Injectable Thermosensitive Nanocomposites Based on Poly(N-vinylcaprolactam) and Silica Particles for Localized Release of Hydrophilic and Hydrophobic Drugs.

The systemic delivery of drugs employed by conventional methods has shown to be less effective than a localized delivery system. Many drugs have the effectiveness reduced by fast clearance, increasing the amount required for an efficient treatment. One way to overcome this drawback is through the use of thermoresponsive polymers that undergo a sol-gel transition at physiological temperature, allowing their injection directly in the desired site. In this work, thermosensitive nanocomposites based on poly(N-vinylcaprolactam) and silica particles with 80 and 330 nm were synthesized to be employed as delivery systems for hydrophobic (naringin) and hydrophilic (doxorubicin hydrochloride) drugs. The insertion of SiO2 increased the rheological properties of the nanocomposite at 37 °C, which helps to prevent its diffusion away from the site of injection. The synthesized materials were also able to control the drug release for a period of 7 days under physiological conditions. Due to its higher hydrophobicity and better interaction with the PNVCL matrix, naringin presented a more controlled release. The Korsmeyer-Peppas model indicated different release mechanisms for each drug. At last, a preliminary in vitro study of DOX-loaded nanocomposites cultured with L929 and MB49 cells showed negligible toxic effects on healthy cells and better efficient inhibition of carcinoma cells.

Probing the Structural Dynamics of the Coil-Globule Transition of Thermosensitive Nanocomposite Hydrogels.

Nanocomposite hydrogels have emerged to exhibit multipurpose properties, boosting especially the biomaterial field. However, the development and characterization of these materials can be a challenge, especially stimuli-sensitive materials with dynamic properties in response to external stimuli. By employing UV-vis spectroscopy and NMR relaxation techniques, we could outline the formation and behavior of thermosensitive nanocomposites obtained by in situ polymerization of poly(N-vinylcaprolactam) (PNVCL) and mesoporous silica nanofibers under temperature stimuli. For instance, inorganic nanoparticles covalently linked to PNVCL changed the pattern of temperature-induced phase transition despite showing similar critical temperatures to neat PNVCL. Thermodynamic parameters indicated the formation of an interconnected system of silica and polymer chains with reduced enthalpic contribution and mobility. The investigation of water molecule and polymer segment motions also revealed that the absorption and release of water happened in a wider temperature range for the nanocomposites, and the polymer segments respond in different ways during the phase transition in the presence of silica. This set of techniques was essential to reveal the polymer motions and structural features in nanocomposite hydrogels under temperature stimuli, demonstrating its potential use as experimental guideline to study multicomponent nanocomposites with diverse functionalities and dynamic properties.

Analyzing the Effects of Silica Nanospheres on the Sol-Gel Transition Profile of Thermosensitive Hydrogels.

The insertion of nanoparticles into smart hydrogels can diversify their functionalities by a synergistic combination of the components properties within the hydrogels. While these hybrid systems are attractive to the biomaterials field, careful design and control of their properties are required since the new interactions between the polymer and the nanoparticles can result in changes or the loss of hydrogels stimuli response. In order to understand the physicochemical aspects of the thermoresponsive systems, nanocomposites of poly(N-vinylcaprolactam) (PNVCL) and silica nanoparticles with different sizes and concentrations were synthesized. The UV-vis and DLS techniques showed that the PNVCL has a sharp phase transition at 34 °C, while the nanocomposites have a diffuse transition. The nanocomposites showed an initial coil-globule transition before the phase transition takes place. This was identified by the evolution of the hydrodynamic diameter of the nanocomposite globules before the cloud point temperature (Tcp), which remained constant for PNVCL. This new transition profile can be described by two stages in which microscopic volume transitions occur first, followed by the macroscopic transition that forms the hydrogel. These results show that the proposed nanocomposites can be designed to have tunable stimuli response to smaller temperature variations with the formation of intermediate globule states.

Effect of Fluoride Toothpaste Containing Nano-Sized Sodium Hexametaphosphate on Enamel Remineralization: An in situ Study.

