The odontogenic differentiation of human dental pulp stem cells on hydroxyapatite-coated biodegradable nanofibrous scaffolds

The authors aimed to design nanofibrous (NF) scaffolds that facilitate odontogenic and osteogenic differentiation of human dental pulp-derived mesenchymal stem cells (DPSCs) in vitro. For this purpose, hydroxyapatite (HA)–loaded poly (L-lactic acid)/poly (?-caprolactone) (PLLA:PCL 2;1) blend NFs were prepared using the electrospinning method. Alizarin red activity and cell viability were evaluated by MTT assay, and SEM revealed the proliferation properties of NF scaffolds. QRT-PCR results demonstrated that HA-loaded PLLA/PCL can lead to osteoblast/odontoblast differentiation in DPSCs through the up-regulation of related genes, thus indicating that electrospun biodegradable PCL/PLA/HA has remarkable prospects as scaffolds for bone and tooth tissue engineering.     

Development of a novel smart carrier for drug delivery: Ciprofloxacin loaded vaterite/reduced graphene oxide/PCL composite coating on TiO2 nanotube coated titanium

In the field of orthopaedic implants, post-surgery infections and biocompatibility are the most challenging obstacles. Sustained and controlled antibiotic release is a key factor in novel drug delivery systems. A novel drug delivery system combined with vaterite microsphere, graphite oxide (GO), reduced graphene oxide (rGO) incorporated in a polycaprolactone (PCL) matrix on TiO₂ nanotube coated Ti (TNT-Ti) is established. Anodization was employed to develop TiO₂ nanotubular arrays on Ti. Ciprofloxacin hydrochloride (CPF–HCl) loaded vaterite microspheres were synthesized by in situ precipitation method. Deposition of vaterite/PCL, vaterite-GO/PCL and vaterite-rGO/PCL composite coating on TNT-Ti was carried out by dip coating method. The composite coatings were characterized for their phase content, morphological features and functional groups. Among the three types of composite coatings, vaterite-rGO/PCL composite coating is found to be capable of encapsulating CPF-HCl to a level of 75.14 μg. The drug release profile of CPF-HCl from the vaterite-rGO/PCL composite coating exhibits a controlled release amounting to only 35.02 % of release at the end of 120 h. The vaterite-rGO/PCL composite coating exhibits a low dissolution rate and possesses adequate bioactivity in HBSS and SBF solutions at 37 °C for 14 and 10 days, respectively. The in situ loaded CPF-HCL drug on vaterite microspheres, PCL polymer matrix and GO/rGO nanofillers does not affect the cytocompatibility and all the composite coatings supported cell viability and proliferation. The ability of vaterite-rGO/PCL composite coating to provide a slow and steady release of antibiotics with sufficient bioactivity and biocompatibility at the tissue implant interface makes it a promising for osteomyelitis infection of bone tissue implant materials.     

β-TCP scaffold coated with PCL as biodegradable materials for dental applications

Requirements for an ideal scaffold include biocompatibility, biodegradability, mechanical strength and sufficient porosity and pore dimensions. Beta tricalcium phosphate (β-TCP) has competent biocompatibility and biodegradability, but has low mechanical strength because of its porous structure. Polycaprolactone (PCL) is a biodegradable polymer with elastic characteristics and good biocompatibility. In this study, β-TCP/PCL composites were prepared in different ratio and their morphology, phase content, mechanical properties, biodegradation and biocompatibility were investigated. After coating, surfaces of β-TCP scaffolds were covered with the PCL while some of the pores were partially clogged. The compression and bending strength of β-TCP scaffolds were significantly enhanced by PCL coating. The degradation rate of the scaffold in Tris buffer was reduced with higher content of the PCL coating. MTT and ALP assays showed that the osteoblast cells could proliferate and differentiate on PCL coated scaffolds as well as on bare β-TCP scaffolds. Based on the comprehensive analysis achieved in this study, it is concluded that the β-TCP/PCL composite scaffold fabricated with 40% β-TCP and 5% PCL exhibits optimum properties suitable for dental applications.     

