Early stage structural evolution of PLLA porous scaffolds in thermally induced phase separation process and the corresponding biodegradability and biological property

Preparation of nanofibrous poly (L-lactic acid) scaffolds using the thermally induced phase separation technique in dioxane/polyethylene glycol solution

Porous nanofibrous poly (L-lactic acid) (PLLA) scaffolds were fabricated in combination with a thermally induced phase separation technique using a dioxane/polyethylene glycol (PEG) system. The effect of factors such as molecular weight of PEG, aging treatment, aging or gelation temperature, and the ratio of PEG to dioxane were investigated. The results revealed that all scaffolds had high porosity, and had a significant impact on the formation of nanofibrous structures. The decrease in the molecular weight and aging or gelation temperature leads to a thinner and more uniform fibrous structure.

(Bio)manufactured Solutions for Treatment of Bone Defects with Emphasis on US-FDA Regulatory Science Perspective

Bone defects, with second highest demand for surgeries around the globe, may lead to serious health issues and negatively influence patient lives. The advances in biomedical engineering and sciences have led to the development of several creative solutions for bone defect treatment. This review provides a brief summary of bone graft materials, an organized overview of top-down and bottom-up (bio)manufacturing approaches, plus a critical comparison between advantages and limitations of each method. We specifically discuss additive manufacturing techniques and their operation mechanisms in detail. Next, we review the hybrid methods and promising future directions for bone grafting, while giving a comprehensive US-FDA regulatory science perspective, biocompatibility concepts and assessments, and clinical considerations to translate a technology from a research laboratory to the market. The topics covered in this review could potentially fuel future research efforts in bone tissue engineering, and perhaps could also provide novel insights for other tissue engineering applications.

Fabrication and Characterization of Nanofibrous Poly (L-Lactic Acid)/Chitosan-Based Scaffold by Liquid-Liquid Phase Separation Technique for Nerve Tissue Engineering

Fabrication method is one of the essential factors which directly affect on the properties of scaffold. Several techniques have been well established to fabricate nanofibrous scaffolds such as electrospinning. However, preparing a three-dimensional (3-D) interconnected macro-pore scaffold essential for transporting the cell metabolites and nutrients is difficult using the electrospinning method. The main aim of this study was developing a highly porous scaffold by poly (L-lactic acid) (PLLA)/chitosan blend using liquid-liquid phase separation (LLPS) technique, a fast and cost-benefit method, in order to use in nerve tissue engineering. In addition, the effect of different polymeric concentrations on morphology, mechanical properties, hydrophilicity, in vitro degradation rate and pH alteration of the scaffolds were evaluated. Moreover, cell attachment, cell viability and cell proliferation of scaffolds as candidates for nerve tissue engineering was investigated. PLLA/chitosan blend not only had desirable structural properties, porosity, hydrophilicity, mechanical properties, degradation rate and pH alteration but also provided a favorable environment for attachment, viability, and proliferation of human neuroblastoma cells, exhibiting significant potential for nerve tissue engineering applications. However, the polymeric concentration in blend fabrication had influence on both characteristics and cell responses. It concluded that PLLA/chitosan nanofibrous 3-D scaffold fabricated by LLPS method as a suitable candidate for nerve tissue engineering.

Development of a cellulose-based scaffold for sustained delivery of curcumin

Due to the unique properties of cellulose-based materials, they are attractive to be developed in industrial pharmaceutics and biomedical fields. Carboxymethyl-diethyl amino ethyl cellulose scaffold (CM-DEAEC) has been synthesized in the current work as a smart novel derivative of cellulose with a great functionality in drug delivery systems. The scaffolds were well cross-linked with 2% (v/v) epichlorohydrin (ECH), loaded with curcumin (Cur), and then were analyzed by FT-IR, XRD, SEM, and mechanical strength. While developing the ideal delivery platform, curcumin (an important chemotherapeutic agent) was chosen due to its hydrophobicity and poor bioavailability. Thus, we developed a novel scaffold for efficient loading and controlled releasing of curcumin. The swelling ratio of 136%, high curcumin entrapment efficiency (up to 83.7%), sustained in vitro drug release profile, and appropriate degradability in three weeks confirmed significant properties of the CM-DEAEC scaffold. More than 99% antibacterial activity has been observed by the cross-linked curcumin loaded CM-DEAEC scaffolds. Cytotoxicity studies using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay and 4',6-diamidino-2-phenylindole (DAPI) staining showed that cross-inked curcumin loaded CM-DEAEC scaffolds did not show any toxicity using L929 cells. All experiments were compared with CMC scaffolds and better characteristics of the novel scaffold for drug delivery have been confirmed.

