Turibius Simon

Novel pyrene containing monomeric and dimeric supramolecular AIEE active nano-probes utilized in selective “off–on” trivalent metal and highly acidic pH sensing with live cell applications

Two novel pyrene containing monomeric and dimeric Schiff base derivatives PCS1 and PCS2 have been synthesized via one-pot reaction and their nano-J-type aggregation induced emission enhancement (AIEE) was well demonstrated using UV-Vis/PL, transmission electron microscopy (TEM), dynamic light scattering (DLS), time resolved photoluminescence (TRPL), and live cell imaging studies. In contrast to PCS2, PCS1 in CH3CN exhibits fluorescence “off–on” sensor selectivity towards transition trivalent metal ions (Fe3+, Cr3+ and Al3+) among other metals, via PET inhibition with excimer PCS1–PCS1* formation. The 2 : 1 stoichiometry of PCS1⋯M3+ (M = Fe/Cr/Al) sensor complexes was calculated from Jobs plots based on their PL titrations. In addition, the binding sites of PCS1⋯M3+ sensor complexes were well recognised from the 1H NMR titrations and supported by ESI(+ve) mass and FTIR analysis. Additionally, fluorescence reversibilities of PCS1⋯M3+ were observed via consequent addition of M3+ ions and PMDTA, respectively. Furthermore, the detection limits (LODs) and the association constant (Ka) values of PCS1⋯M3+ complexes were calculated using standard deviation and linear fittings. Likewise, quantum yield (Φ) measurements, TEM analysis, determination of the effect of pH, density functional theory (DFT) and time resolved photoluminescence (TRPL) studies were performed for the PCS1⋯M3+ sensor complexes. More importantly, confocal fluorescence microscopy imaging of Raw264.7 cells showed that PCS1 could be used as an effective fluorescent probe for detecting transition trivalent metal ions (Fe3+, Cr3+, and Al3+) in living cells. Impressively, both PCS1 and PCS2 showed “off–on” sensing at highly acidic pH values (1–3) with live cell applications.

New Synthesis Route of Hydrogel through A Bioinspired Supramolecular Approach: Gelation, Binding Interaction, and in Vitro Dressing

Peptide-based supramolecular hydrogels have been comprehensively investigated in biomaterial applications because of their unique bioactivity, biofunctionality, and biocompatible features. However, the presence of organic building blocks in peptide-based hydrogels often results in low mechanical stability. To expand their practical use and range of applications, it is necessary to develop the tool kit available to prepare bioinspired, peptide-based supramolecular hydrogels with improved mechanical stability. In this paper, we present an innovative electrostatic and cross-linking approach in which naphthyl-Phe-Phe-Cys (NapFFC) oligopeptides are combined with gold nanoparticles (AuNPs) and calcium ions (Ca(2+)) to produce peptide-based supramolecular hydrogels. We further investigate the interactions among NapFFC, AuNPs and Ca(2+) by microscopy. The morphology of the nanofibrous network constructions and the binding forces exhibited from the hydrogel demonstrated that the combination of two mechanisms successfully enhanced the mechanical stability through the formation of a densely entangled fibrous network of peptide multimers that is attributed to the AuNP linkage and Ca(2+)-induced agglomeration. UV-vis spectrophotometry and fluorescence analysis were also used to demonstrate the enhanced stability of the hydrogel under various conditions such as thermal, solvent erosion, pH value and sonication. All results indicate that the presence of AuNPs and Ca(2+) can strengthen the prepared hydrogel by more than doubling the diameter of NapFFC nanofibers, enabling the formation of stronger frameworks and slowing the release of components. Further experiments confirmed that HeLa cells can grow on the bioinspired NapFFC-AuNP hydrogel and exhibit high cell viability and that these cells were killed on contact with a hydrogel containing a drug. Our peptide-based supramolecular hydrogels prepared from the observed electrostatic and cross-linking mechanisn exhibited a significantly improved mechanical stability, making them well suited to use as a drug carrier in hydrogel dressings and as extracellular materials (ECMs) for tissue engineering.

Novel anthracene- and pyridine-containing Schiff base probe for selective “off–on” fluorescent determination of Cu2+ ions towards live cell application

The novel anthracene- and pyridine-containing Schiff base derivative 2-(2-(anthracen-9-ylmethylene)hydrazinyl)pyridine (AP) has been synthesized via one-pot reaction and its fluorescent “off–on” detection of Cu2+ ions, via PET-based mechanism, is reported. The 1 : 1 stoichiometry of AP⋯Cu2+ sensor complex was calculated from Jobs plot based on PL titrations and supported by ESI (+Ve) mass spectral analysis. In addition, the binding sites of AP⋯Cu2+ sensor conjugate were supported by 1H NMR titration. The detection limit (LOD) and association constant (Ka) of AP⋯Cu2+ complex were obtained by standard deviation and linear fittings. Furthermore, quantum yield (Φf), SEM analysis, pH effect, FTIR interpretation and density functional theory (DFT) studies were conducted for the AP⋯Cu2+ sensing conjugate. More decisively, confocal fluorescence microscopy imaging from Raw264.7 cells indicated that AP could be used as an effective fluorescent probe for the analysis of Cu2+ ions in living cells.

