Fluoroquinolone-Based Organic Salts (GUMBOS) with Antibacterial Potential.

Antimicrobial resistance is a silent pandemic considered a public health concern worldwide. Strategic therapies are needed to replace antibacterials that are now ineffective. One approach entails the use of well-known antibacterials along with adjuvants that possess non-antibiotic properties but can extend the lifespan and enhance the effectiveness of the treatment, while also improving the suppression of resistance. In this regard, a group of uniform materials based on organic salts (GUMBOS) presents an alternative to this problem allowing the combination of antibacterials with adjuvants. Fluoroquinolones are a family of antibacterials used to treat respiratory and urinary tract infections with broad-spectrum activity. Ciprofloxacin and moxifloxacin-based GUMBOS were synthesized via anion exchange reactions with lithium and sodium salts. Structural characterization, thermal stability and octanol/water partition ratios were evaluated. The antibacterial profiles of most GUMBOS were comparable to their cationic counterparts when tested against Gram-positive S. aureus and Gram-negative E. coli, except for deoxycholate anion, which demonstrated the least effective antibacterial activity. Additionally, some GUMBOS were less cytotoxic to L929 fibroblast cells and non-hemolytic to red blood cells. Therefore, these agents exhibit promise as an alternative approach to combining drugs for treating infections caused by resistant bacteria.

Perspectives of Three African American Chemists: Reflections on Careers, Experiences, and the Future.

Three African American analytical chemists, whose primary research careers have focused in the respective sectors of academia, government, and industry, have come together to provide personal perspectives on parameters that have impacted their careers as well as to provide their perceptions of the current and future status of African Americans in the overall science, technology, engineering, and mathematics (STEM) enterprise, and the more specific field of analytical chemistry. The authors, having ∼150 years of combined experiences, reflect on the past status and contemplate future advances for African Americans in STEM. The most important factors during their formative years that underpinned their success over the long-term are enumerated. Particularly cited are the distinct features within the Historically Black Colleges and Universities (HBCU) environment that placed them solidly on a path toward successful careers. The Grand Challenge now and for the foreseeable future, reversal of the dysfunctional metropolitan public-school systems, is cited and the only perceived light in the tunnel for addressing this issue is mentioned. Finally, recommendations are made for the future where diversity within the STEM enterprise will be a prerequisite for U.S. competitiveness in our global society.

Pyrene-Benzimidazole Derivatives as Novel Blue Emitters for OLEDs.

Three novel small organic heterocyclic compounds: 2-(1,2-diphenyl)-1H-benzimidazole-7-tert-butylpyrene (compound A), 1,3-di(1,2-diphenyl)-1H-benzimidazole-7-tert-butylpyrene (compound B), and 1,3,6,8-tetra(1,2-diphenyl)-1H-benzimidazolepyrene (compound C) were synthesized and characterized for possible applications as blue OLED emitters. The specific molecular design targeted decreasing intermolecular aggregation and disrupting crystallinity in the solid-state, in order to reduce dye aggregation, and thus obtain efficient pure blue photo- and electroluminescence. Accordingly, the new compounds displayed reasonably high spectral purity in both solution- and solid-states with average CIE coordinates of (0.160 ± 0.005, 0.029 ± 0.009) in solution and (0.152 ± 0.007, 0.126 ± 0.005) in solid-state. These compounds showed a systematic decrease in degree of crystallinity and intermolecular aggregation due to increasing steric hindrance, as revealed using powder X-ray diffraction analysis and spectroscopic studies. An organic light-emitting diode (OLED) prototype fabricated using compound B as the non-doped emissive layer displayed an external quantum efficiency (EQE) of 0.35 (±0.04)% and luminance 100 (±6) cd m-2 at 5.5 V with an essentially pure blue electroluminescence corresponding to CIE coordinates of (0.1482, 0.1300). The highest EQE observed from this OLED prototype was 4.3 (±0.3)% at 3.5 V, and the highest luminance of 290 (±10) cd m-2 at 7.5 V. These values were found comparable to characteristics of the best pure blue OLED devices based on simple fluorescent small-molecule organic chromophores.

