Silanization Process Research Articles

In Vitro and In Vivo Characterization of PLLA-316L Stainless Steel Electromechanical Devices for Bone Tissue Engineering-A Preliminary Study.

Bone injuries represent a major social and financial impairment, commonly requiring surgical intervention due to a limited healing capacity of the tissue, particularly regarding critical-sized defects and non-union fractures. Regenerative medicine with the application of bone implants has been developing in the past decades towards the manufacturing of appropriate devices. This work intended to evaluate medical 316L stainless steel (SS)-based devices covered by a polymer poly (L-lactic acid) (PLLA) coating for bone lesion mechanical and functional support. SS316L devices were subjected to a previously described silanization process, following a three-layer PLLA film coating. Devices were further characterized and evaluated towards their cytocompatibility and osteogenic potential using human dental pulp stem cells, and biocompatibility via subcutaneous implantation in a rat animal model. Results demonstrated PLLA-SS316L devices to present superior in vitro and in vivo outcomes and suggested the PLLA coating to provide osteo-inductive properties to the device. Overall, this work represents a preliminary study on PLLA-SS316L devices’ potential towards bone tissue regenerative techniques, showing promising outcomes for bone lesion support.

Effectiveness of Silanization and Plasma Treatment in the Improvement of Selected Flax Fibers' Properties.

The study investigated the effectiveness of the combination of chemical and physical methods of natural fibers’ modification. The long flax fibers were subjected to various types of modification. These were silanization, plasma modification and a combination of these methods. For the silanization process, two types of silanes were used: amino- and vinylsilane. The application of structurally different compounds allowed us to acquire knowledge about the effect of the modifier structure on its properties. Various properties of flax fibers were investigated, comparing the results before and after different modification processes. The flammability of prepared samples were tested by pyrolysis combustion flow calorimeter (PCFC). In the effect of the natural fibers’ modifications, flammability was reduced even by 30%. The thermal stability of modified fibers increased. The FTIR tests of the gases released during thermal degradation of the tested fibers allowed us to determine the important compounds and prove a lower degree of flax-fiber decomposition after modification. Flax fibers were also tested to evaluate their physical properties (linear mass, average diameter, aspect ratio and hygroscopicity). Changes in surface morphology were observed by scanning electron microscope (SEM). The properties of natural fibers improved significantly, thus contributing to an increase in their suitability for the use in composites.

Flexural Strength of an Indirect Composite Modified with Single-Wall Carbon Nanotubes.

The low resistance to fracture has limited the use of indirect composite resins for dental restorations, particularly in regions that are exposed to strong occlusal forces. To overcome this issue, different types of reinforcement for composites have been proposed, one of which is carbon nanotubes (CNTs). The aim of this study was to evaluate the flexural resistance of one commercial indirect composite resin (Sinfony, 3M/ESPE) after incorporation of single-wall carbon nanotubes (SWCNTs; Sigma-Aldrich, Inc., St. Louis, Missouri, United States) with or without the silanization form. Specimens of composite resin were fabricated in a Teflon mold. The composite resin was prepared according to the manufacturer's instructions (n = 10 for each group), with SWCNTs in three concentrations. The SWCNTs and SWCNT/SiO2-ATES specimens were evaluated by transmission electron microscopy, and a flexural test was conducted according to the ISO 4049/2009. Flexural strength data in MPa were submitted to one-way ANOVA following Tukey (p < 0.05). The SWCNTs did not improve the flexural strength of indirect composite resin when compared with the control, independent of the concentration added (p > 0.05). However, when SWCNTs and SWCNTs/SiO2-ATES were compared, the SWCNTs/SiO2-ATES showed higher values than the three concentrations of SWCNTs (p < 0.05). The silanization process improves the SWCNTs strength proprieties, but the modification of chemical bonding between SWCNT and SWCNT/SiO2-ATES modified resins, in different concentrations, did not improve the composite resin flexural strength.