OBJECTIVE: To evaluate the remineralizing potential of a conventional toothpaste (1,100 ppm F) supplemented with nano-sized sodium hexametaphosphate (HMPnano) in artificial caries lesions in situ. DESIGN: This double-blinded crossed study was performed in 4 phases of 3 days each. Twelve subjects used palatal appliances containing 4 bovine enamel blocks with artificial caries lesions. Volunteers were randomly assigned into the following treatment groups: no F/HMP/HMPnano (Placebo); 1,100 ppm F (1100F); 1100F plus 0.5% micrometric HMP (1100F/HMP) and 1100F plus 0.5% nano-sized HMP (1100F/HMPnano). Volunteers were instructed to brush their natural teeth with the palatal appliances in the mouth for 1 min (3 times/day), so that blocks were treated with natural slurries of toothpastes. After each phase, surface hardness post-remineralization (SH2), integrated recovery of subsurface hardness (ΔIHR), integrated mineral recovery (ΔIMR) and enamel F concentration were determined. Data were submitted to analysis of variance and Student-Newman-Keuls' test (p < 0.001). RESULTS: Enamel surface became 42% harder when treated with 1100F/HMPnano in comparison with 1100F (p < 0.001). Treatment with 1100F/HMP and 1100F/HMPnano promoted an increase of ∼23 and ∼87%, respectively, in ΔIHR when compared to 1100F (p < 0.001). In addition, ΔIMR for the 1100F/HMPnano was ∼75 and ∼33% higher when compared to 1100F and 1100F/HMP respectively (p < 0.001). Enamel F uptake was similar among all groups except for the placebo (p < 0.001). CONCLUSION: The addition of 0.5% HMPnano to a conventional fluoride toothpaste was able to promote an additional remineralizing effect of artificial caries lesions.

Kinetic Control of Microtubule Morphology Obtained by Assembling Gold Nanoparticles on Living Fungal Biotemplates.

Self-assembly of nanoparticles on living biotemplate surfaces is a promising route to fabricate nano- or microstructured materials with high efficiency and efficacy. We used filamentous fungi to fabricate microtubules of gold nanoparticles through a novel approach that consists of isolating the hyphal growth from the nanoparticle media. This improved methodology resulted in better morphological control and faster adsorption kinetics, which reduced the time needed to form homogeneous microtubules and allowed for control of microtubule thickness through successive additions of nanoparticles. Differences in the adsorption rates due to modifications in the chemical identity of colloidal gold nanoparticles indicated the influence of secondary metabolites and growth media in the fungi metabolism, which demonstrated the need to choose not only the fungus biotemplate but also the correct medium to obtain microtubules with superior properties.

The effect of silver nanoparticles and nystatin on mixed biofilms of Candida glabrata and Candida albicans on acrylic.

The aim of this study was to compare biofilm formation by Candida glabrata and Candida albicans on acrylic, either individually or when combined (single and dual species) and then examine the antimicrobial effects of silver nanoparticles and nystatin on these biofilms. Candidal adhesion and biofilm assays were performed on acrylic surface in the presence of artificial saliva (AS) for 2 h and 48 h, respectively. Candida glabrata and C. albicans adherence was determined by the number of colony forming units (CFUs) recovered from the biofilms on CHROMagar(®) Candida. In addition, crystal violet (CV) staining was used as an indicator of biofilm biomass and to quantify biofilm formation ability. Pre-formed biofilms were treated either with silver nanoparticles or nystatin and the effect of these agents on the biofilms was evaluated after 24 h. Results showed that both species adhered to and formed biofilms on acrylic surfaces. A significantly (P < 0.05) higher number of CFUs was evident in C. glabrata biofilms compared with those formed by C. albicans. Comparing single and dual species biofilms, equivalent CFU numbers were evident for the individual species. Both silver nanoparticles and nystatin reduced biofilm biomass and the CFUs of single and dual species biofilms (P < 0.05). Silver nanoparticles had a significantly (P < 0.05) greater effect on reducing C. glabrata biofilm biomass compared with C. albicans. Similarly, nystatin was more effective in reducing the number of CFUs of dual species biofilms compared with those of single species (P < 0.05). In summary, C. glabrata and C. albicans can co-exist in biofilms without apparent antagonism, and both silver nanoparticles and nystatin exhibit inhibitory effects on biofilms of these species.

Antifungal activity of silver nanoparticles in combination with nystatin and chlorhexidine digluconate against Candida albicans and Candida glabrata biofilms.