Electrospun Poly(ε-Caprolactone)/Silk Fibroin Coaxial Core-Sheath Nanofibers Applied to Scaffolds and Drug Carriers

Developing biologically mimetic nanofibers (NFs) is crucial for their applications as scaffolds in tissue engineering and drug carriers. Herein, we present a strategy to facilely fabricate core-sheath NFs using coaxial electrospinning technique. Poly(ε-caprolactone) (PCL) and silk fibroin (SF) were employed as component materials to construct PCL/SF NFs with PCL cores uniformly encapsulated by SF sheaths. Scanning electron microscopy and transmission electron microscopy demonstrate a uniform core-sheath structure of the coaxial NFs. The engineered core-sheath structure confers the composite NFs with greatly improved properties including surface hydrophilicity and mechanical properties. In vitro cell culture validates that the core-sheath NFs are favorable to the cultured rat pheochromocytoma cells (PC 12) attachment. To further demonstrate the advantage of the coupled structural integrity, the PCL/SF core-sheath NFs were compared with the NFs produced from PCL and SF blend. Results showed that the PCL/SF NFs possessed a tensile strength of ~6.93 ± 0.52 MPa and an elongation at break of ~294.31 ± 24.17%, whereas the blend NFs possessed ~5.55 ± 0.50 MPa and ~88.05 ± 13.98%, respectively. Dexamethasone-phosphate sodium (DEX) was employed as a model drug, whereby the in vitro release study indicates that the NFs exhibit an ideal releasing profile, capable of releasing DEX continuously over a period of 450 h. The constructed PCL/SF core-sheath NFs are promising candidates for biomedical applications. POLYM. ENG. SCI., 60:802–809, 2020. © 2020 Society of Plastics Engineers     

Novel water-dispersible glycidyl carbamate (GC) resins and waterborne amine-cured coatings

Water-dispersible glycidyl carbamate (GC) functional resins were synthesized and crosslinked using a water-dispersible amine to form coatings. GC functional resins are synthesized by the reaction of an isocyanate functional compound with glycidol to yield a carbamate (urethane) linkage (–NHCO–) and reactive epoxy group. The combination of both functionalities in a single resin structure imparts excellent mechanical and chemical properties to the coatings. Previous studies on the development of GC coatings have focused on solvent-borne coating systems. In this study, GC resins were modified by incorporating nonionic hydrophilic groups to produce water-dispersible resins. To determine the influence of the content of hydrophilic groups on dispersion stability, aqueous dispersions were made from a series of hydrophilically modified GC resins and characterized for particle size and dispersion stability. The composition of a typical, dispersed GC resin particle was predicted using Monte Carlo simulations. Stable GC dispersions were used to prepare amine-cured coatings. The coatings were characterized for solvent resistance, water resistance, hardness, flexibility, adhesion, and surface morphology. It was observed that GC resins were able to be dispersed in water without using any surfactant and by minimal mixing force (hand mixing) and produced coating films with good properties when crosslinked with a compatible waterborne amine crosslinker.     

Effect of composite coating with poly-dopamine/PCL on the corrosion resistance of magnesium

We report the use of poly(ε-caprolactone) (PCL) and poly-dopamine (PD) as a protective coating that inhibits corrosion of the underlying magnesium metal. The PD coating layer also improved the adhesion of the PCL layer, which has been found to have a significant effect on corrosion behavior. In this study, electrochemical methods were employed to investigate the corrosion behavior of Mg after applying PCL composite coatings. Potentiodynamic polarization measurements determined that the PCL coating pretreated with PD effectively inhibited metal corrosion. In addition, the coating layer with improved adhesion has shown the possibility of inhibiting metal corrosion.     

Influence of mixing ratio on the permeability of water and the corrosion performance of epoxy/amine coated un-pretreated Al-2024 evaluated by impedance spectroscopy

Water uptake by epoxy coatings was measured in 0.5 M NaCl solution using a single frequency (1 kHz) capacitance method. The influence of substrates as well as the epoxy/amine mixing ratio on the water permeation coefficient was studied. Corrosion reactions at the coating/substrate interface affected the results of water uptake when the coating is applied on Al-2024 alloy. Consequently, the permeation coefficient of supported coating can be determined accurately only if the coating is applied on an inert substrate. Excess of epoxy or amine improves the solubility of water in the coating. A low water permeation coefficient was obtained with an epoxy/amine mixing ratio 1.05/1. But this formulation has a relatively poor corrosion performance when applied on an un-pretreated Al-2024 alloy. Under-film corrosion which is the characteristic of defective coatings was observed using electrochemical impedance spectroscopy.     

