Spectroscopic studies and thermal properties of PCL/PMMA biopolymer blend

Grafting of Lactic Acid and ε-Caprolactone onto Alpha-Cellulose and Sugarcane Bagasse Cellulose: Evaluation of Mechanical Properties in Polylactic Acid Composites

In this paper, we present the synthesis of composite materials comprised of α-cellulose and sugarcane bagasse cellulose fibers grafted with lactic acid and ε-caprolactone. These fibers were incorporated as reinforcements into a PLA matrix by extrusion, producing composite materials with improved mechanical properties. The grafting of lactic acid and ε-caprolactone onto the fibers was confirmed by FTIR spectroscopy, demonstrating the chemical modification of the fibers. The morphology of the fibers and composites was analyzed through scanning electron microscopy (SEM), showing that the fibers are encapsulated within the polymeric matrix. This suggests good PLA-fiber interaction for the 90 PLA/10 α-Cel, 90 PLA/10 LAC-g-α-Cel, and 90 PLA/10 ε-CL-g-α-Cel composite materials. The obtained composite materials were tested under tensile loading. Incorporating 10 wt% of LAC-g-FBA-Cel and α-Cel-g-FBA-Cel grafted fibers into the PLA matrix improved the tensile modulus by 28% and 12%, respectively, compared with PLA. The maximum tensile strength values obtained were for composite materials with 10 wt% PLA/α-Cel, LAC-g-α-Cel, and FBA-Cel with 23, 27, and 37% concerning PLA. DSC thermal studies showed a reduction in the glass transition temperature in the composites with grafted fibers. The results suggest better interfacial adhesion between the PLA matrix and both grafted and non-grafted α-cellulose fibers, which contributes to the observed improvements in the mechanical and thermal properties of the composite materials. The results demonstrate that the composites can be produced through extrusion. Once the optimal concentration has been determined, α-cellulose or sugarcane bagasse grafted with lactic acid and ε-caprolactone can be incorporated into the PLA matrix, exhibiting adjustable properties.

Development of Versatile, thermally stable, flexible, UV-resistant and antibacterial polyvinyl alcohol-Nanodiamonds composite for efficient food packaging

This research paper reports an enhancement of thermal, optical, mechanical and antibacterial activities of the Polyvinyl alcohol-Nanodiamonds (PVA-NDs) composite required for the food packaging industry. The synthesis of composites was done by the wet processing method. The large surface area of NDs facilitated the robust interaction between the hydroxyl group and macromolecular chains of PVA to enhance the hydrogen bonding of PVA with NDs rather than PVA molecules. Thus, a reduction in PVA diffraction peak intensity was reported. NDs improved the thermal stability by preventing the out-diffusion of volatile decomposition products of PVA. The results also revealed an enhancement in tensile strength (∼60 MPa) and ductility (∼180 %). PVA-NDs composite efficiently blocked the UVC (100 %), most of the part of the UVB (∼85 % above 300 nm), and UVA (∼58 %). Furthermore, enhanced antibacterial activities were reported for PVA-NDs composite against E. coli and S. aureus. NDs accumulated around the bacterial cells prevented essential cellular functions and led to death. Hence, this composite could be a promising candidate for safe, thermally stable, strong, flexible, transparent, UV- resistant antibacterial food packaging material.

Entropically Toughened Robust Biodegradable Polymer Blends and Composites for Bone Tissue Engineering

Biodegradable polymers and composites are promising candidates for biomedical implants in tissue engineering. However, state-of-the-art composite scaffolds suffer from a strength-toughness dilemma due to poor interfacial adhesion and filler dispersion. In this work, we propose a facile and scalable strategy to fabricate strong and tough biocomposite scaffolds through interfacial toughening. The immiscible biopolymer matrix is compatible by the direct incorporation of a third polymer. Densely entangled polymer chains lead to massive crazes and global shear yields under tension. Weak chemical interaction and high-shear melt processing create nanoscale dispersion of nanofillers within the matrix. The resultant ternary blends and composites exhibit an 11-fold increase in toughness without compromising stiffness and strength. At 70% porosity, three-dimensional (3D)-printed composite scaffolds demonstrate high compressive properties comparable to those of cancellous bones. In vitro cell culture on the scaffolds demonstrates not only good cell viability but also effective osteogenic differentiation of human mesenchymal stem cells. Our findings present a widely applicable strategy to develop high-performance biocomposite materials for tissue regeneration.

NOVEL HIGH-STRENGTH POLYESTER COMPOSITE SCAFFOLDS FOR BONE REGENERATION

Repair of critical sized bone defects, particularly in load-bearing areas, is a major clinical problem that requires surgical intervention and implantation of biological or engineered grafts. For load-bearing sites, it is essential to use engineered grafts that have both sufficient mechanical strength and appropriate pore properties to support bone repair and tissue regeneration. Unfortunately, the mechanical properties of such grafts are often compromised due to the creation of pores required to facilitate tissue ingrowth following implantation. To overcome the limitations associated with porous scaffolds and their reduced mechanical strength, we have developed a methodology for creating a solid structure that retains its bulk mechanical properties while also evolving into a porous structure in a biological environment through degradation and erosion. In this study, we utilized polyesters that have been approved by the FDA, including poly (lactic acid) (PLA), poly(glycolic acid) (PGA), their copolymer PLGA (PLGA, with a ratio of 85:15 and 50:50 of PLA:PGA), and poly(caprolactone) (PCL). These polymers and their ceramic composites with tricalcium phosphate (TCP) were compression molded into solid forms, which exhibited mechanical properties with compressive modulus as high as 2745 ± 364 MPa within the range of human trabecular bone and in the lower range of human cortical bone. The use of fast-degrading PLGA (50:50) and PGA as porogens allowed the formation of pores within the solid structures due to their degradation, and the TCP acts as a buffering agent to neutralize their acidic degradation byproducts. These scaffolds facilitated the growth of new blood vessels and tissue ingrowth in a subcutaneous implantation model. In addition, in a rat critical-sized mandibular bone defects these scaffolds supported bone growth with 70% of new bone volume fraction. Furthermore, the extent of bone regeneration was found to be higher for the scaffolds with bone morphogenic proteins (BMP2), indicating their suitability for bone repair and regeneration.

