The effect of the solvent on the morphology and the particle size of the polymer materials obtained by precipitation polymerization is not yet understood from a physical chemical perspective. ...Clarifying the effect of the solvent is an important issue to understand the thermodynamic principles of precipitation polymerization and forward the engineering aspects. In this work, we use the scaling theory to deduce the thermodynamic equations that control the phase separation process and particle size in precipitation polymerization at constant T and P. To do so, precipitation polymerization has been undertaken in three steps: (I) coil-to-globule transition, (II) phase separation, and (III) growth stage. The model is then used to analyze the effect of the solvent in precipitation polymerization at constant T and P. To prove the model, we focus on analyzing correlations between the theoretical curves and the experimental curves obtained from precipitation polymerization of a model polymeric system in different solvents and show that we can faithfully reproduce the experimental curves by using the theoretical equations. Finally, we exploit the thermodynamic principles of heterogeneous nucleation on fractal surfaces to develop a novel methodology based on precipitation polymerization in the presence of small concentrations of fractal nanostructures and show how this new approach is able to reduce the particle size up to eight times below the values obtained from conventional precipitation polymerization.
to design calcium and zinc-loaded bioactive and cytocompatible nanoparticles for the treatment of periodontal disease.
PolymP-nActive nanoparticles were zinc or calcium loaded. Biomimetic calcium ...phosphate precipitation on polymeric particles was assessed after 7 days immersion in simulated body fluid, by scanning electron microscopy attached to an energy dispersive analysis system. Amorphous mineral deposition was probed by X-ray diffraction. Cell viability analysis was performed using oral mucosa fibroblasts by: 1) quantifying the liberated deoxyribonucleic acid from dead cells, 2) detecting the amount of lactate dehydrogenase enzyme released by cells with damaged membranes, and 3) by examining the cytoplasmic esterase function and cell membranes integrity with a fluorescence-based method using the Live/Dead commercial kit. Data were analyzed by Kruskal-Wallis and Mann-Whitney tests.
Precipitation of calcium and phosphate on the nanoparticles surfaces was observed in calcium-loaded nanoparticles. Non-loaded nanoparticles were found to be non-toxic in all the assays, calcium and zinc-loaded particles presented a dose dependent but very low cytotoxic effect.
The ability of calcium-loaded nanoparticles to promote precipitation of calcium phosphate deposits, together with their observed non-toxicity may offer new strategies for periodontal disease treatment.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Correction for 'An optical sensor for the sensitive determination of formaldehyde gas based on chromotropic acid and 4-aminoazobenzene immobilized in a hydrophilic membrane' by M. D. Fernández-Ramos
...et al.
,
Analyst
, 2023,
148
, 4533-4538,
https://doi.org/10.1039/D3AN01056B
.
This work highlights the relevance of the interactions between polymer and solvent during precipitation polymerization in order to control the morphology and the size of the precipitated material ...without any changes in chemical composition. Thus, a thermodynamic model based on Flory Hugings model and Hansen’s solubility parameters has been proposed in order to control the precipitation process. This model is based on the study and characterization of the interactions (hydrogen-bonding forces, polar forces and dispersion forces) between growing polymeric chains and solvent molecules. The model was corroborated by more than 80 different solvent compositions were used for a ternary solvent mixture (toluene, acetonitrile and 2-propanol) and two different monomer molar ratio feeds (45% MAA, 20% HEMA, and 35% EDMA; 20% MAA, 45% HEMA, and 35% EDMA). The morphologies of the resulting polymer material were characterized by scanning electron microscopy and transmission electron microscopy and the particles sizes were deduced by dynamic light scattering. The polymeric particles with different sizes prepared in this work were used to introduce on them magnetic properties. The results in this work enable the control of the size, chemical composition, and the homogeneous encapsulation of Fe3O4 within different hydrophilic polymeric matrixes by polymerization precipitation, allowing the design of magnetic particles free of any stabilizers.
