Thermodynamic, IR spectral and X-ray diffraction studies of the “β-cyclodextrin-para-aminobenzoic acid” inclusion complex

Exploiting the synergistic effect of β-cyclodextrin functionalized-multi-walled carbon nanotubes and Zn-MOF for the detection of endocrine-disrupting chemical methylparaben

BACKGROUND

The buildup of methylparaben (MP), a broad-spectrum antimicrobial preservative with endocrine-disrupting properties, in environmental sources, especially aquatic systems, has become a significant concern due to its adverse health effects, including allergic reactions, promoting the risk of developing cancer, and inducing reproductive disorders. Hence, introducing inexpensive and easy-to-use monitoring devices for rapid, selective, and sensitive detection and quantification of MP is highly desirable. In this context, electrochemical platforms have proven to be attractive options due to their remarkable features, such as ease of fabrication and use, short response time, and acceptable sensitivity, accuracy, and selectivity.

RESULTS

In this regard, Zn-BTC metal-organic framework (MOF) and multi-walled carbon nanotubes (MWCNTs) functionalized with β-Cyclodextrin (β-CD) were utilized to modify the matrix of a carbon paste electrode (CPE). The morphological and electrochemical characteristics of β-CD-MWCNTs/Zn-BTC/CPE were evaluated using conventional material characterization techniques and electroanalytical methods. The sensor exhibited two linear current responses in concentration ranges of 0.01 mM-0.3 mM and 0.3 mM-6 mM. The limit of detection (LOD) and limit of quantification (LOQ) were calculated to be 3.8 μM and 11.5 μM, respectively. The device demonstrated excellent selectivity, repeatability, reproducibility, and stability over two weeks. Evaluating its applicability in real samples, including personal care products, tap and river water, and human blood serum, achieved recoveries in the range of 96.25 %-105 %, proving its reliability in environmental and industrial applications.

SIGNIFICANCE

Overall, the proposed modified graphitic platform is not only a cheaper and more easily fabricable and applicable option for MP detection compared to other reported conventional and electrochemical devices but also demonstrates exceptional selectivity and satisfactory sensitivity among various reported electrochemical sensors. In addition, the developed electroanalytical tool can be employed for MP measurement in a broader range of real sample matrixes compared to alternative electrochemical platforms.

Chiral Recognition R- and RS- of New Antifungal: Complexation/Solubilization/Dissolution Thermodynamics and Permeability Assay

Novel potential antifungal of 1,2,4-triazole class have been synthesized as pure enantiomer (R-98) and racemic (RS-186). The effect of 2-hydroxypropyl-β-cyclodextrin (CD) on the solubility and permeability of RS-186 and R-98 in terms of chiral recognition was investigated. Phase solubility studies were carried out at 4 temperatures in 0-0.05 M CD concentration range for pH 2.0 and pH 7.4. AL- and AL--type phase-solubility profiles were obtained for both compounds in pH 2.0 and pH 7.4. The racemic formed more stable complexes with CD as compared to R-isomer. Disclosing of chiral discrimination was facilitated using the approach based on the complex consideration of the derived complexation/solubilization/inherent dissolution thermodynamic functions, including the differential parameters between the racemic compound and R-enantiomer. The differences in the thermodynamic parameters determined by the chirality were discussed in terms of the driving forces of the processes and the main interactions of the compounds with CD in solution. The membrane permeability of both samples in the presence of CD was accessed in order to evaluate the specificity of enantioselective transport through the lipophilic membrane. The solubility/permeability interrelation was disclosed. The investigated compounds were classified as medium permeable in pure buffers and low permeable in the presence of 0.01 M CD. The obtained results can be useful for the design of pharmaceutical products in the form of liquid formulations based on the investigated substances.