Electroactive nanofibers mats based on poly(l-lactic acid)/poly(ortho-ethoxyaniline) blends for biological applications

The combination of scaffolds with desirable topographic characteristics and the use of electrical stimulus consist of a strategy to repair and regenerate tissues. An interesting approach to obtain electroactive scaffolds with the aforementioned features comprises on the use of conducting polymers which can be blended with other biocompatible polymers. In this work, poly(l-lactic acid) (PLLA) and poly(ortho-ethoxyaniline) (POEA) were synthesized and PLLA/POEA mats were prepared for the first time by electrospinning technique. Topographic characterization of PLLA/POEA showed a tunable mean diameter of the nanofibers by changing the electrospinning parameters. The presence of POEA into the blend was confirmed by X-ray photoelectron and Fourier-transform infrared spectroscopy analyses. Differential scanning calorimetry curves of PLLA/POEA exhibited shift positions of T_c and absence of the exothermic peak related to the characteristic isomerization process of POEA at high temperatures. The thermal analysis results indicate a favored miscibility between the polymers which is likely resulted from the strong interaction between polymers functionalities. The homogenous distribution of POEA chains throughout the scaffold rendered redox reversibility property for the mats. Biocompatibility results showed non-cytotoxic features for PLLA/POEA, attesting this novel system as a promising candidate for biological applications.

Aminated EVOH nanofiber membranes for Cr(vi) adsorption from aqueous solution

Ethylene vinyl alcohol (EVOH) nanofiber membranes were prepared by melt-blending extrusion with cellulose acetate butyrate ester (CAB) as the matrix and a high-speed flow deposition process. Then, aminated-EVOH (l-Lys/EVOH, Cy/l-Lys/EVOH and DETA/EVOH) nanofiber membranes were prepared for hexavalent chromium [Cr(vi)] removal by facile chemical modification on the surface of EVOH nanofiber membranes. Scanning electron microscopy (SEM), Fourier transform-infrared (FT-IR) spectroscopy and X-ray photoelectron spectroscopy (XPS) were carried out to test the morphology and structure of aminated-EVOH nanofiber membranes. Adsorption experiments suggested that amination was beneficial to adsorption, and the optimal pH for prepared membranes to Cr removal was 2.0. Adsorption kinetics analysis revealed that the adsorption process was successfully fitted with a Pseudo-second-order model. The Freundlich isothermal model well described the adsorption isotherm data. A thermodynamic study suggested that the adsorption process was endothermic and spontaneous. Aminated-EVOH nanofiber membranes exhibited excellent reusability for Cr removal. The Cr adsorption efficiency of DETA/EVOH nanofiber membranes retained up to 98.73% of the initial adsorption after 6 successive adsorption–desorption cycles.

Aminated-ethylene vinyl alcohol (l-Lys/EVOH, Cy/l-Lys/EVOH and DETA/EVOH) nanofiber membranes were prepared for hexavalent chromium [Cr(vi)] removal by facile chemical modification on the surface of EVOH nanofiber membranes.

FABRICATION AND CHARACTERIZATION OF ELECTROSPUN PLLA/COLLAGEN NANOFIBROUS SCAFFOLD COATED WITH CHITOSAN TO SUSTAIN RELEASE OF ALOE VERA GEL FOR SKIN TISSUE ENGINEERING

Background and aim: Healing of fire-induced wounds has been still a challenge in clinical issues. The aim of this study was to fabricate a nanofibrous poly (L-lactic acid)/collagen (PLLA/COL) scaffold with sustained release of aloe vera (AV) gel using a chitosan (CT)-coated layer for skin tissue engineering applications. Material and methods: Morphology, porosity, tensile strength, hydrophilicity, degradation rate, water vapor permeability and water uptake ratio of the scaffold were characterized. The behaviors of mouse fibroblasts (L929) were evaluated on the scaffold. Results: We observed that although the porosity of the scaffold was decreased, other characteristics were enhanced by coating a CT layer. The scaffold supports attachment, viability and proliferation of mouse fibroblasts. Conclusion: Consequently, the PLLA/COL scaffold coated with CT for sustained release of AV gel can be considered as a desirable scaffold for skin tissue engineering.

Citric acid modification of PLLA nano-fibrous scaffolds to enhance cellular adhesion, proliferation and osteogenic differentiation

Citric acid (CA) was used in a thermally induced phase separation (TIPS) process to improve the surface hydrophilicity and cell affinity of PLLA nano-fibrous scaffolds. The evolution of architecture, structure and physicochemical properties of the scaffold after modification has been investigated. Cell viability, adhesion, proliferation and osteogenic differentiation were characterized to evaluate the cytocompatibility and biological properties of PLLA nano-fibrous scaffolds. Citric acid interacted with PLLA through hydrogen bond association and the introduction of strong polar groups (-COOH) on the PLLA surface improved its hydrophilicity with the contact angle decreasing to a suitable range for cell adhesion and spreading. The cell exhibited extensive spreading on the CA modified PLLA scaffolds with many cellular protrusions interacting with nanofibers. Furthermore, such a modification significantly increased the cell proliferation rate, enhanced the alkaline phosphatase (ALP) activity and bone-related gene expression (ALP, OCN, COL I and Runx2) of mBMSCs along with cell development. The results demonstrate a promising modification method to promote applications of PLLA-based scaffolds.