Cellulose monoacetate/polycaprolactone and cellulose monoacetate/polycaprolactam blended nanofibers for protease immobilization

Enzymes can be used multiple times when they are immobilized on a support. More enzymes can be immobilized on a surface when nanofibers are used as a supporting surface because the specific surface area increases tremendously. In this regard, polycaprolactam/cellulose monoacetate (PA6/CMA) and polycaprolactone/cellulose monoacetate (PCL/CMA) blended nanofibers (NFs) were prepared via an electrospinning process. Protease enzymes were immobilized on neat PA6, PCL, PA6/CMA, and PCL/CMA nanofibers and glutaraldehyde (GA) activated analogs through the physical adsorption method. The immobilized enzyme activity was measured by using a casein substrate, and the results were compared with free enzyme activity. Among all of the samples, the highest immobilization yield of about 82% was obtained with GA‐activated neat PCL NF samples. The best remaining activity of the immobilized enzymes on pure CMA NFs was found to be 59% after seven reuses. Even after nine reuses, enzyme activities are still observed on the CMA NF samples. It was expected that the addition of CMA in PCL and PA6 NFs would increase the reusability number to reach the reusability of CMA NFs, but it was not significantly enhanced. If CMA chains could be mostly collected on the sheath or close to the sheath of the NFs during the electrospinnig process, this target could be achieved. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45479.     

Investigating the role of key ingredients on cathodic delamination resistance of high-build pigmented epoxy coatings

Organic coatings applied on cathodically protected metallic structures must have good resistance to cathodic delamination or disbonding (CD). Both environmental conditions and coating composition influence the CD resistance. In the present study, the effect of types of epoxy resin, curing agents and their mixing ratio on cathodic delamination rate was studied in a high-build pigmented coating. Furthermore, the influence of platey fillers on CD resistance was also studied. In order to bring out correlations, if any, between adhesion and CD resistance, pull-off adhesion strengths (both dry and wet) of these coatings were also measured. Fairly good correlation was found between residual (wet) pull-off adhesion strength and CD resistance. When tested at 60 and 90°C, all the coatings under investigation showed chalking. Among the coatings under investigation, the one based on Bisphenol F epoxy and modified cycloaliphatic amine adduct exhibited excellent CD resistance.     

Biodegradable nanofibrous scaffolds as smart delivery vehicles for amino acids

The encapsulation of amino acids (AAs) and their correct preservation before they are ingested are challenging tasks. Nonpolar (l ‐alanine and l ‐phenylalanine), polar (l ‐cysteine hydrochloride and l ‐asparagine), and charged (l ‐lysine hydrochloride and l ‐aspartic acid) AAs were loaded into biodegradable and nontoxic poly(tetramethylene succinate) (PE44) nanofibers (NFs) with electrospinning. The loading of AAs considerably affected the morphology, topography, thermal properties, and wettability of the PE44 NFs. Furthermore, although the AAs crystallized in a phase separated from the polymeric matrix, the distribution of such crystals changed into PE44 NFs and depended on their chemical nature. Release assays in enzyme‐free solutions provided evidence that very significant amounts of AAs were retained in the NFs after 7 days, whereas assays in the lipase‐containing solution (because lipase performs essential roles in the digestion) showed almost complete release after a few hours. Lipase preferentially attacked the PE44 regions responsible for the retention of AAs in the biphasic system and favored the almost immediate release of the biomolecules. The results displayed in this study, combined with the biocompatibility, biodegradability, and potential use of the PE44 NFs as edible nonnutritional elements, suggest that the loaded PE44–AA NFs could be used to supply essential and conditional AAs. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44883.     

The role of the photoinitiating systems towards the inhibiting effect of phenolic compounds in the photopolymerization of acrylates

Photopolymerization reactions of wood coatings under UV and visible light have been carried out. The influence of model phenolic derivatives found in wood extractives on the polymerization kinetics as well as the coating properties of clear coating formulations exposed to light in laboratory and industrial type conditions has been discussed as a function of various UV/visible or visible photoinitiating systems based on ketones and dyes. The properties of suitable formulations are discussed. Several kinds of efficient photoinitiating systems are particularly investigated such as isopropylthioxanthone/amine; bis-acylphosphine oxide derivative/isopropylthioxanthone/amine and Rose Bengal/amine/additive.     