Octenidine/carbenicillin GUMBOS as potential treatment for oropharyngeal gonorrhoea.

BACKGROUND: Reducing Neisseria gonorrhoeae colonies in the oropharynx is a viable solution to minimize the transmission of this bacterium amongst individuals. OBJECTIVES: A strategy involving the electrostatic interaction between a common antiseptic and a discontinued antibiotic (i.e. octenidine and carbenicillin) was evaluated as a potential treatment for gonorrhoea. Octenidine/carbenicillin is a novel group of uniform materials based on organic salts (GUMBOS) with inherent in vitro antibacterial activity that comes from its parent antiseptic and antibacterial ions, octenidine and carbenicillin, respectively. METHODS: Antibacterial activities for octenidine dihydrochloride, disodium carbenicillin, octenidine/carbenicillin and stoichiometrically equivalent 1:1 octenidine dihydrochloride to disodium carbenicillin were assessed using the Kirby-Bauer disc diffusion assay for N. gonorrhoeae (ATCC 49226) and three clinical isolates. Predictive permeability using the Parallel Artificial Membrane Permeability Assay and cytotoxicity against HeLa cells was also evaluated. RESULTS: Additive in vitro antibacterial activities against N. gonorrhoeae were observed in this study, which suggests octenidine/carbenicillin could be a useful agent in reducing N. gonorrhoeae transmission and minimizing gonorrhoea infections. Octenidine/carbenicillin also exhibited bioequivalence to azithromycin and doxycycline, two currently prescribed antibiotics. Likewise, octenidine/carbenicillin had improved predicted permeability compared with octenidine dihydrochloride. CONCLUSIONS: Antimicrobial GUMBOS synthesized in this study could be used as an adjunctive treatment approach to current drug therapies for oropharyngeal gonorrhoea infection control and prevention.

Quartz Crystal Microbalance Based Sensor Arrays for Detection and Discrimination of VOCs Using Phosphonium Ionic Liquid Composites.

Herein, we examine two sensing schemes for detection and discrimination of chlorinated volatile organic compounds (VOCs). In this work, phosphonium ionic liquids (ILs) were synthesized and vapor sensing properties examined and compared to phosphonium IL-polymer composites. Pure IL sensors were used to develop a QCM-based multisensory array (MSA), while IL-polymer composites were used to develop an MSA and virtual sensor arrays (VSAs). It was found that by employing the composite MSA, five chlorinated VOCs were accurately discriminated at 95.56%, which was an increase in accuracy as compared to pure ILs MSA (84.45%). Data acquired with two out of three VSAs allowed discrimination of chlorinated VOCs with 100% accuracy. These studies have provided greater insight into the benefits of incorporating polymers in coating materials for enhanced discrimination accuracies of QCM-based sensor arrays. To the best of our knowledge, this is the first report of a QCM-based VSA for discrimination of closely related chlorinated VOCs.

QCM Sensor Arrays, Electroanalytical Techniques and NIR Spectroscopy Coupled to Multivariate Analysis for Quality Assessment of Food Products, Raw Materials, Ingredients and Foodborne Pathogen Detection: Challenges and Breakthroughs.

Quality checks, assessments, and the assurance of food products, raw materials, and food ingredients is critically important to ensure the safeguard of foods of high quality for safety and public health. Nevertheless, quality checks, assessments, and the assurance of food products along distribution and supply chains is impacted by various challenges. For instance, the development of portable, sensitive, low-cost, and robust instrumentation that is capable of real-time, accurate, and sensitive analysis, quality checks, assessments, and the assurance of food products in the field and/or in the production line in a food manufacturing industry is a major technological and analytical challenge. Other significant challenges include analytical method development, method validation strategies, and the non-availability of reference materials and/or standards for emerging food contaminants. The simplicity, portability, non-invasive, non-destructive properties, and low-cost of NIR spectrometers, make them appealing and desirable instruments of choice for rapid quality checks, assessments and assurances of food products, raw materials, and ingredients. This review article surveys literature and examines current challenges and breakthroughs in quality checks and the assessment of a variety of food products, raw materials, and ingredients. Specifically, recent technological innovations and notable advances in quartz crystal microbalances (QCM), electroanalytical techniques, and near infrared (NIR) spectroscopic instrument development in the quality assessment of selected food products, and the analysis of food raw materials and ingredients for foodborne pathogen detection between January 2019 and July 2020 are highlighted. In addition, chemometric approaches and multivariate analyses of spectral data for NIR instrumental calibration and sample analyses for quality assessments and assurances of selected food products and electrochemical methods for foodborne pathogen detection are discussed. Moreover, this review provides insight into the future trajectory of innovative technological developments in QCM, electroanalytical techniques, NIR spectroscopy, and multivariate analyses relating to general applications for the quality assessment of food products.