Oral empagliflozin-loaded tri-layer core-sheath fibers fabricated using tri-axial electrospinning: Enhanced in vitro and in vivo antidiabetic performance

Empagliflozin (EM) was successfully loaded in polycaprolactone/poly (L-lactic acid)/polymethyl methacrylate (PCL/PLA/PMMA) fibers. In the rat β-cell line (BRIN-BD11), the insulin expression ratio of pancreatic β-cells was stimulated at high and low glucose by culturing with tri-layer EM-loaded fiber (EMF) for 48 h. The expression ratios of glucokinase and GLUT-2 proteins increased after EMF treatment. According to the in vitro drug release test, 97% of all drug contained in fibers was released in a controlled manner for 24 h. The pharmacokinetic test revealed that the bioavailability was improved ∼4.8-fold with EMF treatment compared to EM-powder and blood glucose level was effectively controlled for 24 h with EMF. Oral administration of EMF exhibited a better sustainable anti-diabetic activity even in the half-dosage than EM-powder in streptozotocin/nicotinamide-induced T2DM rats. The levels of GLP-1, PPAR-γ, and insulin were increased while the levels of SGLT-2 and TNF-α were decreased with EMF treatment. Also, EMF recovered the histopathological changes in the liver, pancreas, and kidney in T2DM rats and protected pancreatic β-cells. Consequently, EMF is suggested as an unprecedented and promotive treatment approach for T2DM with a higher bioavailability and better antidiabetic effect compared to conventional dosage forms.

Elastomeric Trilayer Substrates with Native-like Mechanical Properties for Heart Valve Leaflet Tissue Engineering

Heart valve leaflets have a complex trilayered structure with layer-specific orientations, anisotropic tensile properties, and elastomeric characteristics that are difficult to mimic collectively. Previously, trilayer leaflet substrates intended for heart valve tissue engineering were developed with nonelastomeric biomaterials that cannot deliver native-like mechanical properties. In this study, by electrospinning polycaprolactone (PCL) polymer and poly(l-lactide-co-ε-caprolactone) (PLCL) copolymer, we created elastomeric trilayer PCL/PLCL leaflet substrates with native-like tensile, flexural, and anisotropic properties and compared them with trilayer PCL leaflet substrates (as control) to find their effectiveness in heart valve leaflet tissue engineering. These substrates were seeded with porcine valvular interstitial cells (PVICs) and cultured for 1 month in static conditions to produce cell-cultured constructs. The PCL/PLCL substrates had lower crystallinity and hydrophobicity but higher anisotropy and flexibility than PCL leaflet substrates. These attributes contributed to more significant cell proliferation, infiltration, extracellular matrix production, and superior gene expression in the PCL/PLCL cell-cultured constructs than in the PCL cell-cultured constructs. Further, the PCL/PLCL constructs showed better resistance to calcification than PCL constructs. Trilayer PCL/PLCL leaflet substrates with native-like mechanical and flexural properties could significantly improve heart valve tissue engineering.

New Method Based on the Direct Analysis in Real Time Coupled with Time-of-Flight Mass Spectrometry to Investigate the Thermal Depolymerization of Poly(methyl methacrylate)

In this work, the isothermal decomposition of poly(methyl methacrylate) synthesized in bulk by the radical route of methyl methacrylate in the presence of azobisisobutyronitrile as the initiator was carried out and monitored for the first time with the DART-Tof-MS technique at different temperatures. Nuclear magnetic resonance (NMR) analysis revealed a predominantly atactic microstructure, and size-exclusion chromatography (SEC) analysis indicated a number average molecular weight of 3 × 10⁵ g·mol^-1 and a polydispersity index of 2.47 for this polymer. Non-isothermal decomposition of this polymer carried out with thermogravimetry analysis (TGA) showed that the weight loss process occurs in two steps. The first one starts at approximately 224 °C and the second at 320 °C. The isothermal decomposition of this polymer carried out and monitored with the DART-Tof-MS method revealed only one stage of weight loss in this process, which begins at approximately 250 °C, not far from that of the second step observed in the case of the non-isothermal process conducted with the TGA method. The results obtained with the MS part of this technique revealed that the isothermal decomposition of this polymer regenerates a significant part of methyl methacrylate monomer, which increases with temperature. This process involves radical chain reactions leading to homolytic chain scissions and leading to the formation of secondary and tertiary alkyl radicals, mainly regenerating methyl methacrylate monomer through an unzipping rearrangement. Although they are in the minority, other fragments, such as the isomers of 2-methyl carboxyl, 4-methyl, penta-2,4-diene and dimethyl carbate, are also among the products detected. At 200 °C, no trace of monomer was observed, which coincides with the first step of the weight loss observed in the TGA. These compounds are different to those reported by other researchers using TGA coupled with mass spectrometry in which methyl isobutyrate, traces of methyl pyruvate and 2,3-butanonedione were detected.