Silanized graphene oxide as a reinforcing agent for acrylic bone cements: physicochemical, mechanical and biological characterization

Recently, different carbon-based nanomaterials have been used as reinforcing agents in acrylic bone cement formulations. Among them, graphene oxide (GO) has attracted the attention of scientific community since it could improve not only the mechanical properties but also the biocompatibility characteristics of these materials. However, using GO presents some drawbacks, such as its poor dispersion and lack of interaction with polymeric matrices, which should be prior resolved to achieve its optimal performance in acrylic bone cement. Thus, in this work, GO was treated with 3-methacryloxy propyl trimethoxy silane at various concentrations (1, 3 and 5 wt.%) to improve the interaction between the nanofiller and the poly (methyl methacrylate) matrix. Modified GO was incorporated at different percentages (0.1, 0.5 and 0.75 wt.%) into acrylic bone cement formulations and some properties were evaluated. The silanization process of the GO was confirmed by FTIR, TGA and EDX. The improvement in the mechanical performance was monitored on the compression properties whereas those related with biological properties were evaluated by osteoblast cell viability and hemocompatibility tests. Results suggest that using a 1 wt.% of the silane coupling agent, during surface treatment of GO, yields the best mechanical performance in this type of materials. It was also found that the presence of neat GO or silanized GO does not compromise the cytocompatibility and hemocompatibility of acrylic bone cement formulations.

Hydrophobic, moisture resistant and biorenewable paper coating derived from castor oil based epoxy methyl ricinoleate with repulpable potential

After ban on single-use plastics, completely bio-based coating on paper is in great demand to replace the plastics liner and other organic-inorganic hybrid coating. To resolve the issues like moisture, hydrophilicty and repulpability after use, a green, sustainable and hydrophobic bio-coating material for paper substrate has been developed. In this work, silanized castor oil (SCO) and silanized methyl ricinoleate (SMR) bio-resins are synthesized by structural modifications of epoxidized castor oil through transesterification and silanization process, Subsequently, the silylated bio-resins are hydrolysed and subjected to crosslinking with cellulosic paper substrate through condensation process. The coated papers showed hydrophobicity with water contact angle (WCA) up to 97° and strongly moisture resistant (moisture content of 2–3%) nature. Scanning electron microscopy analysis with energy dispersive X-ray spectra confirms the uniform coating of SMR resin with better texture and higher degree of silane grafting. The water vapor transmission rate (WVTR) decreased by 77.5% after coating because of blockage of pores and strong bonding with the cellulosic fibers. Further the coated papers showed adequate thermal stability and better tensile strength for commercial packaging. These coatings are removed by exposing to strong alkali solution at 90 °C and the recyclability potential of the paper is confirmed for reuse. These renewable resourced and eco-friendly coating materials are found to be suitable alternative for paper packaging and other coating applications with circular economy approach.

Nanocomposites obtained by incorporation of silanized silver nanowires to improve mechanical properties and prevent fungal adhesion

AbstractIn this work, the surfaces of silver nanowires (AgNWs) were modified by silanization process to improve the mechanical and antibiofilm properties of polymethylmethacrylate (PMMA) dental resins. A two‐route methodology was used to silanize the AgNWs: first, a surface treatment using tetraethyl orthosilicate (TEOS) was performed to act as interface agent; and then, γ‐methacryloxypropyltrimethoxysilane (MPS) was used to insert functional groups compatible to the acrylic resin. PMMA/AgNWs composites were obtained using pristine (AgNWP) and modified AgNWs (AgNWM) at concentrations of 0.5 and 1.0 wt%. The mechanical (flexural and impact strength) and antibiofilm properties against Candida albicans was investigated. AgNWM showed an enhancement in the dispersion and adhesion within the PMMA matrix, which were responsible for improvements in the mechanical properties. Results of flexural strength showed significant improvements for the sample with incorporation of 0.5 wt% of AgNWM and no significative changes for the sample with AgNWP. In addition, a reduction of about 50% in the biofilm formation by C. albicans was observed for the samples with 0.5 and 1.0 wt% of AgNWM. The incorporation of silanized‐AgNWs into PMMA dental resins can combine improvements in antimicrobial activity and in the flexural strength, being a potential antimicrobial biomaterial for dental applications.

