The Influence of Surface Wettability and Topography on the Bioactivity of TiO2/Epoxy Coatings on AISI 316L Stainless Steel

Composite Cryogels Based on Hydroxyapatite and Polyvinyl Alcohol and the Study of Physicochemical and Mechanical Properties

Nowadays, due to the increasing number of diseases and injuries related to bone tissue, there is an acute problem of creating a material that could be incorporated into the bone tissue structure and contribute to accelerated bone regeneration. Such materials can be represented by a polymeric matrix that holds the material in the bone and an inorganic component that can be incorporated into the bone structure and promote accelerated bone regeneration. Therefore, in this work we investigated polyvinyl alcohol-based composite cryogels containing an in situ deposited inorganic filler, hydroxyapatite. The freezing temperature was varied during the synthesis process. The composition of the components was determined by infrared spectroscopy and the phase composition by X-ray phase analysis, from which it was found that the main phase of the composite is hydroxyapatite and that the particle size decreases with increasing freezing temperature. The elemental composition of the surface is dominated by carbon, oxygen, phosphorus and calcium; no impurities of other elements not typical for polyvinyl alcohol/ hydroxyapatite cryogels were found. Higher mechanical properties and melting points were observed at -15 °C. Cryogenic treatment parameters did not affect cell viability; however, cell viability was above 80% in all samples.

Nano-based formulations of curcumin: elucidating the potential benefits and future prospects in skin cancer

Skin cancer refers to any malignant lesions that occur in the skin and are observed predominantly in populations of European descent. Conventional treatment modalities such as excision biopsy, chemotherapy, radiotherapy, immunotherapy, electrodesiccation, and photodynamic therapy (PDT) induce several unintended side effects which affect a patient's quality of life and physical well-being. Therefore, spice-derived nutraceuticals like curcumin, which are well tolerated, less expensive, and relatively safe, have been considered a promising agent for skin cancer treatment. Curcumin, a chemical constituent extracted from the Indian spice, turmeric, and its analogues has been used in various mammalian cancers including skin cancer. Curcumin has anti-neoplastic activity by triggering the process of apoptosis and preventing the multiplication and infiltration of the cancer cells by inhibiting some signaling pathways and thus subsequently preventing the process of carcinogenesis. Curcumin is also a photosensitizer and has been used in PDT. The major limitations associated with curcumin are poor bioavailability, instability, limited permeation into the skin, and lack of solubility in water. This will constrain the use of curcumin in clinical settings. Hence, developing a proper formulation that can ideally release curcumin to its targeted site is important. So, several nanoformulations based on curcumin have been established such as nanogels, nanoemulsions, nanofibers, nanopatterned films, nanoliposomes and nanoniosomes, nanodisks, and cyclodextrins. The present review mainly focuses on curcumin and its analogues as therapeutic agents for treating different types of skin cancers. The significance of using various nanoformulations as well non-nanoformulations loaded with curcumin as an effective treatment modality for skin cancer is also emphasized.

Fabrication and characterization of graphene oxide-based polymer nanocomposite coatings, improved stability and hydrophobicity

In this study, acrylic-epoxy-based nanocomposite coatings loaded with different concentrations (0.5-3 wt.%) of graphene oxide (GO) nanoparticles were successfully prepared via the solution intercalation approach. The thermogravimetric analysis (TGA) revealed that the inclusion of GO nanoparticles into the polymer matrix increased the thermal stability of the coatings. The degree of transparency evaluated by the ultraviolet-visible (UV-Vis) spectroscopy showed that the lowest loading rate of GO (0.5 wt.%) had completely blocked the incoming irradiation, thus resulting in zero percent transmittance. Furthermore, the water contact angle (WCA) measurements revealed that the incorporation of GO nanoparticles and PDMS into the polymer matrix had remarkably enhanced the surface hydrophobicity, exhibiting the highest WCA of 87.55º. In addition, the cross-hatch test (CHT) showed that all the hybrid coatings exhibited excellent surface adhesion behaviour, receiving 4B and 5B ratings respectively. Moreover, the field emission scanning electron microscopy (FESEM) micrographs confirmed that the presence of the functional groups on the GO surface facilitated the chemical functionalization process, which led to excellent dispersibility. The GO composition up to 2 wt.% showed excellent dispersion and uniform distribution of the GO nanoparticles within the polymer matrix. Therefore, the unique features of graphene and its derivatives have emerged as a new class of nanofillers/inhibitors for corrosion protection applications.