PHBV/PCL共混纤维的结构与性能

采用熔融纺丝法制备聚羟基丁酸戊酸酯(PHBV)/聚ε-己内酯(PCL)生物可降解共混纤维。采用差示扫描量热仪、广角X射线衍射仪、热台偏光显微镜和傅立叶变换红外光谱仪对PHBV/PCL共混体系的相容性和结晶性能进行了表征。结果表明:PHBV和PCL是不相容的;PHBV/PCL共混体系中的PHBV影响了PCL的结晶机制和结晶速率,PCL的结晶形态没有改变;PCL不影响PHBV的结晶机制,降低了PHBV的结晶速率,改变了PHBV的结晶形态。     

Studies on Silicon Containing Nano-hybrid Epoxy Coatings for the Protection of Corrosion and Bio-Fouling on Mild Steel

An epoxy nano-composite coating was developed using amine functionalized nZnO (in the amount of 2.5 %, 5.0 % and 7.5 wt %) as the dispersed phase and a commercially available epoxy resin as the matrix phase. The structural features of these materials were ascertained by FT-IR spectral studies. The anti-corrosive properties of the epoxy/nZnO hybrid coatings in comparison with a virgin coating were investigated by a salt spray test and electrochemical impedance spectroscopy technique. The surface morphology determined by SEM, indicates that nZnO particles were dispersed homogenously through the epoxy polymer matrix. The results showed improved antifouling and anticorrosive properties for epoxy-nZnO hybrid coatings.     

Design of tailored biodegradable implants: The effect of voltage on electrodeposited calcium phosphate coatings on pure magnesium

Magnesium, as a biodegradable metal, offers great potential for use as a temporary implant material, which dissolves in the course of bone tissue healing. It can sufficiently support the bone and promote the bone healing process. However, the corrosion resistance of magnesium implants must be enhanced before its application in clinical practice. A promising approach of enhancing the corrosion resistance is deposition of bioactive coating, which can reduce the corrosion rate of the implants and promote bone healing. Therefore, a well-designed substrate-coating system allowing a good control of the degradation behavior is highly desirable for tailored implants for specific groups of patients with particular needs. In this contribution, the influence of coating formation conditions on the characteristics of potentiostatically electrodeposited CaP coatings on magnesium substrate was evaluated. Results showed that potential variation led to formation of coatings with the same chemical composition, but very different morphologies. Parameters that mostly influence the coating performance, such as the thickness, uniformity, deposits size, and orientation, varied from produced coating to coating. These characteristics of CaP coatings on magnesium were controlled by coating formation potential, and it was demonstrated that the electrodeposition could be a promising coating technique for production of tailored magnesium-CaP implants.     

Physical properties of poly(?-caprolactone) coalesced from its α-cyclodextrin inclusion compound

Poly(?-caprolactone) (PCL) is a biodegradable/bioabsorbable polyester used in such biomedical applications as drug delivery and suture manufacturing. PCL has relatively poor physical properties, however, limiting its load-bearing applications. In this work, PCL was processed with α-cyclodextrin (α-CD) to form an inclusion complex (IC). The host α-CD was then stripped away to yield bulk PCL with largely extended, un-entangled polymer chains, a process referred to as coalescence. The changes in thermal, physical, and solid-state rheological properties resulting from this coalescence process were examined. It was found that elongating and un-entangling the PCL chains in this manner resulted in substantial increases in melt-crystallization temperatures, T_cs, up to 25 °C, depending on the cooling rate from the melt. Coalescence also increased the elastic storage modulus, decreased tan δ, increased the average hardness and Young’s modulus by 33 and 53%, respectively, and produced a closer packing of chains in the non-crystalline sample regions, without affecting the overall PCL crystallinity. Interestingly, the reorganized PCL chains in the non-crystalline regions of coalesced samples did not revert to the normal randomly-coiled entangled melt even after heating well above T_m (90 °C) for a month. The addition of small amounts (a few wt%) of coalesced PCL was also found to effectively nucleate the melt-crystallization of as-received PCL. Thus, the semi-crystalline morphology of PCL may be controlled by melt-processing with coalesced PCL added as a nucleant, that is not only necessarily non-toxic and biodegradable/bioabsorbable, but is also chemically compatible.     