3D-Printed Piezoelectric Porous Bioactive Scaffolds and Clinical Ultrasonic Stimulation Can Help in Enhanced Bone Regeneration

This paper presents a comprehensive effort to develop and analyze first-of-its-kind design-specific and bioactive piezoelectric scaffolds for treating orthopedic defects. The study has three major highlights. First, this is one of the first studies that utilize extrusion-based 3D printing to develop design-specific macroporous piezoelectric scaffolds for treating bone defects. The scaffolds with controlled pore size and architecture were synthesized based on unique composite formulations containing polycaprolactone (PCL) and micron-sized barium titanate (BaTiO3) particles. Second, the bioactive PCL-BaTiO3 piezoelectric composite formulations were explicitly developed in the form of uniform diameter filaments, which served as feedstock material for the fused filament fabrication (FFF)-based 3D printing. A combined method comprising solvent casting and extrusion (melt-blending) was designed and deemed suitable to develop the high-quality PCL-BaTiO3 bioactive composite filaments for 3D printing. Third, clinical ultrasonic stimulation (US) was used to stimulate the piezoelectric effect, i.e., create stress on the PCL-BaTiO3 scaffolds to generate electrical fields. Subsequently, we analyzed the impact of scaffold-generated piezoelectric stimulation on MC3T3 pre-osteoblast behavior. Our results confirmed that FFF could form high-resolution, macroporous piezoelectric scaffolds, and the poled PCL-BaTiO3 composites resulted in the d33 coefficient in the range of 1.2-2.6 pC/N, which is proven suitable for osteogenesis. In vitro results revealed that the scaffolds with a mean pore size of 320 µm resulted in the highest pre-osteoblast growth kinetics. While 1 Hz US resulted in enhanced pre-osteoblast adhesion, proliferation, and spreading, 3 Hz US benefited osteoblast differentiation by upregulating important osteogenic markers. This study proves that 3D-printed bioactive piezoelectric scaffolds coupled with US are promising to expedite bone regeneration in orthopedic defects.

Heat-Stimuli Shape Memory Effect of Poly (ε-Caprolactone)-Cellulose Acetate Composite Tubular Scaffolds

Small-diameter artery disease is the most common clinical occurrence, necessitating the development of small-diameter artificial blood vessels. In this study, seven types of poly(-caprolactone)-cellulose acetate (PCL-CA) composite nanofiber membranes were prepared with different proportions of PCL and CA. The adhesion and growth of Mc3t3-e1 cells were considered to confirm the in vitro cytocompatibility of PCL-CA membranes. A smooth stainless-steel mandrel with a diameter of 4 mm was used to roll up the prepared nanofiber membranes to produce the tubular scaffold with 50 °C hot water. The tubular scaffolds were subjected to axial and circumferential tensile tests. The mechanical performance of the PCL-CA tubular scaffold could be improved by increasing the layers. In addition, the burst pressure (BP) of the tubular scaffolds was increased with the layers, and the BPs of six-layer (2380 ± 36.8 mmHg) and eight-layer (3720 ± 80.5 mmHg) tubular scaffolds were much higher than that of the human saphenous vein (2000 mmHg). The compression shape memory performances of the PCL-CA tubular scaffold with different layers were also investigated to simulate and analyze the contraction and expansion of tubular scaffolds. The experimental results showed that the compression strain of the tubular scaffold in the diameter direction reached 35%, and the ultimate shape recovery rate reached 87%. However, the shape fixity rate and shape recovery rate increased, demonstrating that the optimum number of layers can improve the compression shape memory performance of the tubular scaffold. The results of this study, including comprehensive morphological and mechanical properties and cytocompatibility, indicated the potential applicability of PCL-CA tubular scaffolds as tissue engineering grafts.

Uniaxial and Coaxial Nanofibers PCL/Alginate or PCL/Gelatine Transport and Release Tamoxifen and Curcumin Affecting the Viability of MCF7 Cell Line

Breast cancer is the second cause of cancer death in women worldwide. The search for therapeutic and preventive alternatives has increased in recent years. One synthetic drug for patients with hormone receptor-positive tumours is tamoxifen citrate (TMX). Curcumin (Cur) is a natural compound that is being tested. Both were coupled with nanoscale-controlled and sustained release systems to increase the effectiveness of the treatment and reduce adverse effects. We produced a controlled release system based on uniaxial and coaxial polymeric nanofibers of polycaprolactone (PCL), alginate (Alg) and gelatine (Gel) for the transport and release of TMX and Cur, as a new alternative to breast cancer treatment. Nanofibers combining PCL-Alg and PCL-Gel were fabricated by the electrospinning technique and physicochemically characterised by thermal analysis, absorption spectroscopy in the infrared region and X-ray diffraction. Morphology and size were studied by scanning electron microscopy. Additionally, the release profile of TMX and Cur was obtained by UV-Vis spectroscopy. Additionally, the cytotoxic effect on breast cancer cell line MCF7 and peripheral-blood mononuclear cells (PBMCs) from a healthy donor were evaluated by a Resazurin reduction assay. These assays showed that PCL-TMX nanofiber was highly toxic to both cell types, while PCL-Cur was less toxic.

Enhancement of PCL/PLA Electrospun Nanocomposite Fibers Comprising Silver Nanoparticles Encapsulated with Thymus Vulgaris L. Molecules for Antibacterial and Anticancer Activities

Silver nanoparticles (AgNPs) have been recognized for their outstanding antibacterial activities, which are required for antibacterial coating materials in therapeutic applications. A bacterial-resistant electrospun nanofibrous mat made of polycaprolactone (PCL) in combination with polylactide acid (PLA) containing silver nanoparticles encapsulated with Thymus vulgaris L. (thyme) extract (eAgNPs) was fabricated in order to assess the potential of applicability in biomedical applications such as cancer treatment, wound healing, or surgical sutures. In the current study, PCL and PLA used as the basis polymers were blended with biosynthesized eAgNPs, pure AgNPs, and thyme extract (TE) to observe the effects of additives in terms of antibacterial and anticancer activity and morphologic, thermal, mechanical, biocompatibility, and biodegradability properties. The biological characteristics of fabricated electrospun nanofibrous mats were evaluated in vitro. Physicochemical characteristics of the nanofibrous mats were examined by UV-vis spectrophotometry, scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), energy dispersive X-ray (EDX), Fourier-transform infrared spectroscopy (FTIR), mechanical tensile testing, X-ray diffraction (XRD), thermogravimetric examination (TGA), and water contact angles (WCAs). The results showed that a biodegradable nanofiber scaffold with a mean fiber diameter of 280 nm is morphologically homogeneous and highly hydrophobic, has higher tensile strength than PCL/PLA nanocomposite fiber, and is resistant to Escherichia coli and Staphylococcus aureus. The cytotoxic and anticancer properties of nanomaterials were defined using L929 and SK-MEL-30 cells. The developed material inhibited cell proliferation and led to apoptosis of cell lines. It can be suggested that the use of Thymus vulgaris L. extract-encapsulated silver nanoparticle-doped PCL/PLA nanofibers produced by the electrospinning method has the potential for cancer therapy in skin tumor cell lines.

