In-Depth Characterization of Two Bioactive Coatings Obtained Using MAPLE on TiTaZrAg.

TiZrTaAg alloy is a remarkable material with exceptional properties, making it a unique choice among various industrial applications. In the present study, two types of bioactive coatings using MAPLE were obtained on a TiZrTaAg substrate. The base coating consisted in a mixture of chitosan and bioglass in which zinc oxide and graphene oxide were added. The samples were characterized in-depth through a varied choice of methods to provide a more complete picture of the two types of bioactive coating. The analysis included Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), ellipsometry, and micro-Raman. The Vickers hardness test was used to determine the hardness of the films and the penetration depth. Film adhesion forces were determined using atomic force microscopy (AFM). The corrosion rate was highlighted by polarization curves and by using electrochemical impedance spectroscopy (EIS). The performed tests revealed that the composite coatings improve the properties of the TiZrTaAg alloy, making them feasible for future use as scaffold materials or in implantology.

Carbon nanotubes conjugated with cisplatin activate different apoptosis signaling pathways in 2D and 3D-spheroid triple-negative breast cancer cell cultures: a comparative study.

The type of experimental model for the in vitro testing of drug formulations efficiency represents an important tool in cancer biology, with great attention being granted to three-dimensional (3D) cultures as these offer a closer approximation of the clinical sensitivity of drugs. In this study, the effects induced by carboxyl-functionalized single-walled carbon nanotubes complexed with cisplatin (SWCNT-COOH-CDDP) and free components (SWCNT-COOH and CDDP) were compared between conventional 2D- and 3D-spheroid cultures of human breast cancer cells. The 2D and 3D breast cancer cultures were exposed to various doses of SWCNT-COOH (0.25-2 µg/mL), CDDP (0.158-1.26 µg/mL) and the same doses of SWNCT-COOH-CDDP complex for 24 and 48 h. The anti-tumor activity, including modulation of cell viability, oxidative stress, proliferation, apoptosis, and invasion potential, was explored by spectrophotometric and fluorometric methods, immunoblotting, optical and fluorescence microscopy. The SWCNT-COOH-CDDP complex proved to have high anti-cancer efficiency on 2D and 3D cultures by inhibiting cell proliferation and activating cell death. A dose of 0.632 µg/mL complex triggered different pathways of apoptosis in 2D and 3D cultures, by intrinsic, extrinsic, and reticulum endoplasmic pathways. Overall, the 2D cultures showed higher susceptibility to the action of complex compared to 3D cultures and SWCNT-COOH-CDDP proved enhanced anti-tumoral activity compared to free CDDP.

Temperature-Controlled Chain Dynamics in Polyimide Doped with CoCl2 Probed Using Dynamic Mechanical Analysis.

Cobalt(II) chloride (CoCl2) being in the vicinity of polyimide chains entails modifications in terms of the molecular dynamics, which are mainly governed by the possible presence of amic acid residual groups, by the transition-metal-type characteristics of cobalt and by the CoCl2 content. Polyimide was synthesized using poly(amic acid) according to the reaction of 2,2'-bis(3,4-dicarboxylphenyl)hexafluoropropane dianhydride (6FDA) with 3,3'-dimethyl-4,4'-diaminodiphenylmethane (MMDA) in N,N-dimethylacetamide. CoCl2 was added before the thermal imidization of the poly(amic acid). An experimental approach was designed to establish the interaction between the polyimide and CoCl2 and whether the interaction depends on the quantity of the salt. Evidence for the existence of residual amic acid groups was obtained using second derivative Fourier Transform Infrared Spectroscopy (FTIR) and with the help of 2D correlation spectroscopy (2D-COS). Moreover, FTIR, along with X-ray photoelectron spectroscopy (XPS), revealed the interaction between the polymer and CoCl2, primarily in the form of Co(II)-N coordinated bonds. Nevertheless, the coordination of cobalt with suitable atoms from the amic acid groups is not precluded. The results of dynamic mechanical analysis (DMA) featured a specific relaxation assigned to the presence of CoCl2 in the polymeric film and demonstrated that its (non)reinforcing effect depends on its content in the polyimide.

Investigation of Shape Memory Polyurethane Properties in Cold Programming Process Towards Its Applications.