The effect of bioactive glass nanoparticles on corrosion barrier performance and bioactivity of zinc oxide coatings electrodeposited on Ti6Al4V substrate

Zinc oxide coatings were electrodeposited on Ti6Al4V substrates from a nitrate bath with and without 1 wt% BG nanoparticles at ?1.2 and ?1.4 V_Ag/AgCl, where the former voltage created a spherical morphology, the latter developed a flower-like one. The spherical morphology was modified through the incorporation of BG nanoparticles, where surface roughness, wettability, and adhesion strength of the coating were enhanced. The coatings with spherical morphology also revealed complete barrier property after immersion in PBS solution. However, fully adverse effects were found for the coatings deposited at ?1.4 V_Ag/AgCl. This indicates that morphology is the most important factor determining the properties of ZnO and ZnO-BG coatings. The highest corrosion barrier performance was achieved for the ZnO-BG composite coating with spherical morphology. Although the composite coating with flower-like morphology did not provide complete barrier property at short immersion times, it earned that at longer times due to the plugging supported by the BG nanoparticles. The bioactivity tests in SBF at long times showed that the formation of Ca-P deposits on the surface of the composite coatings was noticeably improved.     

Biodegradable polycaprolactone/cuttlebone scaffold composite using salt leaching process

We prepared biodegradable polycaprolactone/cuttlebone scaffold composite by salt leaching process. In the first step, a co-continuous blend of biodegradable materials, polycaprolactone (PCL) and cuttlebone (CB), and an amount of sodium chloride salt particles were mixed using a stirrer. Next, the extraction of mineral salts using de-ionized distilled water was performed using a biodegradable PCL/CB scaffold with fully interconnected pores. Finally, the durable morphology of the scaffolds was fabricated by freeze-drying process at ?53 °C for 24 hrs in a vacuum. In addition, the quadrilateral pres ranged from about 250 to 300 ??m in diameter. Scanning electron microscopy (SEM) and mercury intrusion porosimeter techniques were carried out to characterize the pore morphology. By increasing the CB and sodium chloride salt particle content, the number of interconnected pores, material properties, and pore morphology were dramatically changed. The average compressive strengths (load at 50% strain) of the different porous PCL/CB scaffolds were found to decrease from 133 to about 79 (load at 50% strain, gf) with an increase in porosity. The values of the porosity increased as the sodium chloride salt volume fraction increased     

Electrical behavior of PET films coated with nanostructured organic–inorganic hybrids

Hybrid coatings, based on poly(ethylene oxide) (PEO) or polycaprolactone (PCL) and silica (SiO₂), at different organic–inorganic compositions have been used to coat PET films employed in the electric industry to produce capacitors. The overall electrical behavior of the coated films has been investigated. The electrical strength of the coated films increases up to 10–15% of the uncoated ones regardless of polymer type (PEO/PCL) and amount of inorganic phase, as far as the thickness of the coating is below 5 μm. A systematic increase of surface electrical conductivity is found in all coated samples which however still behave as insulators. Permittivity and loss factor also increase particularly at low frequencies (< 10 Hz) on account of the presence of ions deriving from the sol–gel process and on the presence of interfacial polarization probably related to the coatings nanostructurated morphology which leads to phase separation. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 4870–4877, 2006     

SLM Produced Porous Titanium Implant Improvements for Enhanced Vascularization and Osteoblast Seeding

To improve well-known titanium implants, pores can be used for increasing bone formation and close bone-implant interface. Selective Laser Melting (SLM) enables the production of any geometry and was used for implant production with 250-µm pore size. The used pore size supports vessel ingrowth, as bone formation is strongly dependent on fast vascularization. Additionally, proangiogenic factors promote implant vascularization. To functionalize the titanium with proangiogenic factors, polycaprolactone (PCL) coating can be used. The following proangiogenic factors were examined: vascular endothelial growth factor (VEGF), high mobility group box 1 (HMGB1) and chemokine (C-X-C motif) ligand 12 (CXCL12). As different surfaces lead to different cell reactions, titanium and PCL coating were compared. The growing into the porous titanium structure of primary osteoblasts was examined by cross sections. Primary osteoblasts seeded on the different surfaces were compared using Live Cell Imaging (LCI). Cross sections showed cells had proliferated, but not migrated after seven days. Although the cell count was lower on titanium PCL implants in LCI, the cell count and cell spreading area development showed promising results for titanium PCL implants. HMGB1 showed the highest migration capacity for stimulating the endothelial cell line. Future perspective would be the incorporation of HMGB1 into PCL polymer for the realization of a slow factor release.