Biobased Polyurethane Composite Foams Reinforced with Plum Stones and Silanized Plum Stones.

In the following study, ground plum stones and silanized ground plum stones were used as natural fillers for novel polyurethane (PUR) composite foams. The impact of 1, 2, and 5 wt.% of fillers on the cellular structure, foaming parameters, and mechanical, thermomechanical, and thermal properties of produced foams were assessed. The results showed that the silanization process leads to acquiring fillers with a smoother surface compared to unmodified filler. The results also showed that the morphology of the obtained materials is affected by the type and content of filler. Moreover, the modified PUR foams showed improved properties. For example, compared with the reference foam (PUR_REF), the foam with the addition of 1 wt.% of unmodified plum filler showed better mechanical properties, such as higher compressive strength (~8% improvement) and better flexural strength (~6% improvement). The addition of silanized plum filler improved the thermal stability and hydrophobic character of PUR foams. This work shows the relationship between the mechanical, thermal, and application properties of the obtained PUR composites depending on the modification of the filler used during synthesis.

High hydrophobic poly(lactic acid) foams impregnating one-step Si–F modified lignin nanoparticles for oil/organic solvents absorption

In this work, the hydrophobic lignin nanoparticles (LNP) were synthesized by a synchronous modification of silanization and fluorination process. Thermogravimetric analyser, fourier-transform-infrared-spectroscopy, X-ray photoelectron spectroscopy and transmission electron microscopy were used to confirm the surface modified LNP (m-LNP). The maximum degradation temperature of m-LNP was 85 °C higher than that of origin LNP. Then the bio-based PLA foams were prepared via freezing-dry method by impregnating various amount of m-LNP. The results showed that a high hydrophobicity (141° of contact angle) and porosity structure (94% of porosity) were constructed when the m-LNP content increased to 6 wt% (PLA-6L). Afterwards, the absorption capacities of the PLA composite foams towards various oil/organic solvents are measured. The composite foams reached their saturated adsorption capacity in quite short time and exhibited good recyclability due to the two factors: high hydrophobicity and high porosity. Thus, the bio-based PLA/m-LNP composite foams could be used as the eco-benign and efficient absorbents for petroleum leakage, oil spills and toxic organic solvents in water contamination field.

Antibacterial effect of titanium dioxide-doped phosphate glass microspheres filled total-etch dental adhesive on S. mutans biofilm

Abstract Purpose to improve the antibacterial action of a two-step total-etch dental adhesive by using titanium dioxide-doped phosphate glass microspheres (GMs) without affecting its penetration ability. Materials and methods Five and 10 wt% of APTES silanized [surface treated with 3-Aminopropyltriethoxysilane (APTES)] and non-silanized GMs have been used as a filler to Adper™ Single Bond 2 Refill. The morphology, chemistry and ζ - potential of GMs have been investigated using scanning electron microscopy, Fourier transform infra-red (FTIR) spectroscopy and Zeta-sizer respectively. The chemistry and antibacterial action of filled adhesive have been investigated using FTIR and nitrocellulose filter membranes (NFM) S. mutans biofilm model respectively. The number of colony forming units (CFU) per NFM was considered. The contact angle and microtensile bond strength of adhesives to mid-coronal dentin, as a measure of its penetration ability, have been investigated using a Drop Shape Analyzer and microtensile testing machine respectively. Adper™ Single Bond 2 Refill was used as a control. Results The size of GMs varied from 60 to 200 μm. The silanization process was confirmed by reduction in ζ-potential [-7 (±2) mV] and the presence of amide (1500-1600 cm−1), C–N (1380 cm−1), Si–O–Si (1096 cm−1) and Si–O–C (780 cm−1) peaks. Incorporation of GMs had no adverse effect on monomer conversion. All tested adhesives including the control showed significantly higher antibacterial action (~5–7 log10 reduction in CFU) than the NFM control. All filled adhesives showed significantly higher antibacterial action (~1–2 log10 reduction in CFU) than the control adhesive. The non-silanized GMs filled adhesives showed the highest antibacterial action against S. mutans biofilm formation. The presence of silanized GMs did not affect the wetting but increased the microtensile bond strength of the adhesive to dentin. Conclusion Glass microsphere modified adhesives could be promising to reduce the possibility of recurrent caries around restorations.