Polymeric membranes are employed in guided bone regeneration (GBR) as physical barriers to facilitate bone in-growth. A bioactive and biomimetic membrane with the ability to participate in the ...healing and regeneration of the bone is necessary. The aim of the present study was to analyze how novel silicon dioxide composite membranes functionalized with zinc or doxycycline can modulate the osteoblasts' proliferation, differentiation, and expression of selected antigenic markers related to immunomodulation. Nanostructured acrylate-based membranes were developed, blended with silica, and functionalized with zinc or doxycycline. They were subjected to MG63 osteoblast-like cells culturing. Proliferation was assessed by MTT-assay, differentiation by evaluating the alkaline phosphatase activity by a spectrophotometric method and antigenic phenotype was assessed by flow cytometry for selected markers. Mean comparisons were conducted by one-way ANOVA and Tukey tests (
< 0.05). The blending of silica nanoparticles in the tested non-resorbable polymeric scaffold improved the proliferation and differentiation of osteoblasts, but doxycycline doped scaffolds attained the best results. Osteoblasts cultured on doxycycline functionalized membranes presented higher expression of CD54, CD80, CD86, and HLA-DR, indicating a beneficial immunomodulation activity. Doxycycline doped membranes may be a potential candidate for use in GBR procedures in several challenging pathologies, including periodontal disease.
Formaldehyde is a common contaminant in occupational and environmental atmospheres, prolonged exposure leads to health risks, and its determination is necessary to protect health. There is a great ...demand for portable, rapid, and sensitive methods that can be used in resource-limited settings. In this respect, a colorimetric sensor has been developed based on the colour change from pink to purple of co-immobilized chromotropic acid and 4-aminoazobenzene in hydroxypropyl methylcellulose when it is exposed to different concentrations of formaldehyde. The concentration of formaldehyde in the gas phase was quantified by measuring the change of the appropriate colour coordinates in response to the concentration of formaldehyde. A calibration curve was obtained for formaldehyde, with a useful concentration range from 0.08 to 0.6 ppmv. The detection limit was 0.016 ppmv, which is lower than the maximum exposure concentrations recommended by both the World Health Organization (WHO) and the Occupational Safety and Health Administration (OSHA). The optical sensor was found to have good reproducibility, with a relative standard deviation of 2.3 and 1.7% at 0.08 and 0.25 ppmv, respectively. The sensor can operate at room temperature and environmental humidity, 25 °C, and 50% RH, respectively. In addition, a study of interferents (acetaldehyde, toluene, methanol, ethyl acetate, acetone, acetic acid, carbon dioxide and ammonia) showed high selectivity for formaldehyde, which indicates that this membrane is a simple, fast, and economical alternative for quantifying the concentration of formaldehyde in different environments.
Optical sensor for highly selective determination of Formaldehyde gas at room temperature. Irreversible sensor with a detection limit lower than the maximum exposure concentrations recommended by both the WHO and OSHA. Good reproducibility and with only a 5-min response time.
To analyze how novel developed silicon dioxide composite membranes, functionalized with zinc or doxycycline, can modulate the expression of genes related to the osteogenic functional capacity of ...osteoblastic cells.
The composite nanofibers membranes were manufactured by using a novel polymeric blend and 20 nm silicon dioxide nanoparticles (SiO2-NPs). To manufacture the membranes, 20 nm SiO2-NPs were added to the polymer solution and the resulting suspension was processed by electrospinning. In a second step, the membranes were functionalized with zinc or doxycycline. Then, they were subjected to MG63 osteoblast-like cells culturing for 48 h. After this time, real-time quantitative polymerase chain reaction (RT-qPCR) was carried out to study the expression of Runx-2, OSX, ALP, OSC, OPG, RANKL, Col-I, BMP-2, BMP-7, TGF-β1, VEGF, TGF-βR1, TGF- βR2, and TGF-βR3. Mean comparisons were conducted by One-way ANOVA and Tukey tests (p < 0.05).
