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1. Synthesis and Cytotoxicity Studies of Wood-Based Cationic Cellulose Nanocrystals as Potential Immunomodulators

   https://doi.org/10.3390/nano10081603  

   Imtiaz, Yusha; Tuga, Beza; Smith, Christopher W.; Rabideau, Alexander; Nguyen, Long; Liu, Yali; Hrapovic, Sabahudin; Ckless, Karina; Sunasee, Rajesh (August 2020, Nanomaterials)

   null (Ed.)

   Polysaccharides have been shown to have immunomodulatory properties. Modulation of the immune system plays a crucial role in physiological processes as well as in the treatment and/or prevention of autoimmune and infectious diseases. Cellulose nanocrystals (CNCs) are derived from cellulose, the most abundant polysaccharide on the earth. CNCs are an emerging class of crystalline nanomaterials with exceptional physico-chemical properties for high-end applications and commercialization prospects. The aim of this study was to design, synthesize, and evaluate the cytotoxicity of a series of biocompatible, wood-based, cationic CNCs as potential immunomodulators. The anionic CNCs were rendered cationic by grafting with cationic polymers having pendant +NMe3 and +NH3 moieties. The success of the synthesis of the cationic CNCs was evidenced by Fourier transform infrared spectroscopy, dynamic light scattering, zeta potential, and elemental analysis. No modification in the nanocrystals rod-like shape was observed in transmission electron microscopy and atomic force microscopy analyses. Cytotoxicity studies using three different cell-based assays (MTT, Neutral Red, and LIVE/DEAD®) and three relevant mouse and human immune cells indicated very low cytotoxicity of the cationic CNCs in all tested experimental conditions. Overall, our results showed that cationic CNCs are suitable to be further investigated as immunomodulators and potential vaccine nanoadjuvants. 

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2. Spectroscopic Insights of an Emissive Complex between 4′-N,N-Diethylaminoflavonol in Octa-Acid Deep-Cavity Cavitand and Rhodamine 6G

   https://doi.org/10.3390/molecules28114260  

   Santos, Fabiano da; Ramasamy, Elamparuthi; da Luz, Lilian Camargo; Ramamurthy, Vaidhyanathan; Rodembusch, Fabiano Severo (June 2023, Molecules)

   Excited-state chemistry relies on the communication between molecules, making it a crucial aspect of the field. One important question that arises is whether intermolecular communication and its rate can be modified when a molecule is confined. To explore the interaction in such systems, we investigated the ground and excited states of 4′-N,N-diethylaminoflavonol (DEA3HF) in an octa acid-based (OA) confined medium and in ethanolic solution, both in the presence of Rhodamine 6G (R6G). Despite the observed spectral overlap between the flavonol emission and the R6G absorption, as well as the fluorescence quenching of the flavonol in the presence of R6G, the almost constant fluorescence lifetime at different amounts of R6G discards the presence of FRET in the studied systems. Steady-state and time-resolved fluorescence indicate the formation of an emissive complex between the proton transfer dye encapsulated within water-soluble supramolecular host octa acid (DEA3HF@(OA)2) and R6G. A similar result was observed between DEA3HF:R6G in ethanolic solution. The respective Stern–Volmer plots corroborate with these observations, suggesting a static quenching mechanism for both systems. 

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3. Assembled triphenylamine bis -urea macrocycles: exploring photodriven electron transfer from host to guests

   https://doi.org/10.1039/D1CP03000K  

   Islam, Md Faizul; Sindt, Ammon J.; Hossain, Muhammad Saddam; Ayare, Pooja J.; Smith, Mark D.; Vannucci, Aaron K.; Garashchuk, Sophya; Shimizu, Linda S. (October 2021, Physical Chemistry Chemical Physics)

   Absorption of electronic acceptors in the accessible channels of an assembled triphenylamine (TPA) bis -urea macrocycle 1 enabled the study of electron transfer from the walls of the TPA framework to the encapsulated guests. The TPA host is isoskeletal in all host–guest structures analyzed with guests 2,1,3-benzothiadiazole, 2,5-dichlorobenzoquinone and I 2 loading in single-crystal-to-single-crystal transformations. Analysis of the crystal structures highlights how the spatial proximity and orientation of the TPA host and the entrapped guests influence their resulting photophysical properties and allow direct comparison of the different donor–acceptor complexes. Diffuse reflectance spectroscopy shows that upon complex formation 1·2,5-dichlorobenzoquinone exhibits a charge transfer (CT) transition. Whereas, the 1·2,1,3-benzothiadiazole complex undergoes a photoinduced electron transfer (PET) upon irradiation with 365 nm LEDs. The CT absorptions were also identified with the aid of time dependent density functional theory (TD-DFT) calculations. Cyclic voltammetry experiments show that 2,1,3-benzothiadiazole undergoes reversible reduction within the host–guest complex. Moreover, the optical band gaps of the host 1·2,5-dichlorobenzoquinone (1.66 eV), and host 1·2,1,3-benzothiadiazole (2.15 eV) complexes are significantly smaller as compared to the free host 1 material (3.19 eV). Overall, understanding this supramolecular electron transfer strategy should pave the way towards designing lower band gap inclusion complexes. 

