvent casting substrates compared to the electrospun substrates. Soft substates improved cells multiplication and migration, while stiff substrates induced differentiation into bone cells. Aspects related to the key factors and the ideal properties of substrates and microenvironments were clarified, aiming towards the deep understanding of the required optimum biomimetic features of biomaterials.

Effect of GNPs on the Piezoresistive, Electrical and Mechanical Properties of PHA and PLA Films

Sustainability has become the primary focus for researchers lately. Biopolymers such as polyhydroxyalkanoate (PHA) and polylactic acid (PLA) are biocompatible and biodegradable. Introducing piezoresistive response in the films produced by PLA and PHA by adding nanoparticles can be interesting. Hence, a study was performed to evaluate the mechanical, electrical and piezoresistive response of films made from PHA and PLA. The films were produced by solvent casting, and they were reinforced with graphene nanoplatelets (GNPs) at different nanoparticle concentrations (from 0.15 to 15 wt.%). Moreover, cellulose nanocrystals (CNC) as reinforcing elements and polyethylene glycol (PEG) as plasticizers were added. After the assessment of the nanoparticle distribution, the films were subjected to tests such as tensile, electrical conductivity and piezoresistive response. The dispersion was found to be good in PLA films and there exist some agglomerations in PHA films. The results suggested that the incorporation of GNPs enhanced the mechanical properties until 0.75 wt.% and they reduced thereon. The addition of 1% CNCs and 20% PEG in 15 wt.% GNPs’ tensile values deteriorated further. The PHA films showed better electrical conductivity compared to the PLA films for the same GNPs wt.%. Gauge factor (GF) values of 6.30 and 4.31 were obtained for PHA and PLA, respectively.

Influence of Solvent and Substrate on Hydrophobicity of PLA Films

The study of the surface properties of materials is key in determining whether the material will be suitable for medical purposes. One of these properties is hydrophobicity, which is important when assessing its behavior against bacterial adhesion. In this work, we have studied the influence of the solvent (chloroform, acetone, and tetrahydrofuran) and the substrate (glass, PTFE, silicone, and Ti6Al4V) on which polylactic acid is deposited in solution to manufacture films by solvent-casting. Thus, it has been found that there are no significant differences in hydrophobicity and surface tension among the solvents evaluated, but there are significant differences with respect to the substrates: PLA films casted on silicone are hydrophobic, while those casted on the rest of the substrates are hydrophilic. This is related to the fact that the silicone interacts with the polymer modifying its spatial arrangement, exposing its methyl groups towards the interface with the air. In this way, it has been shown that, when manufacturing PLA films, it is important to choose the right surface on which to deposit them, depending on their desired function.

Design and Development of Mupirocin Nanofibers as Medicated Textiles for Treatment of Wound Infection in Secondary Burns

The present study assessed the topical potential of nanofibers loaded with Mupirocin (MUP) for the treatment of burns. Nanofibers of MUP were composed of Polyvinyl Pyrrolidone (PVP), Gelatin Type-A, and Ethanol using two methods: Solvent casting and Electrospinning. Nanofibers were characterized for Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), Differential scanning calorimetry (DSC), Thermogravimetric analysis (TGA), Drug Content Studies, in-vitro drug permeation, antibacterial and stability studies. The FT-IR studies showed that the Electrospinning technique had a very good mixing of MUP with the polymer. SEM studies showed that the morphology of electrospinning nanofibers had diameters in the range of 70.41 nm- 406.83 nm. The thermal decomposition studies of optimized Nanofiber (E.S.1) were performed by DSC and TGA study and it was found that the formulation had high stability in high-temperature environments. Permeation studies showed that E.S.1 had the highest percentage amount and controlled release of the drug (90 %) up to 8 has compared to other formulations. Nanofibers prepared through the Electrospinning technique showed better antibacterial activity against Staphylococcus aureus as compared to the Solvent casting nanofibers. This research suggested that MUP loaded nanofibers can be potentially used as a topical drug delivery system for the treatment of burns.

