Scientific Production

In addition to developing applications for industry, nChemi team also conducts basic scientific research through interaction with research groups from different universities! Below our main published works.

The promising technologies to modify the future, demands materials with special properties. The functionalized nanocrystals represents the building blocks that can leverage these technologies. This project aims at the study of ZrO2 nanocrystals of oleic acid functionalized (AO) called NCf in dispersions in three different solvents, hexane, toluene and chloroform. In previous studies, it has been observed that the organic layer can modify the conformation of the molecules on the surface (the organic layer) depending on the solvent, the affinity allows it to swell, if it has high affinity or contracts, if the affinity is low. These studies were performed with transmission electron microscopy (TEM). However, the direct study in solutions is challenging due to the difficulty of the characterization of this system in relation to the nanometric size and the hybrid character of the nanomaterial. In order to overcome these difficulties, density and viscosity measurements of the NCf dispersions were used at concentrations. 1×10-3, 5×10-3, 1×10-2, 5×10-2 and 1×10-1 in triplicate. The nucleus of the NCf was characterized by TEM as a spheroid of larger radius 2.5 + 1,1 nm and a smaller radius of 1.9 + 0,6 nm, X-ray diffraction with monoclinic phase and organic load of 35% identified by thermogravimetric analysis. From the viscosimetric measurements, the intrinsic viscosity of the NCf was obtained in the solvents cited using the empirical power equation. With the intrinsic viscosity it was possible to approximate the NCf to a molecule using the Einstein molecular viscosity model and find the hydrodynamic radius (Rh) with values of 4.2 + 0.1 nm for hexane, 4.1 + 0.2 nm for toluene and 4.0 ± 0.2 nm for chloroform. These Rh values were compared to nanostructure characterization techniques, low angle X-ray scattering (SAXS) and dynamic light scattering (DLS). The SAXS values were 4.2 ± 0.1 nm for the NCf in hexane and 4.0 ± 0.1 nm in toluene, not having counts in chloroform due to high X-ray absorption by the solvent. With DLS the values found were 7.0 ± 0.1 nm for the hexane dispersion, 4.9 ± 1.5 nm for the toluene and 3.5 ± 0.3 nm for the chloroform. There was excellent agreement of the data showing the success of the approach of the nanocrystal to a molecule and the viscosimetric characterization. It was observed the importance of the organic layer in the NCf behavior, which represents more than 85% of the volume and is responsible for the high dispersivity of nanocrystals even in high mass fractions (mixture of 80% by mass of NCf in dispersions using toluene). The one-step synthesis in oleic acid showed excellent reproducibility, which allowed the elaboration of this project that used more than 20 g of NCf, an amount considered as ultra-high scale for this type of nanomaterial. The unique properties of this NCf together with the detailed understanding of its behavior in solutions and high-scale synthesis denote a nanomaterial with potential for various industrial applications.

This study synthesized a new chlorhexidine(CHX)-carrier nanosystem based on iron oxide magnetic nanoparticles (IONPs) and chitosan (CS), as well as evaluated its antimicrobial effect on biofilms of Candida albicans and Streptococcus mutans. Method: The IONPs-CS-CHX nanosystem was prepared by CHX interaction to CS-coated IONPs and characterized by X-ray powder diffraction, Fourier transform infrared spectroscopy, transmission electron microscopy and dynamic light scattering. Minimum inhibitory concentration (MIC) of the IONPs-CS-CHX nanosystem was determined according to the broth microdilution assay. After, mono- and dual-species biofilms of C. albicans and S. mutans were formed for 24 hours into wells of 96-well plates in the presence of the nanosystem containing CHX at 39 (IONPs-CS-CHX39) or 78 μg/mL (IONPs-CS-CHX78). Moreover, pre-formed biofilms (24 h) were treated for 24 h with the nanosystem at the same concentrations. The antibiofilm effect was determined by quantification of cultivable cells, total biomass and metabolic activity. Appropriate controls were included in all analyzes. Data were analyzed by Kruskal-Wallis’ test and one-way ANOVA, followed by Student-Newman-Keuls and Holm-Sidak tests (α = 0.05). Results: Characterization results confirmed the nanosystem formation without altering the crystalline properties of the IONPs. In addition, the characteristic absorption bands of each compound were identified in the infrared spectrum, and the mean diameter of the nanosystem was lower than 40 nm. MIC results showed that the nanosystem was slightly more effective than CLX in inhibiting the growth of the microorganisms tested. Biofilms formed in the presence of IONPs-CS-CHX39 attained similar quantitative levels to those observed for CHX at 78 μg/mL. Further, for mono- and dual-species biofilms, IONPs-CS-CHX78 showed similar or superior antibiofilm effects when compared with IONPs-CS-CHX39 and free CHX at 78 μg/mL. Conclusion: The IONPs-CS-CHX nanosystem was able to reduce biofilm formation and pre-formed biofilms of C. albicans and S. mutans in single or mixed cultures. The development of this nanosystem establishes several possibilities for exploration of magnetic nanoparticle-based therapy as drug carrier used in health area.(…)

