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Victor S-Y Lin

Publications and source records attributed to Victor S-Y Lin.

17 recordsLinked to original sources
PubMed2006

Effect of surface functionalization of MCM-41-type mesoporous silica nanoparticles on the endocytosis by human cancer cells.

We have synthesized a series of MCM-41-type mesoporous silica nanoparticles (MSN). The surface of the MSNs are functionalized with 3-aminopropyl (AP), 3-guanidinopropyl (GP), 3-[N-(2-guanidinoethyl)guanidino]propyl (GEGP), and N-folate-3-aminopropyl (FAP). In contrast to the zeta-potential of -18.4 mV for FITC-MSN, the values of zeta-potential for AP-, GP-, GEGP-, and FAP-functionalized FITC-MSNs in 100 mM PBS buffer (pH 7.4) increased positively from -11.3, -10.6, -4.0, to +4.9 mV, respectively. The uptake efficiency, endocytosis mechanism, and biocompatibility of these organically functionalized MSNs were investigated with human cervical cancer cells (HeLa). Flow cytometry results suggested that the endocytosis of MSN could be manipulated by different surface functionalization. The immunocytochemistry study indicated that the uptake of these MSNs by HeLa cells was surface functional group dependent and involved several different mechanisms of endocytosis. Confocal fluorescence micrographs showed that the different surface functionalities of MSNs could also affect their ability to escape endosomal entrapment, which is a key factor in designing effective intracellular delivery vehicles.

Endocytosis↗
PubMed2005

Dialkylaminopyridine-functionalized mesoporous silica nanosphere as an efficient and highly stable heterogeneous nucleophilic catalyst.

A new nucleophilic catalytic system comprised of dialkylaminopyridine-functionalized mesoporous silica nanosphere (DMAP-MSN) has been synthesized and characterized. We have demonstrated that this material is an efficient heterogeneous catalyst for Baylis-Hillman, acylation, and silylation reactions with good reactivity, product selectivity, and recyclability. We envision that this DMAP-functionalized mesoporous silica material can also serve as an effective heterogeneous catalyst for many other catalytic nucleophilic reactions.

Aminopyridines↗
PubMed2005

Mesoporous silica-supported uranyl: synthesis and photoreactivity.

A mesoporous silica-supported uranyl material (U(aq)O(2)(2+)-silica) was prepared by a co-condensation method. Our approach involves an I(-)M(+)S(-) scheme, where the electrostatic interaction between the anionic inorganic precursor (I(-)), surfactant (S(-)), and cationic mediator (M(+)) provides the basis for the stability of the composite material. The synthesis was carried out under acidic conditions, where the anionic sodium dodecyl sulfate provided the template for the uranyl cation and silicate to condense. Excitation with visible or near-UV light of aqueous suspensions of U(aq)O(2)(2+)-silica generates an excited state that decays with k(0) = 1.5 x 10(4) s(-1). The reaction of the excited state with aliphatic alcohols exhibits kinetic saturation and concentration-dependent kinetic isotope effects. For 2-propanol, the value of k(C)3(H)7(OH)/k(C)()3(D)7(OH) decreases from 2.0 at low alcohol concentrations to 1.0 in the saturation regime at high alcohol concentrations. Taken together, the data describe a kinetic system controlled by chemical reaction at one extreme and diffusion at the other. At low [alcohol], the second-order rate constants for the reaction of silica-U(aq)O(2)(2+) with methanol, 2-propanol, 2-butanol, and 2-pentanol are comparable to the rate constants obtained for these alcohols in homogeneous aqueous solutions containing H(3)PO(4). Under slow steady-state photolysis in O(2)-saturated suspensions, U(aq)O(2)(2+)-silica acts as a photocatalyst for the oxidation of alcohols with O(2).

Journal Article↗
PubMed2005

Hyperpolarized 129Xe NMR investigation of multifunctional organic/inorganic hybrid mesoporous silica materials.

An extensive study has been made on a series of multifunctional mesoporous silica materials, prepared by introducing two different organoalkoxysilanes, namely 3-[2-(2-aminoethylamino)ethylamino]propyltrimethoxysilane (AEPTMS) and 3-cyanopropyltriethoxysilane (CPTES) during the base-catalyzed condensation of tetraethoxysilane (TEOS), using the variable-temperature (VT) hyperpolarized (HP) 129Xe NMR technique. VT HP-129Xe NMR chemical shift measurements of adsorbed xenon revealed that surface properties as well as functionality of these AEP/CP-functionalized microparticles (MP) could be controlled by varying the AEPTMS/CPTES ratio in the starting solution during synthesis. Additional chemical shift contribution due to Xe-moiety interactions was observed for monofunctional AEP-MP and CP-MP as well as for bifunctional AEP/CP-MP samples. In particular, unlike CP-MP that has a shorter organic backbone on the silica surface, the amino groups in the AEP chain tends to interact with the silanol groups on the silica surface causing backbone bending and hence formation of secondary pores in AEP-MP, as indicated by additional shoulder peak at lower field in the room-temperature 129Xe NMR spectrum. The exchange processes of xenon in different adsorption regions were also verified by 2D EXSY HP-129Xe NMR spectroscopy. It is also found that subsequent removal of functional moieties by calcination treatment tends to result in a more severe surface roughness on the pore walls in bifunctional samples compared to monofunctional ones. The effect of hydrophobicity/hydrophilicity of the organoalkoxysilanes on the formation, pore structure and surface property of these functionalized mesoporous silica materials are also discussed.