Efficient Low-Cost Procedure for Microextraction of Estrogen from Environmental Water Using Magnetic Ionic Liquids.

In this study, three magnetic ionic liquids (MILs) were investigated for extraction of four estrogens, i.e., estrone (E1), estradiol (E2), estriol (E3), and ethinylestradiol (EE2), from environmental water. The cation trihexyl(tetradecyl)phosphonium ([P66614]+), selected to confer hydrophobicity to the resulting MIL, was combined with tetrachloroferrate(III), ferricyanide, and dysprosium thiocyanate to yield ([P66614][FeCl4]), ([P66614]3[Fe(CN)6]), and ([P66614]5[Dy(SCN)8]), respectively. After evaluation of various strategies to develop a liquid-liquid microextraction technique based on synthesized MILs, we placed the MILs onto a magnetic stir bar and used them as extracting solvents. After extraction, the MIL-enriched phase was dissolved in methanol and injected into an HPLC-UV for qualitative and quantitative analysis. An experimental design was used to simultaneously evaluate the effect of select variables and optimization of extraction conditions to maximize the recovery of the analytes. Under optimum conditions, limits of detection were in the range of 0.2 (for E3 and E2) and 0.5 µg L-1 (for E1), and calibration curves exhibited linearity in the range of 1-1000 µg L-1 with correlation coefficients higher than 0.998. The percent relative standard deviation (RSD) was below 5.0%. Finally, this method was used to determine concentration of estrogens in real lake and sewage water samples.

Influence of Anion Variations on Morphological, Spectral, and Physical Properties of the Propidium Luminophore.

Propidium iodide (3,8-diamino-5-[3-(diethylmethylammonio)propyl]-6-phenylphenanthridinium diiodide, [P][I]), is a well-known red fluorescent dye that is widely used for biological applications such as staining. In this study, we have replaced the iodide counteranion of [P][I] with three hydrophobic and bulky organic anions, trifluoromethanesulfonate/[TfO], bis(trifluoromethanesulfonyl)imide/[NTf2], and bis(perfluoroethylsulfonyl)imide/[BETI], and have thus obtained a propidium-derived group of uniform materials based on organic salts (PGUMBOS). The morphological, spectral, and physical properties of these materials were investigated in order to understand the impact of anion variations. While [P][I] is a crystalline solid, propidium salts with [BETI] or [NTf2] counteranions, i.e., [P][BETI] and [P][NTf2], have significantly lower crystallinity as reflected in powder X-ray diffraction data. In addition, [P][BETI] and [P][NTf2] exhibited improved photothermal stability as compared to [P][I] when examined using thermogravimetric analysis and time-dependent kinetic fluorescence experiments under the given experimental conditions. Spectral and electronic properties of the propidium luminophore were not significantly changed upon anion variations, although fluorescence lifetimes and quantum yields showed a systematic increase with decreasing solvent polarity. The experimental HOMO-LUMO energy gaps of these compounds were ∼2 eV with energies of HOMO and LUMO orbitals obtained as -5.15 (±0.08) and -3.19 (±0.08) eV.

Endocytic Selective Toxicity of Rhodamine 6G nanoGUMBOS in Breast Cancer Cells.