Physical-Mechanical Behavior and Water-Barrier Properties of Biopolymers-Clay Nanocomposites

The preparation and characterization of biodegradable films based on starch-PVA-nanoclay by solvent casting are reported in this study. The films were prepared with a relation of 3:2 of starch:PVA and nanoclay (0.5, 1.0, and 1.5% w/v), and glycerol as plasticizer. The nanoclays before being incorporated in the filmogenic solution of starch-PVA were dispersed in two ways: by magnetic stirring and by sonication. The SEM results suggest that the sonication of nanoclay is necessary to reach a good dispersion along the polymeric matrix. FTIR results of films with 1.0 and 1.5% w/v of sonicated nanoclay suggest a strong interaction of hydrogen bond with the polymeric matrix of starch-PVA. However, the properties of WVP, tensile strength, percentage of elongation at break, and Young’s modulus improved to the film with sonicated nanoclay at 0.5% w/v, while in films with 1.0 and 1.5% w/w these properties were even worse than in film without nanoclay. Nanoclay concentrations higher than 1.0 w/v saturate the polymer matrix, affecting the physicochemical properties. Accordingly, the successful incorporation of nanoclays at 0.5% w/v into the matrix starch-PVA suggests that this film is a good candidate for use as biodegradable packaging.

Chitin Fiber from Mushroom as Reinforcement for Biobased Polymer

This project aimed to study the reinforcement effect of fungal chitin at different loading on chitin/PLA composite. The chitin nanofibers were extracted from three mushroom species (oyster mushroom Pleurotus ostreatus, shiitake mushroom Lentinula edodes, enoki mushroom Flammulina velutipes) and used as a reinforcement element in PLA. The chitin/PLA composite was fabricated using a solvent-casting method followed by the hot-compress molding method. In the solvent-casting method, the chitin nanofibers were dispersed in PLA/chloroform mixture and the mixture was left for solvent evaporation. The solvent-free chitin/PLA thin film was then filled in dog bone mold before proceeded with hot-compress molding at 190°C and 70 bar. The samples with different chitin loading were tested with tensile test to study the mechanical performance of nanocomposite. The chitin/PLA composite from oyster mushroom shows the optimum result (σ= 43 MPa, E= 12 MPa) at 5% chitin loading. The increment of the chitin loading leads to a decrease in both strength and strain. However, for the samples from enoki and shitake mushrooms, the optimum chitin loading is 10% with 55 MPa and 56 MPa tensile strength, respectively. This study suggests the potential of fungal chitin as reinforcement in PLA.

Effect of graphene nanoplatelet addition on the electrical conductivity of poly(hydroxybutyrate-co-hydroxyvalerate) biocomposites

Poly(hydroxybutyrate-co-hydroxyvalerate) (PHBV) is one of the most promising biodegradable polymers used in many applications due to its biodegradability and non-toxicity. However, the usage of PHBV in electronic, biomedical, and biosensor applications has been limited due to its poor electrical properties. This study shows a simple method of producing and enhancing the electrical conductivity of PHBV-based biocomposites by adding graphene nanoplatelet (GNP) as a conductive filler. The biocomposite films were prepared using the solvent casting method, consist of five GNP loading (0-5 wt. %). The prepared PHBV/GNP biocomposites show enhanced electrical conductivity compared to neat PHBV. PHBV/GNP biocomposite with 5 wt. % filler loading exhibits the highest electrical conductivity at 3.83 × 10−3 S/cm. Higher crystalline regions in the PHBV/GNP biocomposites have facilitated the transfer of electrons between PHBV, resulting in the formation of conductive biocomposites, as evident from X-ray diffraction (XRD) characterization.

Development and Evaluation of Trans Buccal Patches based on Natural and Synthetic Polymers Loaded with Rivastigmine using Solvent Casting Technique

Mucoadhesive buccal films of rivastigmine were prepared by the solvent casting technique using HPMC K15M, sodium alginate, glycerine, and Eudragit RL100. Arranged films assessed for weight variation, thickness, % drug substance, % moisture loss, % moisture take-up, folding endurance, in-vitro medicament release, and Fourier transform Infrared spectroscopy (FTIR). The films showed a controlled release (CR) over 8 h. The preparation observed to be a worthy candidate for the development of buccal patches for therapeutic purposes. Drug-polymer compatibility considers FTIR demonstrated no contradiction between the medicament and the polymers. The optimized formulation found F7 indicated drug release 85% at the end of 8 h. Thinking about the correlation coefficient (R2) values got from the kinetic equations, the drug release from the formulations F1-F8 has discovered zero-order release mechanism. It can be concluded that oral buccal patches of rivastigmine, for treatment of Alzheimer’s and Parkinson’s disease, can be formulated. The study suggests that rivastigmine can be conveniently administered orally in the form of buccal patches, with the lesser occurrence of its side effects and improved bioavailability.