Beneficial effect of pre-oxidization process on the formation of silane films on iron

Silanization has been recognized as a novel and green pretreatment process of metals in the past decades. However, due to the difficulty of film formation, silanization technique has not yet been applied in industrial scale to carbon steels. In this paper pre-oxidation technique was employed in order to intentionally solve this problem. Both the chemical pre-oxidation and anodic pre-oxidation were found to benefit the formation of ferric hydroxide (FeOOH), and thereby facilitate the subsequent silanization process. The effect of hydroxylation of iron substrate on the adsorption kinetics of silane molecule was then theoretically illustrated by using molecular dynamics simulation. • Pre-oxidation of iron produces larger number of hydroxylated groups. • The improved number of hydroxylated groups facilitates the formation of silane films on iron substrate. • Molecular dynamic simulation is used to interpret the easier adsorption of silane molecule on the surface of FeOOH than on Fe.

Porosity-induced mechanically robust superhydrophobicity by the sintering and silanization of hydrophilic porous diatomaceous earth

HypothesisBecause they have self-similar low-surface-energy microstructures throughout the whole material block, fabricating superhydrophobic monoliths has been currently a promising remedy for the mechanical robustness of non-wetting properties. Noticeably, porous materials have microstructured interfaces throughout the complete volume, and silanization can make surfaces low-surface-energy. Therefore, the porous structure and surface silane-treatment can be combined to render hydrophilic inorganics into mechanically durable superhydrophobic monoliths. ExperimentsSuperhydrophobic diatomaceous earth pellets were produced by thermal-sintering, followed by a silanization process with octyltriethoxysilane. The durability of superhydrophobicity was evaluated by changes in wetting properties, surface morphology, and chemistry after a systematic abrasion sliding test. FindingsThe intrinsic porosity of diatomite facilitated surface silanization throughout the whole sintered pellet, thus producing the water-repelling monolith. The abrasion sliding converted multimodal porosity of the volume to hierarchical roughness of the surface comprised of silanized particles, thereby attaining superhydrophobic properties of high contact angles over 150° and sliding angles below 20°. The tribological properties revealed useful information about the superhydrophobicity duration of the non-wetting monolith against friction. The result enables the application of porous structures in the fabrication of the anti-abrasion superhydrophobic materials even though they are originally hydrophilic.

The simulation of droplet impact on the super-hydrophobic surface with micro-pillar arrays fabricated by laser irradiation and silanization processes

Super-hydrophobicity is one of the significant natural phenomena, which has inspired researchers to fabricate artificial smart materials using advanced manufacturing techniques. In this study, a super-hydrophobic aluminum surface was prepared by nanosecond laser texturing and FAS modification in sequence. The surface wettability turned from original hydrophilicity to super-hydrophilicity immediately after laser treatment. Then it changed to super-hydrophobicity showing a WCA of 157.6 ± 1.2° with a SA of 1.7 ± 0.7° when the laser-induced rough surface being coated with a layer of FAS molecules. The transforming mechanism was further explored from physical and chemical aspects based on the analyses of surface morphology and surface chemistry. Besides, the motion process of droplet impacting super-hydrophobic surface was systematically analyzed via the optimization of simulation calculation grid and the simulation method of volume of fluid (VOF). Based on this simulation method, the morphological changes, the inside pressure distribution and velocity of the droplet were further investigated. And the motion mechanism of the droplet on super-hydrophobic surface was clearly revealed in this paper. The simulation results and the images captured by high-speed camera were highly consistent, which indicated that the computational fluid dynamics (CFD) is an effective method to predict the droplet motion on super- hydrophobic surfaces. This paper can provide an explicit guidance for the selection of suitable methods for functional surfaces with different requirements in the industry.

