Publications by authors named "Rian You"

5 Publications

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Surface Modification of Cisplatin-Complexed Gold Nanoparticles and Its Influence on Colloidal Stability, Drug Loading, and Drug Release.

Langmuir 2018 Jan 18;34(1):154-163. Epub 2017 Dec 18.

University of Maryland, College Park, Maryland 20742, United States.

Cisplatin-complexed gold nanoparticles (Pt-AuNP) provide a promising strategy for chemo-radiation-based anticancer drugs. Effective design of such platforms necessitates reliable assessment of surface engineering on a quantitative basis and its influence on drug payload, stability, and release. In this paper, poly(ethylene glycol) (PEG)-stabilized Pt-AuNP was synthesized as a model antitumor drug platform, where Pt is attached via a carboxyl-terminated dendron ligand. Surface modification by PEG and its influence on drug loading, colloidal stability, and drug release were assessed. Complexation with Pt significantly degrades colloidal stability of the conjugate; however, PEGylation provides substantial improvement of stability in conjunction with an insignificant trade-off in drug loading capacity compared with the non-PEGylated control (<20% decrease in loading capacity). In this context, the effect of varying PEG concentration and molar mass was investigated. On a quantitative basis, the extent of PEGylation was characterized and its influence on dispersion stability and drug load was examined using electrospray differential mobility analysis (ES-DMA) hyphenated with inductively coupled plasma mass spectrometry (ICP-MS) and compared with attenuated total reflectance-FTIR. Using ES-DMA-ICP-MS, AuNP conjugates were size-classified based on their electrical mobility, while Pt loading was simultaneously quantified by determination of Pt mass. Colloidal stability was quantitatively evaluated in biologically relevant media. Finally, the pH-dependent Pt release performance was evaluated. We observed 9% and 16% Pt release at drug loadings of 0.5 and 1.9 Pt/nm, respectively. The relative molar mass of PEG had no significant influence on Pt uptake or release performance, while PEGylation substantially improved the colloidal stability of the conjugate. Notably, the Pt release over 10 days (examined at 0.5 Pt/nm drug loading) remained constant for non-PEGylated, 1K-PEGylated, and 5K-PEGylated conjugates.
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http://dx.doi.org/10.1021/acs.langmuir.7b02354DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6057618PMC
January 2018

Direct In Situ Mass Specific Absorption Spectra of Biomass Burning Particles Generated from Smoldering Hard and Softwoods.

Environ Sci Technol 2017 May 4;51(10):5622-5629. Epub 2017 May 4.

Material Measurement Laboratory, National Institute of Standards and Technology , Gaithersburg, Maryland 20899, United States.

Particles from smoldering biomass burning (BB) represent a major source of carbonaceous aerosol in the terrestrial atmosphere. In this study, mass specific absorption spectra of laboratory-generated smoldering wood particles (SWP) from 3 hardwood and 3 softwood species were measured in situ. Absorption data spanning from λ = 500 to 840 nm were collected using a photoacoustic spectrometer coupled to a supercontinuum laser with a tunable wavelength and bandwidth filter. SWP were size- (electrical mobility) and mass-selected prior to optical characterization allowing data to be reported as mass-specific absorption cross sections (MAC). The median measured MAC at λ = 660 nm for smoldering oak particles was 1.1 (0.57/1.8) × 10 m g spanning from 83 femtograms (fg) to 517 fg (500 nm ≤ mobility diameter ≤950 nm), MAC values in parentheses are the 16 and 84 percentiles of the measured data (i.e., 1σ). The collection of all six wood species (Oak, Hickory, Mesquite, Western redcedar, Baldcypress, and Blue spruce) had median MAC values ranging from 1.4 × 10 m g to 7.9 × 10 m g at λ = 550 nm with absorption Ångström exponents (AAE) between 3.5 and 6.2. Oak, Western redcedar, and Blue spruce possessed statistically similar (p > 0.05) spectra while the spectra of Hickory, Mesquite, and Baldcypress were distinct (p < 0.01) as calculated from a point-by-point analysis using the Wilcox rank-sum test.
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http://dx.doi.org/10.1021/acs.est.7b00810DOI Listing
May 2017

Measured Wavelength-Dependent Absorption Enhancement of Internally Mixed Black Carbon with Absorbing and Nonabsorbing Materials.

Environ Sci Technol 2016 08 14;50(15):7982-90. Epub 2016 Jul 14.

Material Measurement Laboratory, National Institute of Standards and Technology , Gaithersburg, Maryland 20899, United States.