Herein, we report on the role of endocytosis in the selective chemotherpeutic toxicity of rhodamine 6G (R6G) based nanomaterials, i.e., nanoGUMBOS, that are derived from a group of uniform materials based on organic salts (GUMBOS). Evaluation of cellular uptake in the presence and absence of endocytosis inhibitors suggests nanoGUMBOS internalization via clathrin-mediated endocytosis in cancer cells and reveals lack of endocytic internalization in normal cells. Results from characterization of these nanomaterials suggest that endocytic internalization in cancer cells leads to nanoGUMBOS dissociation within the endosomal environment. This ultimately results in selective cytotoxicity of the nanoGUMBOS for cancer cells with no toxicity toward normal cells under examined conditions. Following examination of the selectivity mechanism, in vivo investigations were performed to examine potential therapeutic properties of these nanoparticles. Remarkably, nanoGUMBOS treatment using a mouse xenograft model reduced the tumor volume by 50% suggesting retention of in vitro therapeutic properties in vivo. These results corroborate the selective behavior of nanoGUMBOS and demonstrate their in vivo therapeutic effects, providing further insight into the possible use of these nanomaterials as potential chemotherapeutic agents.

Ultrafast and nonlinear spectroscopy of brilliant green-based nanoGUMBOS with enhanced near-infrared emission.

The synthesis, characterization, ultrafast dynamics, and nonlinear spectroscopy of 30 nm nanospheres of brilliant green-bis(pentafluoroethylsulfonyl)imide ([BG][BETI]) in water are reported. These thermally stable nanoparticles are derived from a group of uniform materials based on organic salts (nanoGUMBOS) that exhibit enhanced near-infrared emission compared with the molecular dye in water. The examination of ultrafast transient absorption spectroscopy results reveals that the overall excited-state relaxation lifetimes of [BG][BETI] nanoGUMBOS are longer than the brilliant green molecular dye in water due to steric hindrance of the torsional degrees of freedom of the phenyl rings around the central carbon. Furthermore, the second harmonic generation signal of [BG][BETI] nanoGUMBOS is enhanced by approximately 7 times and 23 times as compared with colloidal gold nanoparticles of the same size and the brilliant green molecular dye in water, respectively. A very clear third harmonic generation signal is observed from the [BG][BETI] nanoGUMBOS but not from either the molecular dye or the gold nanoparticles. Overall, these results show that [BG][BETI] nanoGUMBOS exhibit altered ultrafast and nonlinear spectroscopy that is beneficial for various applications including nonlinear imaging probes, biomedical imaging, and molecular sensing.

Rational Design of QCM-D Virtual Sensor Arrays Based on Film Thickness, Viscoelasticity, and Harmonics for Vapor Discrimination.

Herein, we demonstrate an alternative strategy for creating QCM-based sensor arrays by use of a single sensor to provide multiple responses per analyte. The sensor, which simulates a virtual sensor array (VSA), was developed by depositing a thin film of ionic liquid, either 1-octyl-3-methylimidazolium bromide ([OMIm][Br]) or 1-octyl-3-methylimidazolium thiocyanate ([OMIm][SCN]), onto the surface of a QCM-D transducer. The sensor was exposed to 18 different organic vapors (alcohols, hydrocarbons, chlorohydrocarbons, nitriles) belonging to the same or different homologous series. The resulting frequency shifts (Δf) were measured at multiple harmonics and evaluated using principal component analysis (PCA) and discriminant analysis (DA) which revealed that analytes can be classified with extremely high accuracy. In almost all cases, the accuracy for identification of a member of the same class, that is, intraclass discrimination, was 100% as determined by use of quadratic discriminant analysis (QDA). Impressively, some VSAs allowed classification of all 18 analytes tested with nearly 100% accuracy. Such results underscore the importance of utilizing lesser exploited properties that influence signal transduction. Overall, these results demonstrate excellent potential of the virtual sensor array strategy for detection and discrimination of vapor phase analytes utilizing the QCM. To the best of our knowledge, this is the first report on QCM VSAs, as well as an experimental sensor array, that is based primarily on viscoelasticity, film thickness, and harmonics.