Tailored cellulose nanocrystals as a functional ultraviolet absorbing nanofiller of epoxy polymers

Epoxy is an extensively used polymer in several applications such as coatings, adhesives, structural composites etc. However, it is a poor ultraviolet (UV) absorber and suffers from UV-degradation, which usually leads to discoloration and loss of structural integrity. In this study, cellulose nanocrystals (CNCs) conjugated with a UV absorbing molecule were investigated as a functional nanomaterial to enhance the UV absorption of epoxy polymers. The grafting of a UV absorbing molecule, para-aminobenzoic acid (PABA), on the surface of CNCs was confirmed using FTIR, proton NMR, and via elemental analysis. The modified CNCs were then incorporated into an epoxy polymer and their efficacy in mitigating the photo-degradation of epoxy was evaluated. For this, a neat epoxy control, native CNCs and modified CNC based nanocomposite specimens were subjected to controlled UV irradiation and the resulting structure-property changes were assessed. Results of UV absorption and discoloration showed that the neat epoxy was impacted the most as a result of the UV irradiation. While the incorporation of native CNCs displayed some UV absorption and reduction in the UV mediated discoloration of the epoxy polymer, the most pronounced effect was obtained in PABA decorated CNC based epoxy nanocomposites. The use of such tailored CNCs has great potential to mitigate UV induced degradation of a range of polymers that are used especially in outdoor applications where direct exposure to UV is significant.

Tailoring MWCNTs and β-Cyclodextrin for Sensitive Detection of Acetaminophen and Estrogen

Monitoring of trace amount of acetaminophen and estrogen in drinking water is of great importance because of their potential links to gastrointestinal diseases and breast and prostate cancers. The sensitive and accurate detection of acetaminophen and estrogen requires the development of advanced sensing materials that possess appropriate number of analyte-capturing sites and suitable signal conduction path. This can be achieved by implementing appropriate chemical attachment of multiwalled carbon nanotubes (MWCNTs) and β-cyclodextrin (βCD). Here, we report a systematic investigation of four types of modified MWCNT-βCD: (1) physical mixing, (2) "click reaction", (3) thionyl chloride esterification, and (4) Steglich esterification. The Steglich esterification is a one-step approach with shorter reaction time, lower reaction temperature, and eliminates handling of air/moisture-sensitive reagents. MWCNT-βCD prepared by Steglich esterification possessed moderate βCD loading (5-10 wt %), large effective surface area, and fast electron transfer. The host-guest interaction of βCD and redox properties of MWCNT enabled sensitive detection of acetaminophen and 17β-estradiol (E2 is a primary female sex hormone) in the range of 0.005-20 and 0.01-15 μM, with low detection limits of 3.3 and 2.5 nM, respectively. We demonstrated accurate detection results of pharmaceutical compositions in water and urine samples. These results indicate that Steglich esterification method may be applied in fabricating pharmaceutical contaminants sensors for health and environmental applications.

Pentynyl Ether of β-Cyclodextrin Polymer and Silica Micro-Particles: A New Hybrid Material for Adsorption of Phenanthrene from Water

A new hybrid material for the removal of polycyclic aromatic hydrocarbons (PAH) from water was prepared by the polymerization of pentynyl beta-cyclodextrin (PyβCD) and silica micro-particles (SMP). Phenanthrene, being one of the important members of the PAH family and a potential risk for environmental pollution, was selected for this study. Results show that phenanthrene removal efficiency of the SMP was improved significantly after hybridization with PyβCD-polymer. Approximately 50% of the phenanthrene was removed in the first 60 min and more than 95% was removed in less than 7 h when 25 mL of the 2 ppm aqueous phenanthrene solution was incubated with the 100 mg of SMP-PyβCD-polymer material. Infrared spectroscopy and thermal gravimetric analysis show that the enhanced efficiency of the SMP-PyβCD-polymer compared to the unmodified SMP was due to the formation of the inclusion complexation of phenanthrene with the PyβCD. These results indicate that SMP-PyβCD polymers have a potential to be applied as molecular filters in water purification systems and also for waste water treatment.

Citrate modified β-cyclodextrin functionalized magnetite nanoparticles: a biocompatible platform for hydrophobic drug delivery

Water dispersible, β-cyclodextrin functionalized, magnetite nanoparticles are shown to be suitable for the delivery of the hydrophobic drug curcumin, with possible multifunctional applications.