Although silver nanoparticles (SN) have been investigated as an alternative to conventional antifungal drugs in the control of Candida-associated denture stomatitis, the antifungal activity of SN in combination with antifungal drugs against Candida biofilms remains unknown. Therefore, the aim of this study was to evaluate the antifungal efficacy of SN in combination with nystatin (NYT) or chlorhexidine digluconate (CHG) against Candida albicans and Candida glabrata biofilms. The drugs alone or combined with SN were applied on mature Candida biofilms (48 h), and after 24 h of treatment their antibiofilm activities were assessed by total biomass quantification (by crystal violet staining) and colony forming units enumeration. The structure of Candida biofilms was analysed by scanning electron microscopy (SEM) images. The data indicated that SN combined with either NYT or CHG demonstrated synergistic antibiofilm activity, and this activity was dependent on the species and on the drug concentrations used. SEM images showed that some drug combinations were able to disrupt Candida biofilms. The results of this study suggest that the combination of SN with NYT or CHG may have clinical implications in the treatment of denture stomatitis. However, further studies are needed before recommending the use of these drugs safely in clinical situations.

Chitosan-based sponges containing clotrimazole for the topical management of vulvovaginal candidiasis.

Vulvovaginal candidiasis (VVC) persists as a worrying women's healthcare issue, often relying on suboptimal therapeutics. Novel intravaginal dosage forms focusing on improving patient acceptability and featuring improved biopharmaceutical properties could be interesting alternatives to available antifungal products. Different formulations of sponges based on chitosan (Ch), with or without crosslinking and co-formulated with poly(N-vinylcaprolactam) (PNVCL), were produced for the topical administration of clotrimazole (CTZ) and further tested for physicochemical properties, drug release, cytotoxicity and antifungal activity. Results showed that high amounts of CTZ (roughly 30-50 %) could be incorporated into sponges obtained by using a simple freeze-drying methodology. Cross-linking of Ch with ammonia affected the morphology and mechanical features of sponges and shifted the release profile from sustained (around 20 % and 60 % drug released after 4 h and 24 h, respectively) to fast-releasing (over 90 % at 4 h). The combination of PNVCL with non-crosslinked Ch also allowed tuning drug release, namely by increasing the initial amount of CTZ released in simulated vaginal fluid (roughly 40 % after 4 h), as compared to sponges featuring only non-crosslinked Ch. All formulations displayed low toxicity to cell lines derived from the female genital tract, with viability values kept above 70 % after 24 h incubation with sponge extracts. These also allowed maintaining the rapid onset of the antifungal effects of CTZ at minimum inhibitory concentrations ranging from 0.5 to 16 µg/mL for a panel of six different Candida spp. strains. Overall, proposed sponge formulations appear to be promising alternatives for the safe and effective management of VVC.

Assembly and antifungal effect of a new fluconazole-carrier nanosystem.

Aim: To assemble, characterize and assess the antifungal effects of a new fluconazole (FLZ)-carrier nanosystem. Materials & methods: The nanosystem was prepared by loading FLZ on chitosan (CS)-coated iron oxide nanoparticles (IONPs). Antifungal effects were evaluated on planktonic cells (by minimum inhibitory concentration determination) and on biofilms (by quantification of cultivable cells, total biomass, metabolism and extracellular matrix) of Candida albicans and Candida glabrata. Results: Characterization results ratified the formation of a nanosystem (<320 nm) with FLZ successfully embedded. IONPs-CS-FLZ nanosystem reduced minimum inhibitory concentration values and, in general, showed similar antibiofilm effects compared with FLZ alone. Conclusion: IONPs-CS-FLZ nanosystem was more effective than FLZ mainly in inhibiting Candida planktonic cells. This nanocarrier has potential to fight fungal infections.

Phase transformation in titania nanocrystals by the oriented attachment mechanism: the role of the pH value.

The oriented attachment (OA) mechanism has been investigated as an important process in the formation of anisotropic nanostructures such as depicted. The results showed that the control of a desired phase in this system may be attained by the control of OA mechanism through pH value, obtaining several morphologies.A new synthetic method for TiO(2) nanocrystals starting from metallic Ti and hydrogen peroxide was developed, in order to obtain minimal interferences to evaluate phase transformation in the system. The results revealed that the crystal morphology appeared to be dictated by the pH value, which shows a strong dependence on the surface energy. The involvement of the oriented attachment (OA) mechanism is important to modify the morphology and, hence, the distribution of the surface energy and confirmed that the mechanism can accelerate certain phase transitions, albeit pH dependence in terms of how the mechanism affects the final particle morphology and direction of crystalline growth. The importance of the mechanism was also apparent in extremely basic conditions, which indicates a possible correlation with the formation of hydrogen titanate nanostructures.

Antimony-doped tin oxide nanocrystals: synthesis and solubility behavior in organic solvents.