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4. Dual cationic–anionic profiling of metabolites in a single identified cell in a live Xenopus laevis embryo by microprobe CE-ESI-MS

   https://doi.org/10.1039/C8AN01999A  

   Portero, Erika P.; Nemes, Peter (January 2019, The Analyst)

   In situ capillary microsampling with capillary electrophoresis (CE) electrospray ionization (ESI) mass spectrometry (MS) enabled the characterization of cationic metabolites in single cells in complex tissues and organisms. For deeper coverage of the metabolome and metabolic networks, analytical approaches are needed that provide complementary detection for anionic metabolites, ideally using the same instrumentation. Described here is one such approach that enables sequential cationic and anionic (dual) analysis of metabolites in the same identified cell in a live vertebrate embryo. A calibrated volume was microaspirated from the animal-ventral cell in a live 8-cell embryo of Xenopus laevis , and cationic and anionic metabolites were one-pot microextracted from the aspirate, followed by CE-ESI-MS analysis of the same extract. A laboratory-built CE-ESI interface was reconfigured to enable dual cationic–anionic analysis with ∼5–10 nM (50–100 amol) lower limit of detection and a capability for quantification. To provide robust separation and efficient ion generation, the CE-ESI interface was enclosed in a nitrogen gas filled chamber, and the operational parameters were optimized for the cone-jet spraying regime in both the positive and negative ion mode. A total of ∼250 cationic and ∼200 anionic molecular features were detected from the cell between m / z 50–550, including 60 and 24 identified metabolites, respectively. With only 11 metabolites identified mutually, the duplexed approach yielded complementary information on metabolites produced in the cell, which in turn deepened network coverage for several metabolic pathways. With scalability to smaller cells and adaptability to other types of tissues and organisms, dual cationic–anionic detection with in situ microprobe CE-ESI-MS opens a door to better understand cell metabolism. 

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5. The function of peptide-mimetic anionic groups and salt bridges in the antimicrobial activity and conformation of cationic amphiphilic copolymers

   https://doi.org/10.1039/D1RA02730A  

   Bhat, Rajani; Foster, Leanna L.; Rani, Garima; Vemparala, Satyavani; Kuroda, Kenichi (June 2021, RSC Advances)

   Herein we report the synthesis of ternary statistical methacrylate copolymers comprising cationic ammonium (amino-ethyl methacrylate: AEMA), carboxylic acid (propanoic acid methacrylate: PAMA) and hydrophobic (ethyl methacrylate: EMA) side chain monomers, to study the functional role of anionic groups on their antimicrobial and hemolytic activities as well as the conformation of polymer chains. The hydrophobic monomer EMA was maintained at 40 mol% in all the polymers, with different percentages of cationic ammonium (AEMA) and anionic carboxylate (PAMA) side chains, resulting in different total net charge for the polymers. The antimicrobial and hemolytic activities of the copolymer were determined by the net charge of +3 or larger, suggesting that there was no distinct effect of the anionic carboxylate groups on the antimicrobial and hemolytic activities of the copolymers. However, the pH titration and atomic molecular dynamics simulations suggest that anionic groups may play a strong role in controlling the polymer conformation. This was achieved via formation of salt bridges between cationic and anionic groups, transiently crosslinking the polymer chain allowing dynamic switching between compact and extended conformations. These results suggest that inclusion of functional groups in general, other than the canonical hydrophobic and cationic groups in antimicrobial agents, may have broader implications in acquiring functional structures required for adequate antimicrobial activity. In order to explain the implications, we propose a molecular model in which formation of intra-chain, transient salt bridges, due to the presence of both anionic and cationic groups along the polymer, may function as “adhesives” which facilitate compact packing of the polymer chain to enable functional group interaction but without rigidly locking down the overall polymer structure, which may adversely affect their functional roles. 

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