Chitosan-coated pore wall polycaprolactone three-dimensional porous scaffolds fabricated by porogen leaching method for bone tissue engineering: a comparative study on blending technique to fabricate scaffolds

One of the significant challenges in the fabrication of scaffolds for tissue engineering lies in the direct interaction of bioactive agents with cells in the scaffolds matrix, which curbs the effectiveness of bioactive agents resulting in diminished cell recognition and attachment ability of the scaffolds. Here, three-dimensional porous scaffolds were fabricated using polycaprolactone (PCL) and chitosan, by two approaches, i.e., blending and surface coating to compare their overall effectiveness. Blended scaffolds (Chi-PCL) were compared with the scaffolds fabricated using surface coating technique, where chitosan was coated on the pore wall of PCL scaffolds (C-PCL). The C-PCL exhibited a collective improvement in bioactivities of the stem cell on the scaffold, because of the cell compatible environment provided by the presence of chitosan over the scaffolds interface. The C-PCL showed the enhanced cell attachment and proliferation behavior of the scaffolds along with two-fold increase in hemolysis compatibility compared to Chi-PCL. Furthermore, the compression strength in C-PCL increased by 24.52% and 8.62% increase in total percentage porosity compared to Chi-PCL was attained. Along with this, all the bone markers showed significant upregulation in C-PCL scaffolds, which supported the surface coating technique over the conventional methods, even though the pore size of C-PCL was compromised by 19.98% compared with Chi-PCL.

Development of Waste Polystyrene-Based Copper Oxide/Reduced Graphene Oxide Composites and Their Mechanical, Electrical and Thermal Properties

The current study reports the effect of different wt. ratios of copper oxide nanoparticle (CuO-NPs) and reduced graphene oxide (rGO) as fillers on mechanical, electrical, and thermal properties of waste polystyrene (WPS) matrix. Firstly, thin sheets of WPS-rGO-CuO composites were prepared through solution casting method with different ratios, i.e., 2, 8, 10, 15 and 20 wt.% of CuO-NPs and rGO in WPS matrix. The synthesized composite sheets were characterized by Fourier transform infrared spectroscopy (FTIR), energy dispersive X-ray (EDX), X-ray diffraction (XRD) analysis, scanning electron microscopy (SEM) and thermal gravimetric analysis (TGA). The electrical conductance and mechanical strength of the prepared composites were determined by using LCR meter and universal testing machine (UTM). These properties were dependent on the concentrations of CuO-NPs and rGO. Results display that the addition of both fillers, i.e., rGO and CuO-NPs, collectively led to remarkable increase in the mechanical properties of the composite. The incorporation of rGO-CuO: 15% WPS sample, i.e., WPS-rGO-CuO: 15%, has shown high mechanical strength with tensile strength of 25.282 MPa and Young modulus of 1951.0 MPa, respectively. Similarly, the electrical conductance of the same composite is also enhanced from 6.7 × 10-14 to 4 × 10-7 S/m in contrast to WPS at 2.0 × 106 Hz. The fabricated composites exhibited high thermal stability through TGA analysis in terms of 3.52% and 6.055% wt. loss at 250 °C as compared to WPS.

Hemolytic, Biocompatible, and Functional Effect of Cellularized Polycaprolactone-Hydrolyzed Collagen Electrospun Membranes for Possible Application as Vascular Implants

In search of bioactive vascular prostheses that exhibit greater biocompatibility through the combination of natural and synthetic polymers, tissue engineering from a biomimetic perspective has proposed the development of three-dimensional structures as therapeutic strategies in the field of cardiovascular medicine. Techniques such as electrospinning allow obtaining of scaffolds that emulate the microarchitecture of the extracellular matrix of native vessels; thus, this study aimed to evaluate the biological influence of microarchitecture on polycaprolactone (PCL) and hydrolyzed collagen (H-Col) electrospun scaffolds, which have a homogeneous (microscale) or heterogeneous (micro-nanoscale) fibrillar structure. The hemolytic, biocompatible, and functional effect of the scaffolds in interaction with an in vitro fibroblast model was determined, in view of its potential use for vascular implants. Scaffolds were characterized by scanning electron microscopy and atomic force microscopy, Fourier transform infrared spectroscopy, wettability, static permeability, tensile test, and degradation. In addition, direct and indirect 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assays were used to identify the cell viability of fibroblasts, fluorescence assays were performed to establish morphological changes of the cell nuclei, and the hemolytic effect of the scaffolds was calculated. Results showed that ethanol-treated biocompositescaffolds exhibited mass losses lower than 6.65% and slow wettability and absorption, resulting from an increase in secondary structures that contribute to the crystalline phase of H-Col. The scaffolds demonstrated stable degradation in saline during the incubation period because of the availability of soluble structures in aqueous media, and the inclusion of H-Col increased the elastic properties of the scaffold. As regards hemocompatibility, the scaffolds had hemolysis levels lower than 1%; moreover, in terms of biocompatible characteristics, scaffolds exhibited good adhesion, proliferation, and cell viability and insignificant changes in the circularity of the cell nuclei. However, scaffolds with homogeneous fibers showed cell agglomerates after 48 h of interaction. By contrast, permeability decreased as the incubation period progressed, because of the cellularization of the three-dimensional structure. In conclusion, multiscale scaffolds could exhibit a suitable behavior as a bioactive small-diameter vascular implant.