Thermoresponsive shape memory polymers (SMPs) with the remarkable ability to remember a temporary shape and recover their original one using temperature have been gaining more and more attention in a wide range of applications. Traditionally, SMPs are investigated using a method named often "hot-programming", since they are heated above their glass transition temperature (Tg) and after that, reshaped and cooled below Tg to achieve and fix the desired configuration. Upon reheating, these materials return to their original shape. However, the heating of SMPs above their Tg during a thermomechanical cycle to trigger a change in their shape creates a temperature gradient within the material structure and causes significant thermal expansion of the polymer sample resulting in a reduction in its shape recovery property. These phenomena, in turn, limit the application fields of SMPs, in which fast actuation, dimensional stability and low thermal expansion coefficient are crucial. This paper aims at a comprehensive experimental investigation of thermoplastic polyurethane shape memory polymer (PU-SMP) using the cold programming approach, in which the deformation of the SMP into the programmed shape is conducted at temperatures below Tg. The PU-SMP glass transition temperature equals approximately 65 °C. Structural, mechanical and thermomechanical characterization was performed, and the results on the identification of functional properties of PU-SMPs in quite a large strain range beyond yield limit were obtained. The average shape fixity ratio of the PU-SMP at room temperature programming was found to be approximately 90%, while the average shape fixity ratio at 45 °C (Tg - 20 °C) was approximately 97%. Whereas, the average shape recovery ratio was 93% at room temperature programming and it was equal to approximately 90% at 45 °C. However, the results obtained using the traditional method, the so-called hot programming at 65 °C, indicate a higher shape fixity value of 98%, but a lower shape recovery of 90%. Thus, the obtained results confirmed good shape memory properties of the PU-SMPs at a large strain range at various temperatures. Furthermore, the experiments conducted at both temperatures below Tg demonstrated that cold programming can be successfully applied to PU-SMPs with a relatively high Tg. Knowledge of the PU-SMP shape memory and shape fixity properties, estimated without risk of material degradation, caused by heating above Tg, makes them attractive for various applications, e.g., in electronic components, aircraft or aerospace structures.

Tri-Component Hydrogel as Template for Nanocrystalline Hydroxyapatite Deposition Using Alternate Soaking Method for Bone Tissue Engineering Applications.

Composite hydrogels containing apatite-like particles can act as scaffolds for osteoblast proliferation, with applications in bone tissue engineering. In this respect, porous biocompatible hydrogels were obtained from chitosan, oxidized pullulan, and PVA in different ratios. The stability of the hydrogels was ensured both by covalent bonds between aldehyde groups of oxidized pullulan and free amino groups of chitosan, and by physical bonds formed during freeze-thaw cycles and lyophilization. The deposition of calcium phosphates was performed by alternate soaking of the porous hydrogels into solutions with calcium and phosphate ions, assuring a basic pH required for hydroxyapatite formation. The mineralized hydrogels were characterized using FTIR spectroscopy, scanning electron microscopy, X-ray diffraction, and thermogravimetric analysis, showing that inorganic particles containing between 80 and 92% hydroxyapatite were deposited in a high amount on the pore walls of the polymeric matrix. The composition of the organic matrix influenced the crystallization of calcium phosphates and the mechanical properties of the composite hydrogels. In vitro biological tests showed that mineralized hydrogels support the proliferation of MG-63 osteoblast-like cells to a greater extent compared to pristine hydrogels.

Evidence through Thermal Analysis of Retro Diels-Alder Reaction in Model Networks Based on Anthracene Modified Polyester Resins.

The present work is focused on polyester resins obtained from the diglycidyl ether of bisphenol A and anthracene modified 5-maleimidoisophthalic acid. Because the maleimide-anthracene Diels-Alder (DA) adduct is stable at high temperatures, it is considered a good option for high performance polymers. However, the information related to the retroDA reaction for this type of adduct is sometimes incoherent. A detailed thermal study (conventional TGA, HiRes TGA, MTGA, DSC, MDSC) was performed in order to establish whether the rDA reaction can be revealed for this type of anthracene modified polyester resins. The TGA method confirmed the cleavage of the anthracene-maleimide DA adduct, while the DSC demonstrated the presence of anthracene in the system. At high temperatures, unprotected maleimide homopolymerizes and/or reacts with allyl groups according to the -ene reaction. Therefore, the thermal DA reaction is not displayed anymore upon the subsequent cooling, and the glass transition region is registered at a higher temperature range during the second heating. The use of sample-controlled thermal analysis (HiRes TGA) and MTGA improved the TGA result; however, it was not possible to separate the very complex degradation processes that are interconnected.