Process synthesis and optimization of SiO2/PVDF mixed-matrix membrane for oil-water emulsion separation

In this study, and optimized silicon oxide (SiO2)/polyvinyledene fluoride (PVDF) mixed-matrix membrane formulation was developed using response surface methodology (RSM). SiO2 nanoparticles (NPs) concentration (1-3%), silane solution concentration (1:100-3:100 ratio of silane to ethanol) and duration of silanization process (240-600 s) were identified as the factor in affecting the membrane performance, both permeate flux and rejection. The synthesized membranes were characterized in terms of membrane pore size, porosity, surface roughness, and surface wettability. The optimum SiO2/PVDF mixed-matrix membrane formulation was obtained with 2.9% SiO2 NPs concentration, 2.22:100 ratio of silane to ethanol, with 496 seconds of salination process duration. The optimum SiO2/PVDF mixed-matrix membrane formulation exhibited an extraordinarily high oil droplets rejection (92.01%) with 27.57 L/m2 h of permeate flux at 1 bar of operating pressure.

Temperature-dependent wetting characteristics of micro–nano-structured metal surface formed by femtosecond laser

The hydrophilicity induced by micro–nano-structured surface has aroused great attention for promising applications. In this work, the temperature-dependent surface wettability with different micro–nano-structures prepared by femtosecond lasers is studied systematically. It is found that the contact angle of both the micro- and nano-structural hydrophilic surfaces reduces as the ambient temperature decreases from 60 to 20 °C, but the contact angles of the typical microscale surfaces increase when the surface temperature reduces from 20 to 5 °C when the surface temperature is lower than ambient temperature. Furthermore, it is found that some microscale structural samples show a much weaker temperature dependence than others, which is experimentally proved to be due to the strong capillary effects in those specific microscale structures. By contrast, hydrophobic micro–nano-structural samples with the same structure obtained by silanization process always show that the hydrophobicity of both nano- and micro-structured surfaces decreases when temperature decreases from 20 to 5 °C. To the best of our knowledge, we are the first to report the temperature-dependent wettability of hydrophilic micro–nano-structured surfaces with surface temperature below ambient temperature. The findings in this work can be applied to the micro- and nanoscale structural surface formed by other methods, and it will be beneficial to the engineering design and manufacture of micro–nano-structured surfaces to achieve the desired performance of the wetting function, which is of great significance to the application of hydrophilic micro–nano-structured surfaces in varied temperature surroundings.

Self-Assembled Monolayers Assisted all Wet Metallization of SU-8 Negative Tone Photoresist

The present work investigates the application of a Self-Assembled Monolayer (SAM) on the widely used negative photoresist SU-8. (3-Aminopropyl) trimethoxysilane (APTMS) is employed to form SAMs on the surface of the polymer through wet silanization in ethanol. The treatment process of SU-8 resin surface is optimized to achieve a well-formed, high quality SAM. Wettability measurements, atomic force microscopy (AFM) and infrared (IR) spectroscopy are employed to follow and optimize the silanization process. Following silanization, the resulting SAMs are employed as adhesion layers for electroless plated metallic layers. For this purpose, the superior affinity of APTMS amine terminal groups towards Pd2+ ions is exploited to activate the surface. Metallic coatings such as Cu, Ni–P or Co–Ni–P are thus deposited by mean of autocatalytic deposition. The surface of metallized samples is analyzed using AFM, scanning electron microscopy (SEM) and glow discharge optical emission spectroscopy (GDOES). Finally, Ni–P is deposited on a micropatterned SU-8 surface to demonstrate the potential of the presented metallization approach for microfabrication.