Virtual colorimetric sensor array: single ionic liquid for solvent discrimination.

There is a continuing need to develop high-performance sensors for monitoring organic solvents, primarily due to the environmental impact of such compounds. In this regard, colorimetric sensors have been a subject of intense research for such applications. Herein, we report a unique virtual colorimetric sensor array based on a single ionic liquid (IL) for accurate detection and identification of similar organic solvents and mixtures of such solvents. In this study, we employ eight alcohols and seven binary mixtures of ethanol and methanol as analytes to provide a stringent test for assessing the capabilities of this array. The UV-visible spectra of alcoholic solutions of the IL used in this study show two absorption bands. Interestingly, the ratio of absorbance for these two bands is found to be extremely sensitive to alcohol polarity. A virtual sensor array is created by using four different concentrations of IL sensor, which allowed identification of these analytes with 96.4-100% accuracy. Overall, this virtual sensor array is found to be very promising for discrimination of closely related organic solvents.

Strategy for tuning the photophysical properties of photosensitizers for use in photodynamic therapy.

A novel approach for tuning spectral properties, as well as minimizing aggregation, in zinc porphyrin and zinc phthalocyanine-based compounds is presented. Particular emphasis is placed on use of these compounds as photosensitizers in photodynamic therapy (PDT). To accomplish this aim, a bulky hydrophobic cation, trihexyltetradecylphosphonium, is paired with anionic porphyrin and phthalocyanine dyes to produce a group of uniform materials based on organic salts (GUMBOS) that absorb at longer wavelengths with high molar absorptivity and high photostability. Nanoparticles derived from these GUMBOS possess positively charged surfaces with high zeta potential values, which are highly desirable for PDT. Upon irradiation at longer wavelengths, these GUMBOS produced singlet oxygen with greater efficiency as compared to the respective parent dyes.

Spectral and physicochemical characterization of dysprosium-based multifunctional ionic liquid crystals.

We report on the synthesis and characterization of multifunctional ionic liquid crystals (melting points below 100 °C) which possess chirality and fluorescent behavior as well as mesomorphic and magnetic properties. In this regard, (1R,2S)-(-)-N-methylephedrine ((-)MeEph), containing a chiral center, is linked with variable alkyl chain lengths (e.g., 14, 16, and 18 carbons) to yield liquid crystalline properties in the cations of these compounds. A complex counteranion consisting of trivalent dysprosium (Dy(3+)) and thiocyanate ligand (SCN(-)) is employed, where Dy(3+) provides fluorescent and magnetic properties. Examination of differential scanning calorimetry (DSC) and hot-stage polarizing optical microscopy (POM) data confirmed liquid crystalline characteristics in these materials. We further report on phase transitions from solid to liquid crystal states, followed by isotropic liquid states with increasing temperature. These compounds exhibited two characteristic emission peaks in acetonitrile solution and the solid state when excited at λex = 366 nm, which are attributed to transitions from (4)F9/2 to (6)H15/2 and (4)F9/2 to (6)H13/2. The emission intensities of these compounds were found to be very sensitive to the phase.

Recycling antibiotics into GUMBOS: a new combination strategy to combat multi-drug-resistant bacteria.

The emergence of multi-drug-resistant bacteria, coupled with the lack of new antibiotics in development, is fast evolving into a global crisis. New strategies utilizing existing antibacterial agents are urgently needed. We propose one such strategy in which four outmoded ß-lactam antibiotics (ampicillin, carbenicillin, cephalothin and oxacillin) and a well-known antiseptic (chlorhexidine di-acetate) were fashioned into a group of uniform materials based on organic salts (GUMBOS) as an alternative to conventional combination drug dosing strategies. The antibacterial activity of precursor ions (e.g., chlorhexidine diacetate and ß-lactam antibiotics), GUMBOS and their unreacted mixtures were studied with 25 clinical isolates with varying antibiotic resistance using a micro-broth dilution method. Acute cytotoxicity and therapeutic indices were determined using fibroblasts, endothelial and cervical cell lines. Intestinal permeability was predicted using a parallel artificial membrane permeability assay. GUMBOS formed from ineffective ß-lactam antibiotics and cytotoxic chlorhexidine diacetate exhibited unique pharmacological properties and profound antibacterial activity at lower concentrations than the unreacted mixture of precursor ions at equivalent stoichiometry. Reduced cytotoxicity to invasive cell types commonly found in superficial and chronic wounds was also observed using GUMBOS. GUMBOS show promise as an alternative combination drug strategy for treating wound infections caused by drug-resistant bacteria.