PLLA nanofibrous paper-based plasmonic substrate with tailored hydrophilicity for focusing SERS detection

We report a new paper-based surface enhanced Raman scattering (SERS) substrate platform contributed by a poly(l-lactic acid) (PLLA) nanofibrous paper adsorbed with plasmonic nanostructures, which can circumvent many challenges of the existing SERS substrates. This PLLA nanofibrous paper has three-dimensional porous structure, extremely clean surface with good hydrophobicity (contact angle is as high as 133.4°), and negligible background interference under Raman laser excitation. Due to the strong electrostatic interaction between PLLA nanofiber and cetyltrimethylammonium bromide (CTAB) molecules, the CTAB-coated gold nanorods (GNRs) are efficiently immobilized onto the fibers. Such a hydrophobic paper substrate with locally hydrophilic SERS-active area can confine analyte molecules and prevent the random spreading of molecules. The confinement leads to focusing effect and the GNRs-PLLA SERS substrate is found to be highly sensitive (0.1 nM Rhodamine 6G and malachite green) and exhibit excellent reproducibility (∼8% relative standard deviation (RSD)) and long-term stability. Furthermore, it is also cost-efficient, with simple fabrication methodology, and demonstrates high sample collection efficiency. All of these benefits ensure that this GNRs-PLLA substrate is a really perfect choice for a variety of SERS applications.

Hierarchical polymeric scaffolds support the growth of MC3T3-E1 cells

Tissue engineering makes use of the principles of biology and engineering to sustain 3D cell growth and promote tissue repair and/or regeneration. In this study, macro/microporous scaffold architectures have been developed using a hybrid solid freeform fabrication/thermally induced phase separation (TIPS) technique. Poly(lactic-co-glycolic acid) (PLGA) dissolved in 1,4-dioxane was used to generate a microporous matrix by the TIPS method. The 3D-bioplotting technique was used to fabricate 3D macroporous constructs made of polyethylene glycol (PEG). Embedding the PEG constructs inside the PLGA solution prior to the TIPS process and subsequent extraction of PEG following solvent removal (1,4-dioaxane) resulted in a macro/microporous structure. These hierarchical scaffolds with a bimodal pore size distribution (<50 and >300 μm) contained orthogonally interconnected macro-channels generated by the extracted PEG. The diameter of the macro-channels was varied by tuning the dispensing parameters of the 3D bioplotter. The in vitro cell culture using murine MC3T3-E1 cell line for 21 days demonstrated that these scaffolds could provide a favorable environment to support cell adhesion and growth.

Effects of processing parameters in thermally induced phase separation technique on porous architecture of scaffolds for bone tissue engineering

Tissue engineering makes use of 3D scaffolds to sustain three-dimensional growth of cells and guide new tissue formation. To meet the multiple requirements for regeneration of biological tissues and organs, a wide range of scaffold fabrication techniques have been developed, aiming to produce porous constructs with the desired pore size range and pore morphology. Among different scaffold fabrication techniques, thermally induced phase separation (TIPS) method has been widely used in recent years because of its potential to produce highly porous scaffolds with interconnected pore morphology. The scaffold architecture can be closely controlled by adjusting the process parameters, including polymer type and concentration, solvent composition, quenching temperature and time, coarsening process, and incorporation of inorganic particles. The objective of this review is to provide information pertaining to the effect of these parameters on the architecture and properties of the scaffolds fabricated by the TIPS technique.

Pectin/carboxymethyl cellulose/microfibrillated cellulose composite scaffolds for tissue engineering

Highly porous three-dimensional scaffolds made of biopolymers are of great interest in tissue engineering applications. A novel scaffold composed of pectin, carboxymethyl cellulose (CMC) and microfibrillated cellulose (MFC) were synthesised using lyophilisation technique. The optimised scaffold with 0.1% MFC, C(0.1%), showed highest compression modulus (~3.987 MPa) and glass transition temperature (~103 °C). The pore size for the control scaffold, C(0%), was in the range of 30-300 μm while it was significantly reduced to 10-250 μm in case of C(0.1%). Using micro computed tomography, the porosity of C(0.1%) was estimated to be 88%. C(0.1%) showed excellent thermal stability and lower degradation rate compared to C(0%). The prepared samples were also characterised using XRD and FTIR. C(0.1%) showed controlled water uptake ability and in vitro degradation in PBS. It exhibited highest cell viability on NIH3T3 fibroblast cell line. These results suggest that these biocompatible composite scaffolds can be used for tissue engineering applications.