Thermal and Viscoelastic Responses of Selected Lignocellulosic Wastes: Similarities and Differences.

Woody lignocellulosic biomasses comprise the non-edible parts of fruit trees. In recent years, the exploitation of this biomass has been widening in order to mitigate environmental issues. At the same time, this waste could be transformed into a value-added product (active carbon by pyrolysis, isolation of nanocellulose, oils or proteins). For either valorization path, a complete thermo-mechanical characterization is required. A detailed thermo-mechanical study (TGA, DSC, DMA) was performed on two types of lignocellulosic wastes, with and without kernels: on one side, the walnut shells (WS) and the pistachio shells (PsS) and, in the second category, the apricot seeds (AS), the date seeds (DS), and the plum seeds (PS). The results of the sample-controlled thermal analyses (HiRes TGA) evidenced a better resolution of the degradation steps of WS. Kinetic studies conducted also by conventional TGA (Flynn-Wall-Ozawa) and modulated TGA (MTGA) allowed us to make comparative reasonings concerning the degradation of the investigated biomasses. The DMA results revealed the effect of water traces and oil kernels on relaxation and supported the atypical DSC endotherm emphasized in the freezing temperature domain.

Evaluation of the Sublimation Process of Some Purine Derivatives: Sublimation Rate, Activation Energy, Mass Transfer Coefficients and Phenomenological Models.

Caffeine and theophylline are compounds with important applications in the pharmaceutical industry and other fields of the chemical industry. These purine derivatives have simple chemical structures, therefore, the evaluation of their sublimation process contributes to the development of mass transfer analysis methods that can later be applied to other compounds with more complex structures. With the help of thermogravimetric analysis in isothermal conditions, the kinetic study of the sublimation of caffeine and theophylline, along with the evaluation of kinetic parameters (activation energy and the pre-exponential factor), was carried out. Global mass transfer coefficients were determined, which vary for caffeine between 53 × 10-8 and 631 × 10-8 mol/s·m2·Pa, and for theophylline between 68 × 10-8 and 441 × 10-8 mol/s·m2·Pa. The dimensionless equations of the form: Sh=a+b·Rec·Scd have been proposed, which allow the determination of individual mass transfer coefficients at temperatures between 130 and 160 °C for caffeine and between 170 and 200 °C for theophylline.

Interaction of Mg Alloy with PLA Electrospun Nanofibers Coating in Understanding Changes of Corrosion, Wettability, and pH.

A modified biodegradable magnesium alloy (AZ31, 96 wt% Mg, 3 wt% Al, and 1 wt% Zn) with polylactic acid (PLA) nanofibers was obtained by the electrospinning technique. The presence of PLA nanofibers was evidenced using Fourier transform infrared spectroscopy (FT-IR) and using an scanning electronic microscope (SEM) equipped with an energy dispersive X-ray spectroscopy (EDX) module. The degradation behavior of an uncoated Mg alloy and a Mg alloy coated with PLA was evaluated through hydrogen evolution, pH, and electrochemical measurements in simulated body fluid. Contact angle measurements showed a shift from hydrophilic towards the hydrophobic character of the alloy after its coating with PLA nanofibers. Furthermore, the electrochemical measurement results show that the Mg based alloy coated with PLA inhibits hydrogen evolution, thus being less prone to degradation. The aim of this research is not only to reduce the corrosion rate of Mg alloy and to improve its properties with the help of polylactic acid coating, but also to provide a study to understand the hydrophilic-hydrophobic balance of biodegradable magnesium based on surface energy investigations. Taking into account corrosion rate, wettability, and pH changes, an empiric model of the interaction of Mg alloy with PLA nanofibers is proposed.