Influence of the addition of multi‐walled carbon nanotubes on the thermal and mechanical properties of polyamide‐11 before and after aging tests

AbstractIn this work, the preparation and characterization of nanocomposites of commercial polyamide‐11 reinforced with multi‐walled carbon nanotubes (MWCNT), untreated, oxidized or with the modified surface through silanization with 3‐aminopropyl trimethoxy silane (APTMS), in concentrations of 0.1%, 0.5%, and 1.0 wt% in the polymer matrix was investigated. The processing of the nanocomposites was carried out via mixing in the molten state in a twin‐screw mini‐extruder at 200°C under 60 rpm screw rotation speed, with a residence time of 7 min. The addition of the MWCNT increased the thermal stability of PA11, predominantly with 0.5% of silanized nanotubes, as observed by the thermogravimetric analysis. X‐ray diffraction and differential scanning calorimetry analyses indicated that the degree of crystallinity of the formulations increased with the nanofiller content. On the other hand, the use of the highest concentration generated agglomerates, suggesting less dispersion in the matrix and, consequently, a reduction in crystallinity. Dynamic mechanical thermal analysis showed that the silanization process promoted an increase in both loss and storage moduli. All produced nanocomposites obtained values of corrected inherent viscosity above 1.20 dl/g, before and after the aging test. The use of lower load levels promoted better processability due to the lubricating effect of the nanotubes and an increase in the hydrophobic character of the samples, as observed by the increase of the contact angle.

Thiourethane filler functionalization for dental resin composites: Concentration-dependent effects on toughening, stress reduction and depth of cure

ObjectivesThe aim of this study was to modify the surface of fillers used in dental composites by the synthesis of two novel thiourethane oligomeric silanes, used to functionalize the silica-containing inorganic particles. Several thiourethane silane concentrations were tested during the silanization process to systematically assess the effect of silane coverage on experimental composite conversion, polymerization stress and fracture toughness. Materials and methodsTwo different thiourethane silanes were synthesized based either on 1,6-hexanediol-diissocynate (HDDI), or 1,3-bis(1-isocyanato-1-methylethyl) benzene (BDI). Conventional 3-(Trimethoxysilyl)propyl methacrylate was used as the control. Glass fillers were silanized with 1, 2 or 4 wt% of each thiourethane silane, then evaluated by thermogravimetrical analysis. Photopolymerizable resin composites were prepared with Bis-GMA/UDMA/TEGDMA and 50 wt% silanized glass filler. Polymerization kinetics and degree of conversion were tested using Near-IR. Bioman was used to test polymerization stress. Data were analyzed with two-way ANOVA/Tukey's test (α = 5%). ResultsThe mass of silane coupled to the filler increased with the concentrations of thiourethane in the silanizing solution, as expected. Thiourethane-containing groups exhibited significantly higher degree of conversion compared to control groups, except for BDI 4%. HDDI 4%, BDI 2% and BDI 4% showed significantly lower polymerization stress than control groups. HDDI 4% exhibited significantly higher fracture toughness. Conclusions and clinical significanceNovel filler functionalization with thiourethane silanes may be a promising alternative for improving dental composites properties by significantly increasing the degree of conversion, fracture toughness and reducing the polymerization stress.