Biomimetic calcium phosphate coating on medical grade stainless steel improves surface properties and serves as a drug carrier for orthodontic applications

OBJECTIVE

Recently, stainless steel (SSL) miniscrew implants have been used in orthodontic clinics as temporary anchorage devices. Although they have excellent physical properties, their biocompatibility is relatively poor. Previously, our group developed a two-phase biomimetic calcium phosphate (BioCaP) coating that can significantly improve the biocompatibility of medical devices. This study aimed to improve the biocompatibility of SSL by coating SSL surface with the BioCaP coating.

METHODS

Titanium (Ti) discs and SSL discs (diameter: 5 mm, thickness: 1 mm) were used in this study. To form an amorphous layer, the Ti discs were immersed in a biomimetic modified Tyrode solution (BMT) for 24 h. The SSL discs were immersed in the same solution for 0 h, 12 h, 24 h, 36 h and 48 h. To form a crystalline layer, the discs were then immersed in a supersaturated calcium phosphate solution (CPS) for 48 h. The surface properties of the BioCaP coatings were analysed. In addition, bovine serum albumin (BSA) was incorporated into the crystalline layer during biomimetic mineralisation as a model protein.

RESULTS

The morphology, chemical composition and drug loading capacity of the BioCaP coating on smooth SSL were confirmed. This coating improved roughness and wettability of SSL surface. In vitro, with the extension of BMT coating period, the cell seeding efficiency, cell spreading area and cell proliferation on the BioCaP coating were increased.

SIGNIFICANCE

These in vitro results show that the BioCaP coating can improve surface properties of smooth medical grade SSL and serve as a carrier system for bioactive agents.

Effect of Polymer Coatings on the Permeability and Chloride Ion Penetration Resistances of Nano-Particles and Fibers-Modified Cementitious Composites

Nano-particles and fibers-modified cementitious composite (NFCC) can greatly overcome the shortcomings of traditional cementitious materials, such as high brittleness and low toughness, and improve the durability of the composite, which in turn increases the service life of the structures. Additionally, the polymer coatings covering the surface of the composite can exert a good physical shielding effect on the external water, ions, and gases, so as to improve the permeability and chloride ion penetration resistance of the composite. In this study, the effect of three types of polymer coatings on the water contact angle, permeability resistance, and chloride ion penetration resistance of the NFCC with varied water–binder ratios were investigated. Three kinds of polymers (chlorinated rubber coating, polyurethane coating, and silane coating) were applied in two types of coatings, including single-layer and double-layer coatings. Three water–binder ratios of 35 wt.%, 40 wt.%, and 45 wt.% were used for the NFCC. The research results revealed that the surface of the NFCC treated with polymer coatings exhibited excellent hydrophobicity. The permeability height and chloride diffusion coefficient of the NFCC coated with different types of polymer coatings were 31–48% and 36–47% lower, respectively, than those of the NFCC without polymer coatings. The durability of the NFCC was further improved when the polymer coatings were applied to the surface in two-layer. Furthermore, it was discovered that increasing the water–binder ratio of the NFCC would lessen the positive impact of polymer coatings on the durability of NFCC.

Poly(vinyl alcohol)/Plant Extracts Films: Preparation, Surface Characterization and Antibacterial Studies against Gram Positive and Gram Negative Bacteria

In this study, we aim to obtain biomaterials with antibacterial properties by combining poly(vinyl alcohol) with the extracts obtained from various selected plants from Romania. Natural herbal extracts of freshly picked flowers of the lavender plant (Lavandula angustifolia) and leaves of the peppermint plant (Mentha piperita), hemp plant (Cannabis sativa L.), verbena plant (Verbena officinalis) and sage plant (Salvia officinalis folium) were selected after an intensive analyzing of diverse medicinal plants often used as antibacterial and healing agents from the country flora. The plant extracts were characterized by different methods such as totals of phenols and flavonoids content and UV-is spectroscopy. The highest amounts of the total phenolic and flavonoid contents, respectively, were recorded for Salvia officinalis. Moreover, the obtained films of poly(vinyl alcohol) (PVA) loaded with plant extracts were studied concerning the surface properties and their antibacterial or cytotoxicity activity. The Attenuated Total Reflection Fourier Transform Infrared analysis described the successfully incorporation of each plant extract in the poly(vinyl alcohol) matrix, while the profilometry demonstrated the enhanced surface properties. The results showed that the plant extracts conferred significant antibacterial effects to films toward Staphylococcus aureus and Escherichia coli and are not toxic against fibroblastic cells from the rabbit.

