Chemical communications (Cambridge, England), Jan 14, 2016
Biodegradable conjugated polymer nanoparticles (CPNs) were prepared for high mitochondrial target... more Biodegradable conjugated polymer nanoparticles (CPNs) were prepared for high mitochondrial targeting in live cancer cells. The degradable CPNs are nontoxic and specifically localized to the mitochondria of live tumor cells through macropinocytosis followed by intracellular degradation and trafficking.
Understanding and controlling aggregation structures of conjugated polymers (CPs) in aqueous solu... more Understanding and controlling aggregation structures of conjugated polymers (CPs) in aqueous solutions is critical to improving the physical and photophysical properties of CPs for biological applications. Here, we present spectroscopic evidence, including nuclear magnetic resonance (NMR) spectroscopic results, that different organic acid treatment induces different aggregation structures and photophysical properties of CPs in water. Conjugated polymer nanoparticles (CPNs) were fabricated by treating a non-aqueous soluble, primary amine-containing poly(phenylene ethynylene) (PPE-NH(2)) with organic acids followed by dialysis. CPNs formed by acetic acid (AA) treatment (CPN-AAs) exhibit characteristics of loose aggregation with minimal π-π stacking, while CPNs formed by tartaric acid (TA) treatment (CPN-TAs) exhibit a high degree of π-π stacking among PPE-NH(2) chains. The controlled aggregation for a specific application was demonstrated by comparing the fluorescence quenching abilities of the CPN-AAs and the CPN-TAs. A doubled Stern-Volmer constant was obtained from the densely packed CPN-TAs compared to that of the loosely aggregated CPN-AAs.
Core-shell conjugated polymer nanoparticles (CPNs) were fabricated by complexing a semi-flexible,... more Core-shell conjugated polymer nanoparticles (CPNs) were fabricated by complexing a semi-flexible, primary amine-containing conjugated polymer (CP) with hyaluronic acid (HA). Flexibility introduced in the rigid rod conjugated backbone allows backbone reorganization to increase π-π interaction under ionic complexation, resulting in core-shell nanoparticles with a hydrophobic CP core wrapped with a HA shell. The core-shell nanoparticles exhibited no cellular toxicity and high cancer cell specificity with minimal binding to normal cells.
Previous work has demonstrated the ability to differentiate individuals based on the analysis of ... more Previous work has demonstrated the ability to differentiate individuals based on the analysis of human scent hand odor chemicals. In this paper, a range of forensic biological specimens are shown to also have the ability to differentiate individuals based upon the volatile organic compounds (VOCs) present. Human VOC profiles from hand odor, oral fluid, breath, blood, and urine of 31 individuals were analyzed by solid-phase microextraction-gas chromatography-mass spectrometry (SPME-GC-MS) and combined methods of chromatogram comparison, Spearman rank correlation comparison, and principal component analysis. Intra-specimen comparisons demonstrated the distinguishability of individuals above 99%. Inter-specimen VOC profiles from the same individual were found to be too different to be used for scent-matching purposes, with Spearman rank coefficients below 0.15. A 6-month VOC profile monitoring of two individuals demonstrated the consistency of VOC profiles over time across specimens.
Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2013
ABSTRACT Although physicochemical processes at liquid/solid boundaries are critical in several in... more ABSTRACT Although physicochemical processes at liquid/solid boundaries are critical in several increasingly important areas of environmental science and engineering, research methods used to contact solutes and adsorbents have changed little in recent decades. We describe an emerging liquid chromatographic (LC) experimental approach which can be used to investigate various phenomena at liquid/solid boundaries, and we report its application in studies of Suwannee River Humic Acid (SRHA) adsorptive fractionation and phosphate competitive displacement on aluminum oxide coated quartz (AlQ). This LC-based approach is similar to continuous-flow column (i.e., breakthrough) methods. However, using the LC auto-injection system, `pulsed' (i.e., non-continuous) additions of adsorbate (or displacement agent) are made onto adsorbent-packed columns, and non-adsorbed (or displaced) ligands are monitored in multiple optical chromatographic detection channels. We applied the LC-based method in this area of research because (i) this method promises to be more efficient (in materials and analytical/experimental time) than conventional (batch and continuous-flow column) methods, and (ii) it generates unique data that reveal changes in of solution-phase adsorbate mixture compositions due to preferential adsorption or displacement effects. In an SRHA-AlQ adsorption study, detector signal ratios suggested preferential adsorption of high molecular weight (MW) SRHA constituents. When phosphate ions reacted with SRHA-saturated AlQ surfaces, these ratios indicated preferential displacement of low MW SRHA constituents. Adsorption and displacement results agreed, indicating relatively high MW SRHA constituents bound with greatest affinity. Results agree with previous studies of similar adsorbate–adsorbent systems conducted using conventional methods, which validates this method. Each of these experiments, which provided data on both adsorptive fractionation and competitive displacement, was completed in the timeframe of a typical chromatographic experiment and consumed <1 mg adsorbate and < 2 g adsorbent. Based on its temporal and materials efficiencies and its ability to yield unique forms of data pertaining to the interactions of complex organic ligand mixtures with adsorbent surfaces, this LC-based method will be an important alternative and/or complementary technique that will provide new insights into the interplay of processes that ultimately govern humic substances adsorption.
The subcellular localization and toxicity of conjugated polymer nanoparticles (CPNs) are dependen... more The subcellular localization and toxicity of conjugated polymer nanoparticles (CPNs) are dependent on the chemical structure of the side chains and backbone. Primary amine-containing CPNs exhibit high Golgi localization with no toxicity. Incorporation of short ethylene oxide and tertiary amine side chains contributes to decreased Golgi localization and increased toxicity, respectively.
Loosely aggregated conjugated polymer nanoparticles (CPNs) were used as nontoxic and efficient sm... more Loosely aggregated conjugated polymer nanoparticles (CPNs) were used as nontoxic and efficient small interfering RNA (siRNA) delivery vehicles with delivery visualization. A significant down regulation (94%) of a target gene was achieved by transfection of HeLa cells with the CPNs/siRNA complexes, supporting CPN as a promising siRNA delivery carrier.
Chemical communications (Cambridge, England), Jan 14, 2016
Biodegradable conjugated polymer nanoparticles (CPNs) were prepared for high mitochondrial target... more Biodegradable conjugated polymer nanoparticles (CPNs) were prepared for high mitochondrial targeting in live cancer cells. The degradable CPNs are nontoxic and specifically localized to the mitochondria of live tumor cells through macropinocytosis followed by intracellular degradation and trafficking.
Understanding and controlling aggregation structures of conjugated polymers (CPs) in aqueous solu... more Understanding and controlling aggregation structures of conjugated polymers (CPs) in aqueous solutions is critical to improving the physical and photophysical properties of CPs for biological applications. Here, we present spectroscopic evidence, including nuclear magnetic resonance (NMR) spectroscopic results, that different organic acid treatment induces different aggregation structures and photophysical properties of CPs in water. Conjugated polymer nanoparticles (CPNs) were fabricated by treating a non-aqueous soluble, primary amine-containing poly(phenylene ethynylene) (PPE-NH(2)) with organic acids followed by dialysis. CPNs formed by acetic acid (AA) treatment (CPN-AAs) exhibit characteristics of loose aggregation with minimal π-π stacking, while CPNs formed by tartaric acid (TA) treatment (CPN-TAs) exhibit a high degree of π-π stacking among PPE-NH(2) chains. The controlled aggregation for a specific application was demonstrated by comparing the fluorescence quenching abilities of the CPN-AAs and the CPN-TAs. A doubled Stern-Volmer constant was obtained from the densely packed CPN-TAs compared to that of the loosely aggregated CPN-AAs.
Core-shell conjugated polymer nanoparticles (CPNs) were fabricated by complexing a semi-flexible,... more Core-shell conjugated polymer nanoparticles (CPNs) were fabricated by complexing a semi-flexible, primary amine-containing conjugated polymer (CP) with hyaluronic acid (HA). Flexibility introduced in the rigid rod conjugated backbone allows backbone reorganization to increase π-π interaction under ionic complexation, resulting in core-shell nanoparticles with a hydrophobic CP core wrapped with a HA shell. The core-shell nanoparticles exhibited no cellular toxicity and high cancer cell specificity with minimal binding to normal cells.