Carboxyl-Functionalized Carbon Nanotubes Loaded with Cisplatin Promote the Inhibition of PI3K/Akt Pathway and Suppress the Migration of Breast Cancer Cells.

PI3K/Akt signaling is one of the most frequently dysregulated pathways in cancer, including triple-negative breast cancer. With considerable roles in tumor growth and proliferation, this pathway is studied as one of the main targets in controlling the therapies' efficiency. Nowadays, the development of nanoparticle-drug conjugates attracts a great deal of attention due to the advantages they provide in cancer treatment. Hence, the main purpose of this study was to design a nanoconjugate based on single-walled carbon nanotubes functionalized with carboxyl groups (SWCNT-COOH) and cisplatin (CDDP) and to explore the potential of inhibiting the PI3K/Akt signaling pathway. MDA-MB-231 cells were exposed to various doses (0.01-2 µg/mL SWCNT-COOH and 0.00632-1.26 µg/mL CDDP) of SWCNT-COOH-CDDP and free components for 24 and 48 h. In vitro biological tests revealed that SWCNT-COOH-CDDP had a high cytotoxic effect, as shown by a time-dependent decrease in cell viability and the presence of a significant number of dead cells in MDA-MB-231 cultures at higher doses. Moreover, the nanoconjugates induced the downregulation of PI3K/Akt signaling, as revealed by the decreased expression of PI3K and p-Akt in parallel with PTEN activation, the promotion of Akt protein degradation, and inhibition of tumor cell migration.

Binary Silicone Elastomeric Systems with Stepwise Crosslinking as a Tool for Tuning Electromechanical Behavior.

Interpenetrating polymer networks (IPNs) represent an interesting approach for tuning the properties of silicone elastomers due to the possible synergism that may occur between the networks. A new approach is presented, which consists of mixing two silicone-based networks with different crosslinking pathways; the first network being cured by condensation route and the second network by UV curing. The networks were mixed in different ratios and the resulted samples yield good mechanical properties (improved elongations, up to 720%, and Young's modulus, 1 MPa), thermal properties (one glass transition temperature, ~-123 °C), good dielectric strength (~50 V/µm), and toughness (63 kJ/m3).

Modulation of the PLLA Morphology through Racemic Nucleation to Reach Functional Properties Required by 3D Printed Durable Applications.

This paper presents an alternative for enhancing the durability of poly (L-lactide) (PLLA) by racemic nucleation following stereo-complexation with a selected poly (D-lactide) (PLDA). The compounds are obtained by melt blending of a PLLA grade, previously designed for 3D printing but with a low heat deflection temperature and impact resistance, with grades of PLDA differing in their molecular weight (Mw), D-lactide content (DS) and concentration. Our method considered how to reveal the racemic nucleation caused by stereo-complexation and its influence on functional properties. The FTIR study we performed showed that, depending on Mw, DS and concentration of the stereo-complexer (PDLA) used, bigger or smaller spectral changes can occur. The stereo-complexation was confirmed by the DSC analysis and, for the selected compound, by the POM, SEM, AFM microscopies, functional property and shapeability as 3D printing filaments. All the obtained results sustain the idea that, if a PLLA with Mw of 4.5 × 104 g·mol-1 is modified with PDLA with a medium Mw of 11.6 × 104 g·mol-1, medium DS of 4% and 1% concentration, a racemic nucleation is possible. It produces a racemic polylactic acid (PDLLA) with improved durability and good shapeability as 3D printing filaments. These results are explicable if the dependence of the intermolecular interactions appears between the PLLA and stereo-complexer PDLA. To enlarge the durable applicability of racemic polylactic acid (PDLLA), future research should identify other parameters controling the PLA stereo-complexing as the intensifying the mobility of the macromolecules, the finding of the optimal recemic cristalization window.

Dynamic Mechanical Analysis Investigations of PLA-Based Renewable Materials: How Are They Useful?