Corrosion Resistance and Cytocompatibility of Magnesium-Calcium Alloys Modified with Zinc- or Gallium-Doped Calcium Phosphate Coatings

In orthopedic surgery, metals are preferred to support or treat damaged bones due to their high mechanical strength. However, the necessity for a second surgery for implant removal after healing creates problems. Therefore, biodegradable metals, especially magnesium (Mg), gained importance, although their extreme susceptibility to galvanic corrosion limits their applications. The focus of this study was to control the corrosion of Mg and enhance its biocompatibility. For this purpose, surfaces of magnesium-calcium (MgCa1) alloys were modified with calcium phosphate (CaP) or CaP doped with zinc (Zn) or gallium (Ga) via microarc oxidation. The effects of surface modifications on physical, chemical, and mechanical properties and corrosion resistance of the alloys were studied using surface profilometry, goniometry, scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), nanoindentation, and electrochemical impedance spectroscopy (EIS). The coating thickness was about 5-8 μm, with grain sizes of 43.1 nm for CaP coating and 28.2 and 58.1 nm for Zn- and Ga-doped coatings, respectively. According to EIS measurements, the capacitive response (Y_c) decreased from 11.29 to 8.72 and 0.15 Ω^-1 cm^-2 sⁿ upon doping with Zn and Ga, respectively. The E_corr value, which was -1933 mV for CaP-coated samples, was found significantly electropositive at -275 mV for Ga-doped ones. All samples were cytocompatible according to indirect tests. In vitro culture with Saos-2 cells led to changes in the surface compositions of the alloys. The numbers of cells attached to the Zn-doped (2.6 × 10⁴ cells/cm²) and Ga-doped (6.3 × 10⁴ cells/cm²) coatings were higher than that on the surface of the undoped coating (1.0 × 10³ cells/cm²). Decreased corrosivity and enhanced cell affinity of the modified MgCa alloys (CaP coated and Zn and Ga doped, with Ga-doped ones having the greatest positive effect) make them novel and promising candidates as biodegradable metallic implant materials for the treatment of bone damages and other orthopedic applications.

Development of Mechanical, Corrosion Resistance, and Antibacterial Properties of Steels

The total cost and environmental consequences of corrosion problems have become a major challenge to engineers [...].

Anodized Biomedical Stainless-Steel Mini-Implant for Rapid Recovery in a Rabbit Model

The study aimed to analyze the recovery period of the anodized 316L biomedical stainless steel (BSS) mini-implant through its implantation on femur of rabbit model. The 316L BSS mini-implant was modified by an electrochemical anodization approach with different voltages. The anodized samples were characterized via field-emission scanning electron microscopy, X-ray diffractometry, and X-ray photoelectron spectroscopy. The biocompatibility was assessed by cell culture assay. The anodized mini-implant was implanted on rabbit’s femur then evaluated histologically after 4 and 8 weeks. Analytical results indicated that the topography of the anodized mini-implant at 5 V for 5 min consisted of a dual (micro/nano) porous structure. Oxide film of Cr2O3 was formed on the surface of anodized mini-implant after anodizing with 5 V for 5 min. In vitro cell culture assay revealed that fibroblast cells (NIH-3T3) on the anodized samples were more firmly attached as compared with the control sample. Moreover, histological analysis demonstrated that the anodized mini-implant improved bone recovering at 4 weeks after implantation. Thus, this study suggests that the anodized 316L BSS mini-implant could be a potential choice as anchorage device for effective and efficient orthodontic treatment.

Hierarchical Microtextures Embossed on PET from Laser-Patterned Stamps

Nowadays, the demand for surface functionalized plastics is constantly rising. To address this demand with an industry compatible solution, here a strategy is developed for producing hierarchical microstructures on polyethylene terephthalate (PET) by hot embossing using a stainless steel stamp. The master was structured using three laser-based processing steps. First, a nanosecond-Direct Laser Writing (DLW) system was used to pattern dimples with a depth of up to 8 µm. Next, the surface was smoothed by a remelting process with a high-speed laser scanning at low laser fluence. In the third step, Direct Laser Interference Patterning (DLIP) was utilized using four interfering sub-beams to texture a hole-like substructure with a spatial period of 3.1 µm and a depth up to 2 µm. The produced stamp was used to imprint PET foils under controlled temperature and pressure. Optical confocal microscopy and scanning electron microscopy imaging showed that the hierarchical textures could be accurately transferred to the polymer. Finally, the wettability of the single- and multi-scaled textured PET surfaces was characterized with a drop shape analyzer, revealing that the highest water contact angles were reached for the hierarchical patterns. Particularly, this angle was increased from 77° on the untreated PET up to 105° for a hierarchical structure processed with a DLW spot distance of 60 µm and with 10 pulses for the DLIP treatment.