Previous work has demonstrated the ability to differentiate individuals based on the analysis of ... more Previous work has demonstrated the ability to differentiate individuals based on the analysis of human scent hand odor chemicals. In this paper, a range of forensic biological specimens are shown to also have the ability to differentiate individuals based upon the volatile organic compounds (VOCs) present. Human VOC profiles from hand odor, oral fluid, breath, blood, and urine of 31 individuals were analyzed by solid-phase microextraction-gas chromatography-mass spectrometry (SPME-GC-MS) and combined methods of chromatogram comparison, Spearman rank correlation comparison, and principal component analysis. Intra-specimen comparisons demonstrated the distinguishability of individuals above 99%. Inter-specimen VOC profiles from the same individual were found to be too different to be used for scent-matching purposes, with Spearman rank coefficients below 0.15. A 6-month VOC profile monitoring of two individuals demonstrated the consistency of VOC profiles over time across specimens.
Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2013
ABSTRACT Although physicochemical processes at liquid/solid boundaries are critical in several in... more ABSTRACT Although physicochemical processes at liquid/solid boundaries are critical in several increasingly important areas of environmental science and engineering, research methods used to contact solutes and adsorbents have changed little in recent decades. We describe an emerging liquid chromatographic (LC) experimental approach which can be used to investigate various phenomena at liquid/solid boundaries, and we report its application in studies of Suwannee River Humic Acid (SRHA) adsorptive fractionation and phosphate competitive displacement on aluminum oxide coated quartz (AlQ). This LC-based approach is similar to continuous-flow column (i.e., breakthrough) methods. However, using the LC auto-injection system, `pulsed' (i.e., non-continuous) additions of adsorbate (or displacement agent) are made onto adsorbent-packed columns, and non-adsorbed (or displaced) ligands are monitored in multiple optical chromatographic detection channels. We applied the LC-based method in this area of research because (i) this method promises to be more efficient (in materials and analytical/experimental time) than conventional (batch and continuous-flow column) methods, and (ii) it generates unique data that reveal changes in of solution-phase adsorbate mixture compositions due to preferential adsorption or displacement effects. In an SRHA-AlQ adsorption study, detector signal ratios suggested preferential adsorption of high molecular weight (MW) SRHA constituents. When phosphate ions reacted with SRHA-saturated AlQ surfaces, these ratios indicated preferential displacement of low MW SRHA constituents. Adsorption and displacement results agreed, indicating relatively high MW SRHA constituents bound with greatest affinity. Results agree with previous studies of similar adsorbate–adsorbent systems conducted using conventional methods, which validates this method. Each of these experiments, which provided data on both adsorptive fractionation and competitive displacement, was completed in the timeframe of a typical chromatographic experiment and consumed <1 mg adsorbate and < 2 g adsorbent. Based on its temporal and materials efficiencies and its ability to yield unique forms of data pertaining to the interactions of complex organic ligand mixtures with adsorbent surfaces, this LC-based method will be an important alternative and/or complementary technique that will provide new insights into the interplay of processes that ultimately govern humic substances adsorption.
The subcellular localization and toxicity of conjugated polymer nanoparticles (CPNs) are dependen... more The subcellular localization and toxicity of conjugated polymer nanoparticles (CPNs) are dependent on the chemical structure of the side chains and backbone. Primary amine-containing CPNs exhibit high Golgi localization with no toxicity. Incorporation of short ethylene oxide and tertiary amine side chains contributes to decreased Golgi localization and increased toxicity, respectively.
Loosely aggregated conjugated polymer nanoparticles (CPNs) were used as nontoxic and efficient sm... more Loosely aggregated conjugated polymer nanoparticles (CPNs) were used as nontoxic and efficient small interfering RNA (siRNA) delivery vehicles with delivery visualization. A significant down regulation (94%) of a target gene was achieved by transfection of HeLa cells with the CPNs/siRNA complexes, supporting CPN as a promising siRNA delivery carrier.
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Papers by Eladio Mendez