Characterization of organic matter of plants from lakes by thermal analysis in a N2 atmosphere

Thermal Characteristics and Kinetics of the Thermal Degradation of Sugar Beet Waste Leaves and Pulp in Relation to Chemical Composition

Thermal characteristics of dried sugar beet pulp, leaves and leaf fractions obtained after extraction: fibrous leaf pulp and fibre rich leaf fraction, were investigated by differential scanning calorimetry and thermogravimetry. The sugar beet samples showed a similar thermal behaviour associated with a similar composition. Two endotherms are found on the differential scanning calorimetry curves. First one in the temperature range 31-153 °C and the second from 150-160 °C. Thermal degradation kinetics was studied by thermogravimetric analysis. Four degradation stages were observed within the temperature range 25-700 °C. The kinetic parameters of the degradation, obtained by Ortega and Friedman non-isothermal isoconversional methods did not significantly differ between models: Ea-activation energy at a conversion degree 0.1-0.9 ranged 50-200 kJ/mol; lnA- the natural logarithm of the pre-exponential factor 8-48; kp1-thermal degradation rate constant at a conversion extent of 0.5 ranged of 0.19-2.55 min-1. Constant rate of degradation is highest for the sugar beet leaves kp1 (2.58-2.55 min-1), and kp2 (70.1-70.4 min-1). The results obtained are valuable for sugar beet leaf industrial processing. A positive environmental impact is achieved by transforming the waste into high-value food additives.

Integrating an antimicrobial nanocomposite to bioactive electrospun fibers for improved wound dressing materials

This study investigates the fabrication and characterization of electrospun poly (ε-caprolactone)/poly (vinyl pyrrolidone) (PCL/PVP) fibers integrated with a nanocomposite of chitosan, silver nanocrystals, and graphene oxide (ChAgG), aimed at developing advanced wound dressing materials. The ChAgG nanocomposite, recognized for its antimicrobial and biocompatible properties, was incorporated into PCL/PVP fibers through electrospinning techniques. We assessed the resultant fibers' morphological, physicochemical, and mechanical properties, which exhibited significant enhancements in mechanical strength and demonstrated effective antimicrobial activity against common bacterial pathogens. The findings suggest that the PCL/PVP-ChAgG fibers maintain biocompatibility and facilitate controlled therapeutic delivery, positioning them as a promising solution for managing chronic and burn-related wounds. This study underscores the potential of these advanced materials to improve healing outcomes cost-effectively, particularly in settings plagued by high incidences of burn injuries. Further clinical investigations are recommended to explore these innovative fibers' full potential and real-world applicability.

Boosting Drug Discovery for Parkinson's: Enhancement of the Delivery of a Monoamine Oxidase-B Inhibitor by Brain-Targeted PEGylated Polycaprolactone-Based Nanoparticles

The current pharmacological treatments for Parkinson's disease only offer symptomatic relief to the patients and are based on the administration of levodopa and catechol-O-methyltransferase or monoamine oxidase-B inhibitors (IMAO-B). Since the majority of drug candidates fail in pre- and clinical trials, due largely to bioavailability pitfalls, the use of polymeric nanoparticles (NPs) as drug delivery systems has been reported as an interesting tool to increase the stealth capacity of drugs or help drug candidates to surpass biological barriers, among other benefits. Thus, a novel potent, selective, and reversible IMAO-B (chromone C27, IC50 = 670 ± 130 pM) was encapsulated in poly(caprolactone) (PCL) NPs by a nanoprecipitation process. The resulting C27-loaded PEGylated PCL NPs (~213 nm) showed high stability and no cytotoxic effects in neuronal (SH-SY5Y), epithelial (Caco-2), and endothelial (hCMEC/D3) cells. An accumulation of PEGylated PCL NPs in the cytoplasm of SH-SY5Y and hCMEC/D3 cells was also observed, and their permeation across Caco-2 and hCMEC/D3 cell monolayers, used as in vitro models of the human intestine and blood-brain barrier, respectively, was demonstrated. PEGylated PCL NPs delivered C27 at concentrations higher than the MAO-B IC50 value, which provides evidence of their relevance to solving the drug discovery pitfalls.