Microfluidic fluorescence immunosensor using ZnONFs for invasive aspergillosis determination

Galactomannan (GM) is a polysaccharide cell-wall component released by Aspergillus species, used as a biological marker for invasive aspergillosis (IA) screening. A fluorescence microfluidic immunosensor for GM detection was developed by using ZnO nanoflowers (ZnONFs) synthesized by a wet chemical method and characterized by scanning electron microscopy and energy dispersive spectrometry. The ZnONFs were covalently linked to the microfluidic channel through a silanization process with 3-aminopropyl triethoxysilane and then used as a bioaffinity nanoplatform for the immobilization of monoclonal anti-GM antibodies, which react specifically with the GM present in human serum samples.Subsequently, the GM amount that reacted was quantified by an HRP-anti-GM antibody (type sandwich immunoassay), which in the presence of H2O2 catalyzes the oxidation of 10-acetyl-3,7-dihydroxyphenoxacine to a highly fluorescent resorufin, which was measured by a laser-induced fluorescence (LIF) detector (excitation at 561 nm and emission at 585 nm).The measured fluorescence is directly proportional to the concentration of GM present in the patient serum sample. The fluorescence method was compared with a previously published electrochemical method, and a commercial ELISA test, showing outstanding properties. This immunosensor can be applied to the IA early diagnosis since it offers several attractive advantages such as high selectivity and sensitivity.

Improvement of mechanical and physical performance of poly (lactic acid) biocomposites by application of surface silanization for huntite–hydromagnesite mineral

Silanization process was applied to huntite–hydromagnesite (HH) mineral in for improve its adhesion to poly (lactic acid) (PLA) matrix. Surfaces of HH samples were examined by infrared spectroscopy and energy-dispersive X-ray spectroscopy analysis. HH was compounded with PLA using melt-blending technique. Modified HH incorporations led to nearly 19% and 20% increase in tensile strength and modulus of PLA, respectively. The maximum improvement for tensile strength value is obtained for 15 wt% of modified HH containing composite sample. On the other hand, percentage strain of PLA decreases nearly 22% with the addition of HH. Silane-modified HH-containing composites yield higher impact energy compared to untreated HH. Impact performance of composites increases nearly 18% with the increase in loading ratio of HH. Silane-modified HH displays higher storage modulus than HH, and glass transition temperature of PLA shifts to higher levels with the inclusion of HH. HH-filled composites exhibit no significant difference with melt flow rate value of PLA. Water resistance of silane-treated HH-containing composites are found to be higher than untreated HH attribitued to hydrophobicity of silicon-rich surface. Accordingly, composites that include modified HH are suitable for outdoor applications. Morphological investigations confirm that dispersion homogeneity and strong adhesion are achieved due to the improvement of surface interactions between HH and PLA phases after silane treatment process.

Role of the chemical modification of titanium dioxide surface on the interaction with silver nanoparticles and the capability to enhance antimicrobial properties of poly(lactic acid) composites

In this work, the antimicrobial activity of neat and silanized titanium dioxide deposited with silver nanoparticles was evaluated when it was used as filler in a poly(lactic acid) matrix. The silanization and deposition processes were evaluated by scanning transmission electron microscopy and X-ray photoelectron spectroscopy confirming the chemical modification on the titanium dioxide surface by 3-aminopropyltriethoxy silane and the formation of silver nanoparticles. According to the elemental analysis conducted by energy-dispersive X-ray spectroscopy, more silver, 7.4% higher, was deposited on the oxide when this was previously silanized and when 30% w/w of silver nitrate was used as a precursor. The antimicrobial effect was confirmed for the nanoparticles through the disk diffusion method and for the composites by drop test, against Staphylococcus aureus and Escherichia coli bacteria; the results showed that the inhibition rate increased by 14.2% and 39.1% for nanoparticles and by 57.6% and 38.8% for composites against each bacteria, respectively, when deposition was performed on silanized titanium dioxide. Also, better mechanical properties were obtained in the composites filled with silanized oxide; the best results were obtained in the PLA/sTiO2–Ag 20% system with an improvement of 45.7% in tensile stress and of 38.73% for Young’s modulus. Finally, the toxicity of the composites was evaluated by seeding peripheral blood mononuclear cells; results show evidence that composites filled with these nanoparticles are non-toxic since these do not migrate from the polymeric matrix, which helps to enhance the prolonged surface antibacterial effect and to open a broad perspective of the commercial use of these composites.