Optical absorption spectra of laboratory generated aerosols consisting of black carbon (BC) internally mixed with nonabsorbing materials (ammonium sulfate, AS, and sodium chloride, NaCl) and BC with a weakly absorbing brown carbon surrogate derived from humic acid (HA) were measured across the visible to near-IR (550 to 840 nm). Spectra were measured in situ using a photoacoustic spectrometer and step-scanning a supercontinuum laser source with a tunable wavelength and bandwidth filter. BC had a mass-specific absorption cross section (MAC) of 7.89 ± 0.25 m(2) g(-1) at λ = 550 nm and an absorption Ångström exponent (AAE) of 1.03 ± 0.09 (2σ). For internally mixed BC, the ratio of BC mass to the total mass of the mixture was chosen as 0.13 to mimic particles observed in the terrestrial atmosphere. The manner in which BC mixed with each material was determined from transmission electron microscopy (TEM). AS/BC and HA/BC particles were fully internally mixed, and the BC was both internally and externally mixed for NaCl/BC particles. The AS/BC, NaCl/BC, and HA/BC particles had AAEs of 1.43 ± 0.05, 1.34 ± 0.06, and 1.91 ± 0.05, respectively. The observed absorption enhancement of mixed BC relative to the pure BC was wavelength dependent for AS/BC and decreased from 1.5 at λ = 550 nm with increasing wavelength while the NaCl/BC enhancement was essentially wavelength independent. For HA/BC, the enhancement ranged from 2 to 3 and was strongly wavelength dependent. Removal of the HA absorption contribution to enhancement revealed that the enhancement was ≈1.5 and independent of wavelength.
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http://dx.doi.org/10.1021/acs.est.6b01473DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5501421PMC
August 2016

Packing density of rigid aggregates is independent of scale.

Proc Natl Acad Sci U S A 2014 Jun 9;111(25):9037-41. Epub 2014 Jun 9.

Material Measurement Laboratory, National Institute of Standards and Technology, Gaithersburg, MD 20899; andDepartment of Chemical and Biomolecular Engineering, University of Maryland, College Park, MD 20742.

Large planetary seedlings, comets, microscale pharmaceuticals, and nanoscale soot particles are made from rigid, aggregated subunits that are compacted under low compression into larger structures spanning over 10 orders of magnitude in dimensional space. Here, we demonstrate that the packing density (θf) of compacted rigid aggregates is independent of spatial scale for systems under weak compaction. The θf of rigid aggregated structures across six orders of magnitude were measured using nanoscale spherical soot aerosol composed of aggregates with ∼ 17-nm monomeric subunits and aggregates made from uniform monomeric 6-mm spherical subunits at the macroscale. We find θf = 0.36 ± 0.02 at both dimensions. These values are remarkably similar to θf observed for comet nuclei and measured values of other rigid aggregated systems across a wide variety of spatial and formative conditions. We present a packing model that incorporates the aggregate morphology and show that θf is independent of both monomer and aggregate size. These observations suggest that the θf of rigid aggregates subject to weak compaction forces is independent of spatial dimension across varied formative conditions.
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http://dx.doi.org/10.1073/pnas.1403768111DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4078842PMC
June 2014

Dependence of soot optical properties on particle morphology: measurements and model comparisons.

Environ Sci Technol 2014 Mar 27;48(6):3169-76. Epub 2014 Feb 27.

Material Measurement Laboratory, National Institute of Standards and Technology , Gaithersburg, Maryland 20899, United States.

We report the first mass-specific absorption and extinction cross sections for size- and mass-selected laboratory-generated soot aerosol. Measurement biases associated with aerosols possessing multiple charges were eliminated using mass selection to isolate singly charged particles for a specified electrical mobility diameter. Aerosol absorption and extinction coefficients were measured using photoacoustic and cavity ring-down spectroscopy techniques, respectively, for lacey and compacted soot morphologies. The measurements show that the mass-specific absorption cross sections are proportional to particle mass and independent of morphology, with values between 5.7 and 6 m(2) g(-1). Mass-specific extinction cross sections were morphology dependent and ranged between 12 and 16 m(2) g(-1) for the lacey and compact morphologies, respectively. The resulting single-scattering albedos ranged from 0.5 to 0.6. Results are also compared to theoretical calculations of light absorption and scattering from simulated particle agglomerates. The observed absorption is relatively well modeled, with minimum differences between the calculated and measured mass absorption cross sections ranging from ∼ 5% (lacey soot) to 14% (compact soot). The model, however, was unable to satisfactorily reproduce the measured extinction, underestimating the single-scattering albedo for both particle morphologies. These discrepancies between calculations and measurements underscore the need for validation and refinement of existing models of light scattering and absorption by soot agglomerates.
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http://dx.doi.org/10.1021/es4041804DOI Listing
March 2014