Bismuth subsalicylate incorporated in polycaprolactone-gelatin membranes by electrospinning to prevent bacterial colonization

Periodontitis is a chronic, multifactorial, inflammatory disease characterized by the progressive destruction of the periodontal tissues. Guided tissue regeneration (GTR), involving the use of barrier membranes, is one of the most successful clinical procedures for periodontal therapy. Nevertheless, rapid degradation of the membranes and membrane-related infections are considered two of the major reasons for GTR clinical failure. Recently, integration of non-antibiotic, antimicrobial materials to the membranes has emerged as a novel strategy to face the bacterial infection challenge, without increasing bacterial resistance. In this sense, bismuth subsalicylate (BSS) is a non-antibiotic, metal-based antimicrobial agent effective against different bacterial strains, that has been long safely used in medical treatments. Thus, the aim of the present work was to fabricate fibrillar, non-rapidly bioresorbable, antibacterial GTR membranes composed of polycaprolactone (PCL), gelatin (Gel), and BSS as the antibacterial agent. PCL-G-BSS membranes with three different BSS concentrations (2 wt./v%, 4 wt./v%, and 6 wt./v%) were developed by electrospinning and their morphology, composition, water wettability, mechanical properties, Bi release and degradation rate were characterized. The Cytotoxicity of the membranes was studiedin vitrousing human osteoblasts (hFOB) and gingival fibroblasts (HGF-1), and their antibacterial activity was tested againstAggregatibacter actinomycetemcomitans, Escherichia coli, Porphyromonas gingivalisandStaphylococcus aureus.The membranes obtained exhibited adequate mechanical properties for clinical application, and appropriate degradation rates for allowing periodontal defects regeneration. The hFOB and HGF-1 cells displayed adequate viability when in contact with the lixiviated products from the membranes, and, in general, displayed antibacterial activity against the four bacteria strains tested. Thus, the PCL-G-BSS membranes showed to be appropriate as potential barrier membranes for periodontal GTR treatments.

PCL/Andiroba Oil (Carapa guianensis Aubl.) Hybrid Film for Wound Healing Applications

Developing a biomimetic material to wound care is an emerging need for the healing process. Poly (ε-caprolactone) (PCL) is a polymer with the necessary dressing's requirements often used in medicine. Their surface, physic-chemical and biological properties can be modified by adding bioactive compounds, such as andiroba seed oil (Carapa guianensis). This Amazonian natural plant has medicinal and pharmacological properties. For this purpose, PCL polymeric films incorporated with andiroba oil were investigated. The synthesis of hybrids materials was carried out in the solvent casting method. Thermal properties were evaluated using thermogravimetric analysis (TGA/DTGA) and differential scanning calorimetry (DSC). The solvent type on the surface and hydrophilicity of samples was studied using a scanning electron microscope (SEM). Additionally, contact angle measurements, functional groups analysis, fluid absorption capacity, and cell viability were performed. The results demonstrated the influences of andiroba oil under the morphology and thermal properties of the polymeric matrix; the hydrophilicity of the hybrid film obtained by acetic acid was reduced by 13%; the porosity decreased as the concentration of oil increased, but its higher thermal stability. The L929 cell line's proliferation was observed in all materials, and it presented nontoxic nature. It was demonstrated the ability of PCL hybrid film as a matrix for cell growth. Then, the materials were proved potential candidates for biomedical applications.

Three-Dimensional Printing of Curcumin-Loaded Biodegradable and Flexible Scaffold for Intracranial Therapy of Glioblastoma Multiforme

A novel drug delivery system preventing Glioblastoma multiforme (GBM) recurrence after resection surgery is imperatively required to overcome the mechanical limitation of the current local drug delivery system and to offer personalised treatment options for GBM patients. In this study, 3D printed biodegradable flexible porous scaffolds were developed via Fused Deposition Modelling (FDM) three-dimensional (3D) printing technology for the local delivery of curcumin. The flexible porous scaffolds were 3D printed with various geometries containing 1, 3, 5, and 7% (w/w) of curcumin, respectively, using curcumin-loaded polycaprolactone (PCL) filaments. The scaffolds were characterised by a series of characterisation studies and in vitro studies were also performed including drug release study, scaffold degradation study, and cytotoxicity study. The curcumin-loaded PCL scaffolds displayed versatile spatiotemporal characteristics. The polymeric scaffolds obtained great mechanical flexibility with a low tensile modulus of less than 2 MPa, and 4 to 7-fold ultimate tensile strain, which can avoid the mechanical mismatch problem of commercially available GLIADEL wafer with a further improvement in surgical margin coverage. In vitro release profiles have demonstrated the sustained release patterns of curcumin with adjustable release amounts and durations up to 77 h. MTT study has demonstrated the great cytotoxic effect of curcumin-loaded scaffolds against the U87 human GBM cell line. Therefore, 3D printed curcumin-loaded scaffold has great promise to provide better GBM treatment options with its mechanical flexibility and customisability to match individual needs, preventing post-surgery GBM recurrence and eventually prolonging the life expectancy of GBM patients.