Correlations between slow pyrolysis characteristics and organic carbon structure of aquatic plant biomass

Thermal analysis techniques have been widely used to characterize natural organic matter; in particular, thermal oxidation has been used to examine soil and sediment organic matter. However, few studies have characterized natural organic matter (NOM) by using slow thermal degradation under a N₂ atmosphere. ¹³C nuclear magnetic resonance (NMR) spectroscopy, UV-Vis spectroscopy, and three-dimensional excitation and emission matrix (EEM) fluorescence spectroscopy were used to characterize aquatic plant biomass for the detailed interpretation of the structures of organic carbon during slow pyrolysis. There was a significant linear correlation between the absorption of heat (99-110 °C) and the loss of mass (110-160 °C) (r² = 0.507, p = 0.01), which indicates that the initial slight loss in mass of the plant materials was due to the loss of less thermally stable components. The release of heat (277-311 °C) and the ratio of the specific absorbances at 253 and 203 nm (A_253/203) were also correlated (r² = 0.388, p = 0.008), which suggests that the release of plant biomass upon heating was associated with the proportion of substituent groups on aromatic rings and that the release of heat increased with the amount of substitution. The coefficient of determination (r²) between fulvic acid-like fluorescence peaks and the loss of mass (230-340 °C) was 0.236 (p = 0.048). This result indicates that the loss of mass in the plant material samples was related to fulvic acid-like substances. More specifically, the reason for this result was the splitting of some aromatic functional groups, such as ether bonds, carbonyl groups, and oxygen heterocycles. In conclusion, these results suggest that the developed correlations between slow pyrolysis characteristics and organic carbon structures contribute to the investigation of the inner chemical structures of natural organic matter.

Detection and Quantification of Graphene-Family Nanomaterials in the Environment

An increase in production of commercial products containing graphene-family nanomaterials (GFNs) has led to concern over their release into the environment. The fate and potential ecotoxicological effects of GFNs in the environment are currently unclear, partially due to the limited analytical methods for GFN measurements. In this review, the unique properties of GFNs that are useful for their detection and quantification are discussed. The capacity of several classes of techniques to identify and/or quantify GFNs in different environmental matrices (water, soil, sediment, and organisms), after environmental transformations, and after release from a polymer matrix of a product is evaluated. Extraction and strategies to combine methods for more accurate discrimination of GFNs from environmental interferences as well as from other carbonaceous nanomaterials are recommended. Overall, a comprehensive review of the techniques available to detect and quantify GFNs are systematically presented to inform the state of the science, guide researchers in their selection of the best technique for the system under investigation, and enable further development of GFN metrology in environmental matrices. Two case studies are described to provide practical examples of choosing which techniques to utilize for detection or quantification of GFNs in specific scenarios. Because the available quantitative techniques are somewhat limited, more research is required to distinguish GFNs from other carbonaceous materials and improve the accuracy and detection limits of GFNs at more environmentally relevant concentrations.

Use of thermal analysis coupled with differential scanning calorimetry, quadrupole mass spectrometry and infrared spectroscopy (TG-DSC-QMS-FTIR) to monitor chemical properties and thermal stability of fulvic and humic acids

Thermogravimetry–coupled with differential scanning calorimetry, quadrupole mass spectrometry, and Fourier-transform infrared spectroscopy (TG-DSC-QMS-FTIR)–was applied to monitor the thermal stability (in an N₂ pyrolytic atmosphere) and chemical properties of natural polymers, fulvic (FA) and humic acids (HA), isolated from chemically different soils. Three temperature ranges, R1, 40–220°C; R2, 220–430°C; and R3, 430–650°C, were distinguished from the DSC data, related to the main thermal processes of different structures (including transformations without weight loss). Weight loss (ΔM) estimated from TG curves at the above temperature intervals revealed distinct differences within the samples in the content of physically adsorbed water (at R1), volatile and labile functional groups (at R2) as well as recalcitrant and refractory structures (at R3). QMS and FTIR modules enabled the chemical identification (by masses and by functional groups, respectively) of gaseous species evolved during thermal decomposition at R1, R2 and R3. Variability in shape, area and temperature of TG, DSC, QMS and FTIR peaks revealed differences in thermal stability and chemical structure of the samples between the FAs and HAs fractions of different origin. The statistical analysis showed that the parameters calculated from QMS (areas of m/z = 16, 17, 18, 44), DSC (Max_DSC) and TG (ΔM) at R1, R2 and R3 correlated with selected chemical properties of the samples, such as N, O and COOH content as well as E2/E6 and E2/E4 indexes. This indicated a high potential for the coupled method to monitor the chemical changes of humic substances. A new humification parameter, H_TD, based on simple calculations of weight loss at specific temperature intervals proved to be a good alternative to indexes obtained from other methods. The above findings showed that the TG-DSC-QMS-FTIR coupled technique can represent a useful tool for the comprehensive assessment of FAs and HAs properties related to their various origin.