This work focuses on the nonaqueous synthesis of antimony-doped tin oxide nanocrystals in the size range of 2-6 nm and the investigation of their solubility in organic solvents (CHCl(3) and THF) in the presence of amphiphilic molecules (oleic acid and oleylamine). To unravel the underlying processes, a set of molecular dynamics simulations is performed involving the compatibility of oleic acid and oleylamine in mixtures with both CHCl(3) and THF. The results show that the method is useful for obtaining the desired oxide, and that the interaction between amphiphilic molecules and solvents can be predicted by molecular dynamics simulations with very good qualitative agreement.

Green synthesis of silver nanoparticles combined to calcium glycerophosphate: antimicrobial and antibiofilm activities.

AIM: To synthesize, characterize and evaluate the antimicrobial and antibiofilm activities of novel nanocomposites containing silver nanoparticles (AgNPs) associated or not to ß-calcium glycerophosphate. MATERIALS & METHODS: These nanocomposites were produced through a 'green' route using extracts of different parts of pomegranate. Antimicrobial and antibiofilm properties against Candida albicans and Streptococcus mutans were determined by the minimum bactericidal/fungicidal concentration and biofilm density after treatments. RESULTS: All extracts used were successful in producing AgNPs. Composites made with peel extracts showed the highest antimicrobial and antibiofilm activity against both microorganisms tested and performed similarly or even better than chlorhexidine. CONCLUSION: AgNPs associated or not to calcium glycerophosphate produced by a 'green' process may be a promising novel antimicrobial agent against oral microorganisms.

* Thermosensitive Poly(N-vinylcaprolactam) Injectable Hydrogels for Cartilage Tissue Engineering.

Injectable hydrogels have gained prominence in the field of tissue engineering for minimally invasive delivery of cells for tissue repair and in the filling of irregular defects. However, many injectable hydrogels exhibit long gelation times or are not stable for long periods after injection. To address these concerns, we used thermosensitive poly(N-vinylcaprolactam) (PNVCL) hydrogels due to their cytocompatibility and fast response to temperature stimuli. Changes in the PNVCL molecular weight and concentration enabled the development of hydrogels with tunable mechanical properties and fast gelation times (<60 s when the temperature was raised from room temperature to physiologic temperature). Chondrocytes (CHs) and mesenchymal stem cells were encapsulated in PNVCL hydrogels and exhibited high viability (∼90%), as monitored by Live/Dead staining and Alamar Blue assays. Three-dimensional constructs of CH-laden PNVCL hydrogels supported cartilage-specific extracellular matrix production both in vitro and after subcutaneous injection in nude rats for up to 8 weeks. Moreover, biochemical analyses of constructs demonstrated a time-dependent increase in glycosaminoglycans (GAGs) and collagen, which were significantly augmented in the implants cultured in vivo. Histological analyses also demonstrated regular distribution of synthesized cartilage components, including abundant GAGs and type II collagen. The findings from this study demonstrate thermosensitive PNVCL as a candidate injectable biomaterial to deliver cells for cartilage tissue engineering.

Dynamic and structural correlations in nanocomposites of silica with modified surface and carboxylated nitrile rubber.

Distinct affinities between the organic and inorganic phases were observed in nanocomposites prepared through a colloidal route with carboxylated nitrile rubber and modified silica nanoparticles, which resulted in variable mechanical properties and improved thermal stability. Nanoparticles with modified surface affected the macromolecular arrangements of the elastomeric matrix, changing the final mechanical behavior of the nanocomposite, which could be predicted by the spin-lattice relaxation time measured by solid-state NMR. It was also possible to identify how each different nanoparticle affected the molecular dynamic of nanocomposite, correlating the dynamic-mechanical analysis with the NMR data of the saturated carbons of the elastomer.