The use of inorganic nanoparticles in polymer nanocomposites allows gain in mechanical resistance and new properties. However, the incorporation of organic layer functionalized nanoparticles alters the material’s properties in a not fully understood manner. This work has the objective of analyzing the nature of interaction between the organic layer functionalized nanoparticles and the commercial polyurethane adhesive matrix (Adcote 555) and the consequences over physical-chemical properties in relation to the mass percentage of nanoparticles added. The nanoparticles were synthesized with a magnetite core and a poly(1,4-butanediol) organic shell. The mixtures were divided in two groups: low nanoparticles concentration, from 0,05%wt to 5,0%wt, and highly concentrated, up to 90%wt. Tensile and DSC tests allowed the nanocomposites mechanical and thermal properties analysis, respectively. MET imaging and SAXS analysis allowed to determine inorganic core and organic shell sizes, respectively. The nanocomposites’ mechanical behavior wasn’t the expected for conventional nanocomposites. On the contrary, the organic shell seems to have a camouflage effect over the inorganic core and the mechanical and thermal behavior seem the be guided more strongly by the volumetric fraction of the nanoparticles organic shell than their inorganic cores. Thus, it was concluded that the nanocomposites’ properties are ruled by the interphase between matrix and organic shell. The magnetite core’s contribution was to attribute magnetic properties to the highly concentrated nanocomposites.

This study synthesized and characterized a chlorhexidine (CHX)-carrier nanosystem based on iron oxide magnetic nanoparticles (IONPs) and chitosan (CS), and evaluated its antimicrobial effect on mono- and dual-species biofilms of Candida albicans and Streptococcus mutans. CHX was directly solubilized in CS-coated IONPs and maintained under magnetic stirring for obtaining the IONPs-CS-CHX nanosystem. Antimicrobial susceptibility testing for planktonic cells was performed by determining the minimum inhibitory concentration (MIC) of the nanosystem and controls. The effects of the IONPs-CS-CHX nanosystem on the formation of mono- and dual-species biofilms, as well as on pre-formed biofilms were assessed by quantification of total biomass, metabolic activity and colony-forming units. Data were analyzed by the Kruskal-Wallis’ test or one-way analysis of variance, followed by the Student-Newman-Keuls’ or Holm-Sidak’s tests (α = 0.05), respectively. Physico-chemical results confirmed the formation of a nanosystem with a size smaller than 40 nm. The IONPs-CS-CHX nanosystem and free CHX showed similar MIC values for both species analyzed. In general, biofilm quantification assays revealed that the CHX nanosystem at 78 μg/mL promoted similar or superior antibiofilm effects compared to its counterpart at 39 μg/mL and free CHX at 78 μg/mL. These findings highlight the potential of CS-coated IONPs as preventive or therapeutic agents carrying CHX to fight biofilm-associated oral diseases.

The Fe3O4@Poly(1,4-butanediol)/polyurethane nanocomposite is a highly interphase-dependable material with unique characteristics. Firstly, the nanoparticle’s organic shell allows simple fabrication of very well dispersed nanocomposites and the incorporation of extremely high amounts of nanoparticles (NP) into the polymer matrix. Secondly, both chemical and physical aspects of the nanoparticles determine the material’s mechanical behavior. The chemical functionality of the organic layer – free hydroxyl groups at the end of the tethered chains – ensures the material’s stiffening through covalent bonds with the matrix, while being at molten state provides high flexibility and deformability yet maintaining mechanical resistance. As a result, nanocomposites at the low concentration region show increased elastic modulus and tensile strength and slight increase in total strain, while highly concentrated nanocomposites show reduction of elastic modulus and tensile strength and roughly double the total strain. The combination of the chemical and physical functionalities ensures high compatibility between nanoparticles and matrix and allows the production of highly concentrated – above 90% in weight – nanocomposites as a cohesive and flexible material, instead of a brittle wafer. This bifunctionality effect is unprecedented and the results open a wide range of new possibilities in the tailoring of functional nanomaterials for all sorts of applications in materials science.

Overexposure of microorganisms to conventional drugs has led to resistant species that require new treatment strategies. This study prepared and characterized a nanocarrier of miconazole (MCZ) based on iron oxide nanoparticles (IONPs) functionalized with chitosan (CS), and tested its antifungal activity against biofilms of Candida albicans and Candida glabrata. IONPs-CS-MCZ nanocarrier was prepared by loading MCZ on CS-covered IONPs and characterized by physicochemical methods. Minimum inhibitory concentration (MIC) of the nanocarrier was determined by the microdilution method. Biofilms were developed (48 h) in microtiter plates and treated with MCZ-carrying nanocarrier at 31.2 and 78 μg/mL, in both the presence and absence of an external magnetic field (EMF). Biofilms were evaluated by total biomass, metabolic activity, cultivable cells (CFU), extracellular matrix components, scanning electron microscopy and confocal microscopy. Data were analyzed by two-way ANOVA and Holm-Sidak test (p < 0.05). A nanocarrier with diameter lower than 50 nm was obtained, presenting MIC values lower than those found for MCZ, and showing synergism for C. albicans and indifference for C. glabrata (fractional inhibitory concentration indexes of <0.12 and <0.53, respectively). IONPs-CS-MCZ did not affect total biomass and extracellular matrix. IONPs-CS-MCZ containing 78 μg/mL MCZ showed a superior antibiofilm effect to MCZ in reducing CFU and metabolism for single biofilms of C. albicans and dual-species biofilms. The EMF did not improve the nanocarrier effects. Microscopy confirmed the antibiofilm effect of the nanocarrier. In conclusion, IONPs-CS-MCZ was more effective than MCZ mainly against C. albicans planktonic cells and number of CFU and metabolism of the biofilms.