Smart Electrospun Hybrid Nanofibers Functionalized with Ligand-Free Titanium Nitride (TiN) Nanoparticles for Tissue Engineering

Herein, we report the fabrication and characterization of novel polycaprolactone (PCL)-based nanofibers functionalized with bare (ligand-free) titanium nitride (TiN) nanoparticles (NPs) for tissue engineering applications. Nanofibers were prepared by a newly developed protocol based on the electrospinning of PCL solutions together with TiN NPs synthesized by femtosecond laser ablation in acetone. The generated hybrid nanofibers were characterised using spectroscopy, microscopy, and thermal analysis techniques. As shown by scanning electron microscopy measurements, the fabricated electrospun nanofibers had uniform morphology, while their diameter varied between 0.403 ± 0.230 µm and 1.1 ± 0.15 µm by optimising electrospinning solutions and parameters. Thermal analysis measurements demonstrated that the inclusion of TiN NPs in nanofibers led to slight variation in mass degradation initiation and phase change behaviour (T_m). In vitro viability tests using the incubation of 3T3 fibroblast cells in a nanofiber-based matrix did not reveal any adverse effects, confirming the biocompatibility of hybrid nanofiber structures. The generated hybrid nanofibers functionalized with plasmonic TiN NPs are promising for the development of smart scaffold for tissue engineering platforms and open up new avenues for theranostic applications.

3D-Printed Drug Delivery Systems: The Effects of Drug Incorporation Methods on Their Release and Antibacterial Efficiency

Additive manufacturing technologies have been widely used in the medical field. More specifically, fused filament fabrication (FFF) 3D-printing technology has been thoroughly investigated to produce drug delivery systems. Recently, few researchers have explored the possibility of directly 3D printing such systems without the need for producing a filament which is usually the feedstock material for the printer. This was possible via direct feeding of a mixture consisting of the carrier polymer and the required drug. However, as this direct feeding approach shows limited homogenizing abilities, it is vital to investigate the effect of the pre-mixing step on the quality of the 3D printed products. Our study investigates the two commonly used mixing approaches-solvent casting and powder mixing. For this purpose, polycaprolactone (PCL) was used as the main polymer under investigation and gentamicin sulfate (GS) was selected as a reference. The produced systems' efficacy was investigated for bacterial and biofilm prevention. Our data show that the solvent casting approach offers improved drug distribution within the polymeric matrix, as was observed from micro-computed topography and scanning electron microscopy visualization. Moreover, this approach shows a higher drug release rate and thus improved antibacterial efficacy. However, there were no differences among the tested approaches in terms of thermal and mechanical properties.

Nanocomposite scaffolds composed of Apacite (apatite-calcite) nanostructures, poly (ε-caprolactone) and poly (2-hydroxyethylmethacrylate): The effect of nanostructures on physico-mechanical properties and osteogenic differentiation of human bone marrow mesenchymal stem cells in vitro

Nanocomposite scaffolds were fabricated from poly (ε-caprolactone) (PCL), Poly (2-hydroxyethylmethacrylate) (PHEMA), and Apacite (Apatite-calcite) nanostructures (15 and 25 wt%). The nanoscale structure, physical and chemical properties, mechanical properties, hydrophilic behavior, degradability and osteogenic properties of the fabricated scaffolds were evaluated. The results showed that the mechanical strength, degradation, wetting ability, and mechanical strength of PCL-PHEMA scaffolds significantly increases upon inclusion of Apacite nanoparticles up to 25 wt%. Accordingly, the best mechanical values (E ~ 7.109 MPa and σ ~ 0.414 MPa) and highest degradability (32% within 96 h) were recorded for PCL-PHEMA scaffolds containing 25 wt% of Apacite. Furthermore, highest porosity and roughness were observed in the PCL-PHEMA/25% Apacite as a result of the Apacite nanoparticles inclusion. There was no cytotoxicity recorded for the fabricated scaffolds based on the results obtained from MTT assay and acridine orange staining. Alkaline phosphatase activity, calcium content quantification, Van Kossa staining, FESEM and real time PCR tests confirmed the biomineralization, and the differentiation potential of the nanocomposite scaffolds. Overall, the 3D structure, optimum porosity and balanced dissolution rate of PCL-PHEMA/25% Apacite providing a balanced microenvironment resulted in improved cell adhesion, cell behavior, and replication, as well as osteogenic induction of human bone-marrow-derived mesenchymal stem cells (hBM-MSCs).

Preparation of Nanoscale Semi-IPNs with an Interconnected Microporous Structure via Cationic Polymerization of Bio-Based Tung Oil in a Homogeneous Solution of Poly(ε-caprolactone)

Nanoscale semi-interpenetrating polymer networks of bio-based poly(ε-caprolactone) (PCL) and polymerized tung oil have been prepared via in situ cationic polymerization and compatibilization in a homogeneous solution. This novel blending technique produced a nanoscale morphology of poly(ε-caprolactone) with average particle sizes as small as 100 nm dispersed in a cross-linked tung oil matrix for 20 and 30 wt % PCL blend compositions. In addition, the exothermic cationic polymerization of tung oil in the presence of the PCL homogeneous solution created a microporous morphology with open three-dimensional interconnected cluster structures. The porous morphology was found to be composition-dependent (the pore size and interconnectivity decreased with increasing PCL content in the blend). The values of the cross-link density and storage modulus in the glassy state for fully cured samples increased significantly and reached a maximum for the 20 wt % PCL blend. This simple, versatile, low-cost strategy for preparing nanoscale and interconnected three-dimensional cluster structures with a microporous morphology and desired properties should be widely applicable for new polymer systems.