Facile synthesis of a biocompatible silver nanoparticle derived tripeptide supramolecular hydrogel for antibacterial wound dressings

Realizing the widespread demand for biocompatible supramolecular hydrogel based wound dressings, we have developed an N-terminally 2(naphthalen-6-yl)acetic acid (Nap) protected Phe–Phe–Cys peptide (Nap-FFC) using a liquid phase method. This Nap-FFC peptide was used to design a supramolecular hydrogel via a self-assembling process. The Nap-FFC short peptides produced stable and transparent silver nanoparticle-based hydrogels (AgNPs@Nap-FFC) wherein the self-assembled Nap-FFC nanofibers acted as scaffolds for the mineralization of silver nanoparticles (AgNPs) and stabilizers of the synthesized AgNPs. The resultant AgNPs@Nap-FFC nanocomposites were characterized using ultraviolet-visible spectrophotometry (UV-vis spectroscopy), Fourier transform infrared spectroscopy (FT-IR), transmission electron microscopy (TEM) and scanning electron microscopy (SEM) combined with energy-dispersive X-ray spectroscopy (EDX) studies. The AgNPs@Nap-FFC nanocomposites showed excellent monodispersity, long term stability, and functional flexibility in comparison to other AgNP based nanocomposites. Furthermore, AgNPs@Nap-FFC exhibited strong inhibition against both Gram-positive (methicillin-resistant Staphylococcus aureus) and Gram-negative (Acinetobacter baumannii) bacteria and, most importantly, they showed favorable biocompatibility towards human cervical carcinoma cells (HeLa cells). Hence, this study implies that AgNPs@Nap-FFC nanocomposites can easily be prepared in a cost-effective manner and can be used effectively for future antibacterial wound dressings.

An Affordable Wet Chemical Route to Grow Conducting Hybrid Graphite-Diamond Nanowires: Demonstration by A Single Nanowire Device

We report an affordable wet chemical route for the reproducible hybrid graphite-diamond nanowires (G-DNWs) growth from cysteamine functionalized diamond nanoparticles (ND-Cys) via pH induced self-assembly, which has been visualized through SEM and TEM images. Interestingly, the mechanistic aspects behind that self-assembly directed G-DNWs formation was discussed in details. Notably, above self-assembly was validated by AFM and TEM data. Further interrogations by XRD and Raman data were revealed the possible graphite sheath wrapping over DNWs. Moreover, the HR-TEM studies also verified the coexistence of less perfect sp2 graphite layer wrapped over the sp3 diamond carbon and the impurity channels as well. Very importantly, conductivity of hybrid G-DNWs was verified via fabrication of a single G-DNW. Wherein, the better conductivity of G-DNW portion L2 was found as 2.4 ± 1.92 × 10−6 mS/cm and revealed its effective applicability in near future. In addition to note, temperature dependent carrier transport mechanisms and activation energy calculations were reported in details in this work. Ultimately, to demonstrate the importance of our conductivity measurements, the possible mechanism behind the electrical transport and the comparative account on electrical resistivities of carbon based materials were provided.

Development of extremely stable dual functionalized gold nanoparticles for effective colorimetric detection of clenbuterol and ractopamine in human urine samples

New glutamic acid (Glu) and polyethylenimine (PE) functionalized ultra-stable gold nanoparticles (PE-Glu-AuNPs) were developed via a simple NaBH4 reduction method. The low toxicity and biocompatibility of PE-Glu-AuNPs were confirmed via an MTT assay in Raw 264.7 cells. Excitingly, PE-Glu-AuNPs were found to be extremely stable at room temperature up to six months and were utilized in an effective colorimetric naked eye assay of clenbuterol (CLB) and ractopamine (RCT) at pH 5. It was found that the selective assay of CLB and RCT is not affected by any other interferences (such as alanine, phenylalanine, NaCl, CaCl2, threonine, cysteine, glycine, glucose, urea and salbutamol). Furthermore, the detection of these β-agonists can be visually accomplished through change color from wine red to purple blue. Notably, the aggregation induced detection of CLB and RCT was well confirmed through transmission electron microscopy (TEM) and dynamic light scattering (DLS) studies. DLS investigations, clearly showed, that in the presence of CLB and RCT, the initial size of PE-Glu-AuNPs (12.8 ± 8.6 nm) was changed to 84.8 ± 52.3 and 79.5 ± 47.8 nm, respectively, via aggregation. Furthermore, the colorimetric assays of CLB and RCT with PE-Glu-AuNPs were effective starting from CLB and RCT concentrations of 200 nM and 400 nM, respectively, and could be visualized using the naked eyes. Remarkably, UV-vis titrations of PE-Glu-AuNPs with CLB and RCT could be used to well estimate their sub nanomolar detection limits (LODs) via standard deviation and linear fittings. The contribution of surface functional groups that support the analyte recognition was confirmed by fourier-transform infrared spectroscopy (FTIR) analysis. Moreover, the CLB and RCT assays with PE-Glu-AuNPs were supported by examination of human urine samples.