Interest in renewable polymers increased exponentially in the last decade and in this context poly(lactic acid) (PLA) became the leader mainly for practical reasons. Nevertheless, it is outstanding also from a scientific point of view, because its thermal and morphological properties are offering challenging new insights. With regard to dynamic mechanical analysis (DMA), PLA does not have the classical behavior of a thermoplastic polymer. Often, overlapping events (enthalpic relaxation, glass transition and crystallization) that occur as the temperature increases make the DMA result of a PLA look inexplicable even for polymer scientists. This review offers a perspective of the main phenomena that can be revealed in a DMA experiment and systematizes the information that can be obtained for every region (glassy, glass transition, rubbery, cold-crystallization and melting). Also, some unusual patterns registered in some cases will be commented upon. The review intends to offer indices that one should pay attention to in the interpretation of a DMA experiment, even if the investigator has only basic skills with DMA investigations.

Nanotubes and nano pores with chitosan construct on TiZr serving as drug reservoir.

Taking into account that modified and non modified TiZr alloys have a chance as alternatives for Ti as implant materials, this paper is focused on the elaboration and characterization of TiZr hybrid nanostructures (nanopores and nanotubes) loaded with gentamicin (GS) and covered with chitosan. FT-IR analysis permitted structure and corresponding bands identification. Scanning electronic microscopy (SEM) was used for morphology analysis and nanostrucure dimensions evaluations. The surface analysis was completed with roughness measurements, contact angle determinations and surface energy evaluations. The amount of drug released in both cases was measured using ultraviolet-visible spectroscopy (UV/Vis). The in-vitro drug release profile was applied to three kinetic mathematical models (Korsmeyer-Peppas, Peppas-Sahlin and Linder-Lippold). Using the experimental data on the three simulation models, the Lindner-Lippold was found to be the best suited for the transport mechanism dominated by Fickian diffusion. It was observed that the same quantity of gentamicin (approx. 95%) will be released in 10 days from nanopores and in 21 days from nanotubes, establishing in both cases longer term release as an expression of better targeted treatment of bone and osteomyelitis.

Influence of Matrigel on Single- and Multiple-Spheroid Cultures in Breast Cancer Research.

This study aimed to develop and compare single and multiple 3D models such as multicellular tumor spheroids and to investigate the influence of Matrigel on their morphological and functional behavior. MDA-MB-231 3D models were generated in the presence and absence of Matrigel and their key biological properties within 6 days of culture were monitored. Our results revealed the formation of well-defined 3D models in the presence of Matrigel, with a uniform morphology, increased diameter, good circularity, and increased expression of a proliferation marker (PCNA). In comparison, 3D models generated without Matrigel were characterized by an irregular border, reduced dimensions and circularity, and a decrease of PCNA expression. Similarities between the single and multiple 3D cultures were found in their viability, Nrf2 expression, and glutathione (GSH) content. The influence of Matrigel on MDA-MB-231 spheroids metabolism under hypoxic conditions was highlighted by released lactate dehydrogenase and nitric oxide, GSH levels and expression of Nrf2 and Hsp70 proteins. Based on the increased expression of PCNA and the development of the hypoxia process in the presence of extracellular matrix, our study showed that the addition of Matrigel improves the growing environment of tumor spheroids, making it closer to that of in vivo tumor conditions.

Zwitterionic Cysteine Drug Coating Influence in Functionalization of Implantable Ti50Zr Alloy for Antibacterial, Biocompatibility and Stability Properties.

The present paper aims atincreasing the bioperformance of implantable Ti50Zr alloy using zwitterionic cysteine drug coating. Aspects such as stability, biocompatibility, and antibacterial effects were investigated with the help of various methods such as infrared spectroscopy (FT-IR), scanning electronic microscopy (SEM), electrochemical methods, contact angle determinations and cell response. The experimental data of zwitterionic cysteine coating indicate the existence of a hydration layer due to hydrophilic groups evidenced in FT-IR which is responsible for the decrease of contact angle and antibacterial capabilities. The electrochemical stability was evaluatedbased on Tafel plots and electrochemical impedance spectroscopy (EIS). The cell response to cysteine was determined with gingival fibroblasts measuring lactate dehydrogenase (LDH) activity, concentrations of nitric oxide (NO) and intracellular level of reactive oxygen species (ROS). All experimental results supported the increase of stability and better cells response of implantable Ti50Zr alloy coated with zwitterionic cysteine drug. The antibacterial index was measured against Staphylococcus aureus and Escherichia coli. It was demonstrated that the coating enhanced the production of intracellular ROS in time, which subsequently caused a significant increase in antibacterial index.