Perspectives on moving ionic liquid chemistry into the solid phase.

Ionic liquid (IL) chemistry has evolved over the past century, such that these organic salts have impacted virtually every area of science and engineering. In the area of chemistry, initial applications of these salts were primarily the domain of chemists or chemical engineers who desired to manipulate the properties of IL solvents for a variety of applications including tuning various chemical processes. Since then, the chemistry of these organic salts has progressed such that changing an important property of a solvent (e.g., melting point or hydrophobicity) often involves simply altering the counterion of the organic salt. It is with this simplicity in mind that we have recently embarked upon the use of such chemistry to manipulate important properties of solid-phase ionic organic materials. To differentiate this chemistry from ionic liquid chemistry, we have coined the acronym GUMBOS (group of uniform materials based on organic salts). In this perspective article, we describe and demonstrate how ionic liquid chemistry can provide distinct and sometimes unique chemistry for solid-phase applications. Solid phase properties which can be manipulated via this chemistry include, but are not limited to, magnetism, melting point, hydrophobicity, fluorescence quantum yields, nanoformulations, material aggregation, viscosity, viscoelasticity, and cytotoxicity. In addition, we discuss a few examples to demonstrate how GUMBOS chemistry, until now, has been beneficial to the general area of materials chemistry and, more broadly, to the field of analytical chemistry. We also project future applications of this technology.

Surfactant-based ionic liquids for extraction of phenolic compounds combined with rapid quantification using capillary electrophoresis.

A rapid liquid phase extraction employing a novel hydrophobic surfactant-based room temperature ionic liquid (RTIL), tetrabutylphosphonium dioctyl sulfosuccinate ([4C4 P][AOT]), coupled with capillary electrophoretic-UV (CE-UV) detection is developed for removal and determination of phenolic compounds. The long-carbon-chain RTIL used is sparingly soluble in most solvents and can be used to replace volatile organic solvents. This fact, in combination with functional-surfactant-anions, is proposed to reduce the interfacial energy of the two immiscible liquid phases, resulting in highly efficient extraction of analytes. Several parameters that influence the extraction efficiencies, such as extraction time, RTIL type, pH value, and ionic strength of aqueous solutions, were investigated. It was found that, under acidic conditions, most of the investigated phenols were extracted from aqueous solution into the RTIL phase within 12 min. Good linearity was observed over the concentration range of 0.1-80.0 µg/mL for all phenols investigated. The precision of this method, expressed as RSD, was determined to be within 3.4-5.3% range. The LODs (S/N = 3) of the method were in the range of 0.047-0.257 µg/mL. The proposed methodology was successfully applied to determination of phenols in real water samples.

GUMBOS matrices of variable hydrophobicity for matrix-assisted laser desorption/ionization mass spectrometry.