Preparation of Poloxamer188-b-PCL and Study on in vitro Radioprotection Activity of Curcumin-Loaded Nanoparticles

A novel polymer of poloxamer188-b-PCL was synthesized via a ring-opening polymerization. Fourier transform infrared spectroscopy (FTIR), Raman, and ¹H nuclear magnetic resonance (¹H NMR) spectra were used to study the structures of obtained poloxamer188-b-PCL. The thermo-stability of poloxamer188 -b-PCL was carried out with a thermal gravimetric analyzer (TGA), and cytotoxicity was obtained using the CCK8 method. Cargo-free and curcumin (CUR)-loaded poloxamer188-b-PCL NPs were fabricated via the solvent evaporation method. The morphology, particle size distribution, and stability of cargo-free NPs were studied with a scanning electron microscope (SEM) and laser particle analyzer. The in vitro radioprotection activity of CUR-loaded NPs was performed. FTIR, Raman, and ¹H NMR spectra confirmed that poloxamer188-b-PCL was obtained. TGA curves suggested poloxamer188-b-PCL had better thermo-stability than original poloxamer188. Cell tests suggested that the cargo-free NPs had no cytotoxicity. SEM image showed that the cargo-free NPs were spherical with a diameter of 100 nm. Free radical scavenging experiments proved that CUR-loaded NPs had better antioxidant activity than CUR solutions. CUR-loaded NPs could be detected in all tissues, including liver, kidneys and lung. In summary, this work demonstrated a feasibility of developing an injective formulation of CUR and provided a protection agent in caner radiotherapy.

Synthesis and characterization of poly(methyl methacrylate) co-doped with Tb(tmhd)3 - Rhodamine B for luminescent optical fiber applications

Currently, there is a growing interest in the development of multi-colored materials based on the combination of two or more systems (organic or inorganic) as a strategy to take advantage of their combined physical or chemical properties. These multi-colored materials have found potential applications as sensors, amplifiers, and optical fibers. In this work, the physical characteristics of poly(methyl methacrylate) (PMMA) doped with Terbium(III)-tris-(2,2,6,6-tetramethyl-3,5-heptanedionate) (Tb(tmhd)₃) at 1.57-1.58 mmol and Rhodamine B (RhB) at different concentrations were analyzed. The emission obtained from these samples (multichromophoric samples) varied as function of RhB concentration due to an efficient energy transfer process (33-65%). The role of PMMA as inert matrix that assists in the recombination process was confirmed by FTIR and Raman spectra analysis. Moreover, an improvement in thermal resistance of the materials was observed due to the presence of the dopants during the polymerization process.

Antibacterial composite membranes of polycaprolactone/gelatin loaded with zinc oxide nanoparticles for guided tissue regeneration

The bacterial colonization of absorbable membranes used for guided tissue regeneration (GTR), as well as their rapid degradation that can cause their rupture, are considered the major reasons for clinical failure. To address this, composite membranes of polycaprolactone (PCL) and gelatin (Gel) loaded with zinc oxide nanoparticles (ZnO-NPs; 1, 3 and 6 wt% relative to PCL content) were fabricated by electrospinning. To fabricate homogeneous fibrillar membranes, acetic acid was used as a sole common solvent to enhance the miscibility of PCL and Gel in the electrospinning solutions. The effects of ZnO-NPs in the physico-chemical, mechanical and in vitro biological properties of composite membranes were studied. The composite membranes showed adequate mechanical properties to offer a satisfactory clinical manipulation and an excellent conformability to the defect site while their degradation rate seemed to be appropriate to allow successful regeneration of periodontal defects. The presence of ZnO-NPs in the composite membranes significantly decreased the planktonic and the biofilm growth of the Staphylococcus aureus over time. Finally, the viability of human osteoblasts and human gingival fibroblasts exposed to the composite membranes with 1 and 3 wt% of ZnO-NPs indicated that those membranes are not expected to negatively influence the ability of periodontal cells to repopulate the defect site during GTR treatments. The results here obtained suggest that composite membranes of PCL and Gel loaded with ZnO-NPs have the potential to be used as structurally stable GTR membranes with local antibacterial properties intended for enhancing clinical treatments.

Single-step, acid-based fabrication of homogeneous gelatin-polycaprolactone fibrillar scaffolds intended for skin tissue engineering

Blends of natural and synthetic polymers have recently attracted great attention as scaffolds for tissue engineering applications due to their favorable biological and mechanical properties. Nevertheless, phase-separation of blend components is an important challenge facing the development of electrospun homogeneous fibrillar natural-synthetic polymers scaffolds; phase-separation can produce significant detrimental effects for scaffolds fabricated by electrospinning. In the present study, blends of gelatin (Gel; natural polymer) and polycaprolactone (PCL; synthetic polymer), containing 30 and 45 wt% Gel, were prepared using acetic acid as a 'green' sole solvent to straightforwardly produce appropriate single-step Gel-PCL solutions for electrospinning. Miscibility of Gel and PCL in the scaffolds was assessed and the morphology, chemical composition and structural and solid-state properties of the scaffolds were thoroughly investigated. Results showed that the two polymers proved miscible under the single-step solution process used and that the electrospun scaffolds presented suitable properties for potential skin tissue engineering applications. Viability, metabolic activity and protein expression of human fibroblasts cultured on the Gel-PCL scaffolds were evaluated using LIVE/DEAD (calcein/ethidium homodimer), MTT-Formazan and immunocytochemistry assays, respectively. In vitro results showed that the electrospun Gel-PCL scaffolds enhanced cell viability and proliferation in comparison to PCL scaffolds. Furthermore, scaffolds allowed fibroblasts expression of extracellular matrix proteins, tropoelastin and collagen Type I, in a similar way to positive controls. Results indicated the feasibility of the single-step solution process used herein to obtain homogeneous electrospun Gel-PCL scaffolds with Gel content ≥30 wt% and potential properties to be used as scaffolds for skin tissue engineering applications for wound healing.