Cisplatin Loaded Multiwalled Carbon Nanotubes Induce Resistance in Triple Negative Breast Cancer Cells.

In this paper we developed a method for multiwalled carbon nanotubes (MWCNTs) use as carriers for a drug based on platinum in breast cancer therapy. The method of functionalization involves the carboxyl functionalization of nanotubes and encapsulation of cisplatin (CDDP) into MWCNTs. The biological properties of MWCNTs loaded with CDDP (MWCNT-COOH-CDDP) and of individual components MWCNT-COOH and free CDDP were evaluated on MDA-MB-231 cells. Various concentrations of CDDP (0.316⁻2.52 µg/mL) and MWCNTs (0.5⁻4 µg/mL) were applied on cells for 24 and 48 h. Only at high doses of CDDP (1.26 and 2.52 µg/mL) and MWCNT-COOH-CDDP (2 and 4 µg/mL) cell morphological changes were observed. The cellular viability decreased only with approx. 40% after 48 h of exposure to 2.52 µg/mL CDDP and 4 µg/mL MWCNT-COOH-CDDP despite the high reactive oxygen species (ROS) production induced by MWCNTs starting with 24 h. After 48 h, ROS level dropped as a result of the antioxidant defence activation. We also found a significant decrease of caspase-3 and p53 expression after 48 h, accompanied by a down-regulation of NF-κB in cells exposed to MWCNT-COOH-CDDP system which promotes apoptosis escape and thus failing to overcome the triple negative breast cancer (TNBC) cells resistance.

Alkaline Phosphatase Immobilization on New Chitosan Membranes with Mg2+ for Biomedical Applications.

In this paper, we present the fabrication and characterization of new chitosan-based membranes while using a new biotechnology for immobilizing alkaline phosphatase (ALP). This technology involved metal ions incorporation to develop new biopolymeric supports. The chemical structure and morphological characteristics of proposed membranes were evaluated by infrared spectroscopy (FT-IR) and the scanning electron microscopy technique (SEM). The inductively coupled plasma mass spectrometry (ICP-MS) evidenced the metal ion release in time. Moreover, the effect of Mg2+ on the enzymatic activity and the antibacterial investigations while using Gram-negative Escherichia coli and Gram-positive Staphylococcus aureus bacteria, hemolysis, and biocompatibility behavior were studied. Immobilizing ALP into the chitosan membranes composition followed by the incorporation of Mg2+ led to polymeric supports with enhanced cellular viability when comparing to chitosan-based membranes without Mg2+. The results obtained evidenced promising performance in biomedical applications for the new biopolymeric supports that are based on chitosan, ALP, and metal ions.

Periodontal materials and cell biology for guided tissue and bone regeneration.

The present review is intended to find links between periodontal materials of the dentomaxillary apparatus and cell biology at the beginning of a century fraught with various forms of periodontal diseases and needing new treatment strategies. The manuscript has two different parts. The first describes the anatomy of tooth supporting structures, as well as related pathologies. The second part is related to cell and molecular biology in the context of periodontal regeneration.

Activity of vancomycin release from bioinspired coatings of hydroxyapatite or TiO2 nanotubes.

Herein we investigate the efficiency of various biomimetic coatings for localized drug delivery, using vancomycin as key therapeutic drug, which is a widely used antibiotic for the treatment of strong infections caused by positive Gram bacteria. We evaluate classical hydroxyapatite and biomimetic hydroxyapatite-collagen coatings obtained by electrochemical deposition as well as TiO2 nanotubes arrays obtained by electrochemical anodization. Surface morphology, compositional and structural data confirm the incorporation of vancomycin into the layers and drug release profiles for vancomycin evaluate their release ability. Namely, hydroxyapatite coatings lead to a ≈92% vancomycin release after 30h and hydroxyapatite-collagen to 85%, while the TiO2 nanotubes layers lead to 78% release. The antibacterial effect of such drug loaded coatings is evaluated against S. aureus (Gram-positive bacteria). Our study shows that the vancomycin incorporated hydroxyapatite coatings lead to a faster release, while the nanotubular coatings may lead to longer time release and additionally both types of coatings ensure a good antibacterial inhibition.