RATIONALE: Detection of hydrophobic peptides remains a major obstacle for matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS). This stems from the fact that most matrices for MALDI are hydrophilic and therefore have low affinities for hydrophobic peptides. Herein, 1-aminopyrene (AP) and AP-derived group of uniform materials based on organic salts (GUMBOS) as novel matrices for MALDI-MS analyses of peptides were investigated for hydrophobic and hydrophilic peptides. METHODS: A number of solid-phase AP-based GUMBOS are synthesized with variable hydrophobicity simply by changing the counterions. Structures were confirmed by use of (1)H NMR and electrospray ionization mass spectrometry (ESI-MS). 1-Octanol/water partition coefficients (Ko/w) were used to measure the hydrophobicity of the matrices. A dried-droplet method was used for sample preparation. All spectra were obtained using a MALDI-TOF mass spectrometer in positive ion reflectron mode. RESULTS: A series of AP-based GUMBOS was synthesized including [AP][chloride] ([AP][Cl]), [AP][ascorbate] ([AP][Asc]) and [AP][bis(trifluoromethane)sulfonimide] ([AP][NTf2]). The relative hydrophobicities of these compounds and α-cyano-4-hydroxycinnamic acid (CHCA, a common MALDI matrix) indicated that AP-based GUMBOS can be tuned to be much more hydrophobic than CHCA. A clear trend is observed between the signal intensities of hydrophobic peptides and hydrophobicity of the matrix. CONCLUSIONS: MALDI matrices of GUMBOS with tunable hydrophobicities are easily obtained simply by varying the counterion. We have found that hydrophobic matrix materials are very effective for MALDI determination of hydrophobic peptides and, similarly, the more hydrophilic peptides displayed greater intensity in the more hydrophilic matrix.

In vitro activity studies of hyperthermal near-infrared nanoGUMBOS in MDA-MB-231 breast cancer cells.

A new kind of material called nanoGUMBOS, comprised entirely of cations and anions, has been developed by pairing various functional ions that exhibit fluorescence activity with biocompatible ions, in a process very much akin to that employed in ionic liquid chemistry. In the present study, spectral and biological properties of NIR absorbing nanoGUMBOS were evaluated using electron microscopy, dynamic light scattering, absorbance, thermal imaging, and live/dead fluorescence assays in conjunction with malignant MDA-MB-231 and non-malignant HS-578-BST epithelial human breast cells. The primary focus of this study was to maximize heat generation using NIR laser irradiation and minimize non-specific cytotoxicity using biocompatible constituent ions (e.g. amino acids, vitamins, or organic acids). Concurrently, in order to generate highly responsive nanomaterials for NIR-laser-triggered hyperthermia, optimization of the nanoparticle size, shape, and uniformity was carried out. Evaluation of data from hyperthermal studies of NIR absorbing nanoGUMBOS shows that these materials can achieve temperatures above the threshold for killing cancerous cells. Additionally, in vitro cell based assays demonstrated their promising hyperthermal effects on cancer derived epithelial cells.

Studies of Protein Binding to Biomimetic Membranes Using a Group of Uniform Materials Based on Organic Salts Derived From 8-Anilino-1-naphthalenesulfonic Acid.

Tuning the 8-anilino-1-naphthalenesulfonic acid (ANS) structure usually requires harsh conditions and long reaction times, which can result in low yields. Herein, ANS was modified to form an ANS group of uniform materials based on organic salts (GUMBOS), prepared with simple metathesis reactions and distinct cations, namely tetrabutylammonium (N4444), tetrahexylammonium (N6666), and tetrabutylphosphonium (P4444). These ANS-based GUMBOS were investigated as fluorescent probes for membrane binding studies with four proteins having distinct physicochemical properties. Liposomes of 1,2-dimyristoyl-sn-glycero-3-phosphocholine were employed as membrane models as a result of their ability to mimic the structure and chemical composition of cell membranes. Changes in fluorescence intensity were used to monitor protein binding to liposomes, and adsorption data were fitted to a Freundlich-like isotherm. It was determined that [N4444][ANS] and [P4444][ANS] GUMBOS have enhanced optical properties and lipophilicity as compared to parent ANS. As a result, these two GUMBOS were selected for subsequent protein-membrane binding studies. Both [N4444][ANS] and [P4444][ANS] GUMBOS and parent ANS independently reached membrane saturation within the same concentration range. Furthermore, distinct fluorescence responses were observed upon the addition of proteins to each probe, which demonstrates the impact of properties such as lipophilicity on the binding process. The relative maintenance of binding cooperativity and maximum fluorescence intensity suggests that proteins compete with ANS-based probes for the same membrane binding sites. Finally, this GUMBOS-based approach is simple, rapid, and involves relatively small amounts of reagents, making it attractive for high-throughput purposes. These results presented herein can also provide relevant information for designing GUMBOS with ameliorated properties.