Bacteriostatic Effect of Piezoelectric Poly-3-Hydroxybutyrate and Polyvinylidene Fluoride Polymer Films under Ultrasound Treatment

Antibiotic resistance of bacteria stimulates the development of new treatment approaches. Piezoelectric-catalysis has attracted much attention due to the possibility to effectively provide antibacterial effect via generation of reactive oxygen species. However, the influence of the surface charge or potential of a piezopolymer on bacteria has not been sufficiently studied so far. This study reports the fabrication and characterization of thin films of piezoelectric polyhydroxybutyrate, polyvinylidene fluoride, and polyvinylidene fluoride trifluoroethylene as well as non-piezoelectric polycaprolactone polymers fabricated using solution casting approach. The piezoelectric coefficient (d₃₃) and surface electric peak-to-peak potential generated by the cyclic mechanical stress applied to the films were measured. Neither any toxic effect of the polymer films nor ultrasound influence on Escherichia coli bacteria behavior is observed. However, significant inhibition of the growth of bacteria is revealed during mechanical stimulation of piezoelectric samples via ultrasound treatment. Thus, this study demonstrates clear bacteriostatic effect of piezoelectric polymers for different tissue engineering applications.

Sequential release of drugs form a dual-delivery system based on pH-responsive nanofibrous mats towards wound care

Using Chitosan/PEO as the shell and PCL as the core, chitosan–polyethylene oxide/polycaprolactone nanofibrous mats were prepared successfully by coaxial electrospinning for co-load and sequential co-delivery of two drugs.

A facile way for development of three-dimensional localized drug delivery system for bone tissue engineering

Removing malignant bone tumors results in critical size bone defects. These voids in bones should be filled by a proper scaffold that not only can support cell ingrowth and bone regeneration but also it has to show a desirable ability in long-term releasing anticancer drugs in order to prevent the growth of remaining cancer cells. Applying this scaffold can significantly improve the outcome of bone tumors treatment. In this study, a novel way is proposed for immobilization of doxorubicin (DOX)-loaded polycaproloactone (PCL) microparticles on the hardystonite (HT) scaffold surfaces. High interconnected porous HT scaffolds with immobilized DOX-encapsulated PCL microparticles can be successfully fabricated by modified water/oil/water method. In the present work, we verify a slow release of DOX over 30 days from PCL microparticles inside HT scaffold. Our developed HT scaffolds with the long-term release of DOX are more effective in reduction of Saos-2 cancer cells viability and induce higher degrees of apoptosis compared to DOX dip coated HT scaffolds. Encapsulating DOX into PCL microparticles significantly improves the anti-tumor activity of DOX by regulating the expression of apoptosis-related genes. Our results suggest that by immobilization of polymeric vehicles on the ceramic scaffold for controlled drug release, we can achieve high efficiency in apoptosis of cancer cells.

Oxygen-Scavenging Multilayered Biopapers Containing Palladium Nanoparticles Obtained by the Electrospinning Coating Technique

The main goal of this study was to obtain, for the first time, highly efficient water barrier and oxygen-scavenging multilayered electrospun biopaper coatings of biodegradable polymers over conventional cellulose paper, using the electrospinning coating technique. In order to do so, poly(3-hydroxybutyrate) (PHB) and polycaprolactone (PCL) polymer-containing palladium nanoparticles (PdNPs) were electrospun over paper, and the morphology, thermal properties, water vapor barrier, and oxygen absorption properties of nanocomposites and multilayers were investigated. In order to reduce the porosity, and to enhance the barrier properties and interlayer adhesion, the biopapers were annealed after electrospinning. A previous study showed that electrospun PHB-containing PdNP did show significant oxygen scavenging capacity, but this was strongly reduced after annealing, a process that is necessary to form a continuous film with the water barrier. The results in the current work indicate that the PdNP were better dispersed and distributed in the PCL matrix, as suggested by focus ion beam-scanning electron microscopy (FIB-SEM) experiments, and that the Pd enhanced, to some extent, the onset of PCL degradation. More importantly, the PCL/PdNP nanobiopaper exhibited much higher oxygen scavenging capacity than the homologous PHB/PdNP, due to most likely, the higher oxygen permeability of the PCL polymer and the somewhat higher dispersion of the Pd. The passive and active multilayered biopapers developed here may be of significant relevance to put forward the next generation of fully biodegradable barrier papers of interest in, for instance, food packaging.

Novel Biocompatible and Biodegradable PCL-PLA/ Iron Oxide NPs Marker Clip Composite for Breast Cancer Biopsy

Strength and biocompatibility of composite materials (using a polymer matrix) are used in medicine for various devices such as prostheses and marker clips (biomarkers). Marker clips indicate the site of a lesion in the body, specifically for breast cancer diagnosis or treatment. In general, marker clips are made of steel or titanium, but lately, materials containing biodegradable polymers had been proposed. Our hypothesis is that a copolymer of polylactic acid and poly(ε-caprolactone) (PLA-PCL) could be used as marker clip material. After evaluating different polymer rates performance, metallic nanoparticles (NPs) were included to enhance the stability of the best copolymer and a marker clip prototype was proposed. Characterization of nanoparticles was made by dynamic light scattering (DLS), X-ray diffraction (XRD) and magnetic measurements. Mechanical, thermal and radiopacity properties were evaluated for composites formulation. In vitro, radiopaque experiments showed that BM-2 composite had the best performance. In vivo experiments showed that, after five months, the marker clip prototype maintained its shape, visibility and contrast properties. In consequence, a novel formulation of composite (PLA-PCL/metallic nanoparticles) is suitable for further studies as an alternative material for marker clips for breast cancer lesions.

Design of Controllable Novel Piezoelectric Components for Microfluidic Applications

This paper reviews recent investigations and achievements in the design of controllable functional components for improving microfluidic systems, its effectiveness, and functionality. The main purpose was to design novel microstructures with piezoelectric properties (microresonators), which enable one to control the effectiveness of fluid flow in micro-hydro-mechanical devices for biomedical/biochemical purposes. Controllable properties were obtained by incorporating different types of binders in a piezoelectric ceramic matrix (lead zirconate titanate): polyvinyl butyral (PVB), poly methyl methacrylate (PMMA), and polystyrene (PS). The change in chemical composition of PZT helps to manipulate the piezoelectric characteristics, surface morphology, mechanical properties, etc., of the designed microfluidic element with the microstructure in it.