In general, the blending of SiO2-NPs in the tested non-resorbable polymeric scaffold improves the expression of osteogenic genes over the control membranes. Doxycycline doping of experimental scaffolds attained the best results, encountering up-regulation of BMP-2, ALP, OPG, TGFβ-1 and TGFβ-R1. Membranes with zinc induced a significant increase in the expression of Col-I, ALP and TGF β1. Both, zinc and doxycycline functionalized membranes enormously down-regulated the expression of RANKL.
Zinc and doxycycline doped membranes are bioactive inducing overexpression of several osteogenic gene markers.
Doxycycline doped membranes may be a potential candidate for use in GBR procedures in several challenging pathologies, including periodontal diseases.
Introduction
Demineralized collagen fibers at the hybrid layer are susceptible to degradation. Remineralization may aid to improve bond longevity.
Objectives
The aim of the present study was to ...infiltrate zinc and calcium-loaded polymeric nanoparticles into demineralized dentin to facilitate hybrid layer remineralization.
Materials and methods
Zinc or calcium-loaded polymeric nanoparticles were infiltrated into etched dentin, and Single Bond Adhesive was applied. Bond strength was tested after 24 h and 6 months storage. Nanomechanical properties, dye-assisted confocal laser microscopy, and Masson’s trichrome staining evaluation were performed to assess for the hybrid layer morphology, permeability, and remineralization ability after 24 h and 3 months. Data were analyzed by ANOVA and Student–Newman–Keuls multiple comparisons tests (
p
< 0.05).
Results
Immediate bond strength was not affected by nanoparticles infiltration (25 to 30 MPa), while after 6 months, bond strengths were maintained (22 to 24 MPa). After 3 months, permeability occurred only in specimens in which nanoparticles were not infiltrated. Dentin remineralization, at the bottom of the hybrid layer, was observed in all groups. After microscopy analysis, zinc-loaded nanoparticles were shown to facilitate calcium deposition throughout the entire hybrid layer. Young’s modulus at the hybrid layer increased from 2.09 to 3.25 GPa after 3 months, in specimens with zinc nanoparticles; meanwhile, these values were reduced from 1.66 to 0.49 GPa, in the control group.
Conclusion
Infiltration of polymeric nanoparticles into demineralized dentin increased long-term bond strengths. Zinc-loaded nanoparticles facilitate dentin remineralization within the complete resin–dentin interface.
Clinical relevance
Resin–dentin bond longevity and dentin remineralization at the hybrid layer were facilitated by zinc-loaded nanoparticles.
In this paper, the combination of Solid Surface-Room Temperature Phosphorescence (SS-RTP) and nanotechnology has led to a new approach in the detection of biogenic amines in complex matrices. This ...novel approach allows, for the first time, the direct determination of the concentration of tryptamine in beers. The novelty of the proposed optical sensor resides in its simplicity, rapidity, absence of complex chromatographic separation, sample clean-up, preconcentration, and derivatization protocols. Therefore, this novel methodology simplifies and reduces considerably the time and cost of the analysis, resolving the two major problems of the determination of tryptamine in beer up to now: low sensitivity and matrix effects.
The proposed sensor is based on a novel white, uncharged, and non-luminescent functional nonwoven nanofibre mat (Tiss®-Link) formed by hydrophilic nanofibres of 300nm of diameter functionalized with a high concentration of active vinyl groups (330µmolg−1). It is used to carry out a kinetically controlled covalent immobilisation of tryptamine via Michael type-reaction. The transduction of the sensor is phosphorescence; the covalently immobilized tryptamine is quantified by SS-RTP, obtaining a detection limit of 6ngmL−1 with short response times (15min). The applicability of the sensor was demonstrated by analysing tryptamine in 10 different varieties of beers, obtaining recovery percentages close to 100%.
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