Surface Modification of 316L SS Implants by Applying Bioglass/Gelatin/Polycaprolactone Composite Coatings for Biomedical Applications

In this study, various composites of bioglass/gelatin/polycaprolactone (BG/GE/PCL) were produced and coated on the surface of 316L stainless steel (SS) to improve its bioactivity. X-ray diffractometry (XRD), scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS) were utilized to characterize the specimens. The results showed that bioglass particles were distributed uniformly in the coating. By increasing the wt.% of bioglass in the nanocomposite coatings, the surface roughness and adhesion strength increased. The corrosion behavior of GE/PCL (PCL-10 wt.% gelatin coated on 316L SS) and 3BG/GE/PCL (GE/PCL including 3 wt.% bioglass coated on 316L SS) samples were studied in PBS solution. The results demonstrated that 3BG/GE/PCL sample improved the corrosion resistance drastically compared to the GE/PCL specimen. In vitro bioactivity of samples was examined after soaking the specimens for 7, 14 and 28 days in simulated body fluid (SBF). The results showed a significant apatite formation on the surface of 3BG/GE/PCL samples. The cell viability evaluation was performed using 3- (4, 5-dimethylthiazol-2-yl)-2,5 diphenyltetrazoliumbromide (MTT) tests which confirmed the enhanced cell viability on the surface of 3BG/GE/PCL samples. The in vivo behavior of specimens illustrated no toxicity and inflammatory response and was in a good agreement with the results obtained from the in vitro test.

Graphene–Chitosan Hybrid Dental Implants with Enhanced Antibacterial and Cell-Proliferation Properties

Dental implants are widely used tooth replacement tools owing to their good oral rehabilitation and reconstruction capacities. Since dental implants are designed as a replacement for natural teeth, multi-functional abilities are desired to achieve successful implant treatment with improved osseointegration through promotion of mammalian cell activity and prevention of bacterial cell activity. In this study, we developed a graphene–chitosan hybrid dental implant (GC hybrid implant) using various concentrations of graphene, which demonstrated the different surface properties including increased wettability and roughness. Importantly, the GC hybrid implant under the optimal condition (i.e., 1% GC hybrid implant) could significantly promote osteoblast proliferation while reducing biofilm formation and bacterial activity. Our study demonstrates the potential of using this GC hybrid implant as a new type of dental implant, which can offer an effective design for the fabrication of advanced dental implants.

Antibacterial Films Based on PVA and PVA-Chitosan Modified with Poly(Hexamethylene Guanidine)

In this study, thin, polymeric films consisting of poly(vinyl alcohol) (PVA) and chitosan (Ch) with the addition of poly(hexamethylene guanidine) (PHMG) were successfully prepared. The obtained materials were analyzed to determine their physicochemical and biocidal properties. In order to confirm the structure of PHMG, nuclear magnetic resonance spectroscopy (1H NMR) was applied, while in the case of the obtained films, attenuated total reflectance infrared spectroscopy with Fourier transform (FTIR-ATR) was used. The surface morphology of the polymer films was evaluated based on atomic force microscopy. Furthermore, the mechanical properties, color changes, and thermal stability of the obtained materials were determined. Microbiological tests were performed to evaluate the biocidal properties of the new materials with and without the addition of PHMG. These analyses confirmed the biocidal potential of films modified by PHMG and allowed for comparisons of their physicochemical properties with the properties of native films. In summary, films consisting of PVA and PHMG displayed higher antimicrobial potentials against Gram-positive (Staphylococcus aureus) and Gram-negative (Escherichia coli) bacteria in comparison to PVA:Ch-based films with the addition of PHMG.

Fast Surface Hydrophilization via Atmospheric Pressure Plasma Polymerization for Biological and Technical Applications

Polymeric surfaces can benefit from functional modifications prior to using them for biological and/or technical applications. Surfaces considered for biocompatibility studies can be modified to gain beneficiary hydrophilic properties. For such modifications, the preparation of highly hydrophilic surfaces by means of plasma polymerization can be a good alternative to classical wet chemistry or plasma activation in simple atomic or molecular gasses. Atmospheric pressure plasma polymerization makes possible rapid, simple, and time-stable hydrophilic surface preparation, regardless of the type and properties of the material whose surface is to be modified. In this work, the surface of polypropylene was coated with a thin nanolayer of plasma-polymer which was prepared from a low-concentration mixture of propane-butane in nitrogen using atmospheric pressure plasma. A deposition time of only 1 second was necessary to achieve satisfactory hydrophilic properties. Highly hydrophilic, stable surfaces were obtained when the deposition time was 10 seconds. The thin layers of the prepared plasma-polymer exhibit highly stable wetting properties, they are smooth, homogeneous, flexible, and have good adhesion to the surface of polypropylene substrates. Moreover, they are constituted from essential elements only (C, H, N, O). This makes the presented modified plasma-polymer surfaces interesting for further studies in biological and/or technical applications.