In vivo toxicity and antimicrobial activity of AuPt bimetallic nanoparticles

Despite the potential antimicrobial activity of metallic nanoparticles, the increasing concerns about nanosafety have been holding back the use of these materials in therapeutics and biomedical devices. In the last years, several studies called attention to metallic nanoparticles toxicity. In the most part of in vitro studies performed with mammalian cells, metallic NPs reduced cell viability and induced genotoxicity and inflammatory responses. Bimetallic NPs have attracted great attention because they present distinct and even more advanced characteristics when compared to nanoparticles formed by a single metal. Recently, bimetallic NPs have emerged as an alternative to improve the antimicrobial activity of metallic nanoparticles, aiming at the broadening of the action spectrum and the reduction of the toxicity. However, the biocompatibility of bimetallic nanoparticles has been demonstrated only by in vitro studies. In the present work, the toxicity of AuPt nanoparticles was addressed both in vitro and in vivo. In addition, the antimicrobial activity of AuPt bimetallic nanoparticles has been evaluated in comparison with Au and Ag nanoparticles. The nanoparticles were characterized by ultraviolet-visible spectroscopy, dynamic light scattering, transmission electron microscopy, inductively coupled plasma optical emission spectroscopy, and X-ray diffraction. The antimicrobial activity was studied against Candida albicans, Pseudomonas aeruginosa, and Staphylococcus aureus. The toxicity of nanoparticles was evaluated in vitro by analyzing their toxicity against human fibroblast cells (HS68 cell line) and in vivo by embryonic toxicity test in zebrafish (Danio rerio). The results confirmed the intrinsic antimicrobial activity of the three types of nanoparticles but different toxicity. Bimetallic nanoparticles showed enhanced antimicrobial activity in comparison with Au nanoparticles but lower antimicrobial activity compared with Ag nanoparticles. However, AuPt nanoparticles showed great advantage over Ag nanoparticles due to the absence of cytotoxicity and lower toxicity in vivo.

Synthesis and photocatalytic properties of bismuth titanate with different structures via oxidant peroxo method (OPM).

Bismuth titanate (Bi4Ti3O12 and Bi12TiO20) powders were synthesized by the Oxidant Peroxide Method (OPM), and the effect of temperatures on physical and chemical properties of particles was investigated. The results showed that the morphology and average particle size of materials can be successfully controlled by adjusting the temperature. The samples after calcination were characterized by X-ray diffractometry, transmission electron microscopy, diffuse reflectance spectroscopy, Raman spectroscopy, and BET isotherms. The photocatalytic activity of materials was also evaluated by studying the degradation of 10ppm aqueous rhodamine B dye under ultraviolet radiation.

In vivo toxicity and antimicrobial activity of AuPt bimetallic nanoparticles

Despite the potential antimicrobial activity of metallic nanoparticles, the increasing concerns about nanosafety have been holding back the use of these materials in therapeutics and biomedical devices. In the last years, several studies called attention to metallic nanoparticles toxicity. In the most part of in vitro studies performed with mammalian cells, metallic NPs reduced cell viability and induced genotoxicity and inflammatory responses. Bimetallic NPs have attracted great attention because they present distinct and even more advanced characteristics when compared to nanoparticles formed by a single metal. Recently, bimetallic NPs have emerged as an alternative to improve the antimicrobial activity of metallic nanoparticles, aiming at the broadening of the action spectrum and the reduction of the toxicity. However, the biocompatibility of bimetallic nanoparticles has been demonstrated only by in vitro studies. In the present work, the toxicity of AuPt nanoparticles was addressed both in vitro and in vivo. In addition, the antimicrobial activity of AuPt bimetallic nanoparticles has been evaluated in comparison with Au and Ag nanoparticles. The nanoparticles were characterized by ultraviolet-visible spectroscopy, dynamic light scattering, transmission electron microscopy, inductively coupled plasma optical emission spectroscopy, and X-ray diffraction. The antimicrobial activity was studied against Candida albicans, Pseudomonas aeruginosa, and Staphylococcus aureus. The toxicity of nanoparticles was evaluated in vitro by analyzing their toxicity against human fibroblast cells (HS68 cell line) and in vivo by embryonic toxicity test in zebrafish (Danio rerio). The results confirmed the intrinsic antimicrobial activity of the three types of nanoparticles but different toxicity. Bimetallic nanoparticles showed enhanced antimicrobial activity in comparison with Au nanoparticles but lower antimicrobial activity compared with Ag nanoparticles. However, AuPt nanoparticles showed great advantage over Ag nanoparticles due to the absence of cytotoxicity and lower toxicity in vivo.

Moderating effect of ammonia on particle growth and stability of quasi-monodisperse silver nanoparticles synthesized by the Turkevich method.

A new method to stabilize silver nanoparticles by the addition of ammonia is proposed. Colloidal dispersions of silver nanoparticles were synthesized by the Turkevich method using sodium citrate to reduce silver nitrate at high pH and at 90 °C. After approximately 12 min, a diluted ammonia solution was added to the reaction flask to form soluble diamine silver (I) complexes that played an important growth moderating role, making it possible to stabilize metallic silver nanoparticles with sizes as small as 1.6 nm after 17 min of reaction. Colloidal dispersions were characterized by UV-visible absorption spectroscopy, X-ray diffraction, and transmission electronic microscopy.