Inorganic Chemicals↗
PubMed2005

Studies of organically functionalized mesoporous silicas using heteronuclear solid-state correlation NMR spectroscopy under fast magic angle spinning.

Highly resolved solid-state HETCOR NMR spectra between protons and low gamma nuclei ((13)C and (29)Si) can be suitably obtained on surfaces using a "brute force" (1)H-(1)H decoupling by MAS at rates > or =40 kHz. Despite a small rotor volume (<10 microL), a (1)H-(13)C HETCOR spectrum of allyl groups (AL, -CH(2)-CH=CH(2)) covalently anchored to the surface of MCM-41 silica was acquired without using isotope enrichment. The advantages of using fast MAS in such studies include easy setup, robustness, and the opportunity of using low RF power for decoupling. In the case of the (1)H-(29)Si HETCOR experiment, the sensitivity can be dramatically increased, in some samples by more than 1 order of magnitude, through implementing into the pulse sequence a Carr-Purcell-Meiboom-Gill train of pi pulses at the (29)Si spin frequency. The use of low-power heteronuclear decoupling is essential in the (1)H-(29)Si CPMG-HETCOR experiment, due to unusually long acquisition periods. These methods provided detailed structural characterization of the surface of AL-MCM mesoporous silica.

Journal Article↗
PubMed2005

Solid-state NMR study of MCM-41-type mesoporous silica nanoparticles.

A systematic study of the surface of MCM-41-type mesoporous silica nanoparticles prepared under low surfactant concentration was carried out using high-resolution solid-state nuclear magnetic resonance spectroscopy. The structures and concentrations of various species present during dehydration and rehydration of mesoporous silicas between -25 and 500 degrees C were detailed by employing one-dimensional and two-dimensional (1)H, (13)C, and (29)Si NMR, including (1)H signal intensity measurements, (1)H-(1)H homonuclear correlation experiments (double quantum, exchange, and RFDR), and (1)H-(29)Si heteronuclear correlation NMR. These experiments employed high MAS rates of up to 45 kHz. The study shows that the surfactant (CTAB) was almost completely removed by acid extraction. The residual molecules assumed prone positions along the pores, with the tailgroup being most mobile. The weakly adsorbed water was hydrogen bonded to the silanol groups, all of which were involved in such bonds under ambient humidity. Specific structures involving water and silanol groups were proposed for various stages of thermal treatment, which included dehydration, dehydroxylation, and subsequent rehydration.

Journal Article↗
PubMed2005

Real-time imaging of tunable adenosine 5-triphosphate release from an MCM-41-type mesoporous silica nanosphere-based delivery system.

We studied a mesoporous silica nanosphere (MSN) material with tunable release capability for drug delivery applications. We employed luciferase chemiluminescence imaging to investigate the kinetics and mechanism of the adenosine 5-triphosphate (ATP) release with various disulfide-reducing agents as uncapping triggers. ATP molecules were encapsulated within the MSNs by immersing dry nanospheres in aqueous solutions of ATP followed by capping of the mesopores with chemically removable caps, such as cadmium sulfide (CdS) nanoparticles and poly(amido amine) dendrimers (PAMAM), via a disulfide linkage. By varying the chemical nature of the ''cap'' and ''trigger'' molecules in our MSN system, we discovered that the release profiles could indeed be regulated in a controllable fashion.

Adenosine Triphosphate↗
PubMed2004

Fine-tuning the degree of organic functionalization of mesoporous silica nanosphere materials via an interfacially designed co-condensation method.

A synthetic method that can fine tune the amount of chemically accessible organic functional groups on the pore surface of MCM-41 type mesoporous silica nanosphere (MSN) materials has been developed by electrostatically matching various anionic organoalkoxysilanes with the cationic cetyltrimethylammonium bromide micelles in a base-catalyzed condensation reaction of tetraethoxysilane.

Anions↗
PubMed2004

Encapsulation, stabilization, and release of BSA-FITC from polyanhydride microspheres.

In order to determine the efficacy of using polyanhydrides as a carrier for therapeutic proteins, the model protein bovine serum albumin labeled with fluorescein isothiocyanate (BSA-FITC) was encapsulated in microspheres of poly sebacic anhydride (poly(SA)), and random copolymers of poly(SA) and poly(1,6-bis-p-carboxyphenoxy)hexane (poly(CPH)). The microspheres were fabricated via the double emulsion (water/oil/water) technique and were characterized using scanning electron microscopy, gel permeation chromatography, confocal microscopy, and a Coulter counter. The effect of protein loading, protein distribution, and change in polymer composition was examined in an in vitro release study. The secondary structure of the encapsulated BSA-FITC was determined with Fourier transform infrared spectroscopy. The primary structure of the released protein was analyzed using sodium dodecyl sulfate polyacrylamide gel electrophoresis. Poly(SA) and 20:80 (CPH:SA) microspheres were found to conserve the primary structure of the released protein and the secondary structure of the encapsulated protein, and showed a sustained delivery for approximately 15 and 30 days, respectively. As the CPH content in the copolymer increased, the secondary structure of FITC-BSA was not conserved, as indicated by the steep decrease in the alpha-helix content.

Electrophoresis, Polyacrylamide Gel↗
PubMed2004

A polyamidoamine dendrimer-capped mesoporous silica nanosphere-based gene transfection reagent.

We synthesized a MCM-41-type mesoporous silica nanosphere (MSN)-based gene transfection system, where second generation (G2) polyamidoamines (PAMAMs) were covalently attached to the surface of MSN. The G2-PAMAM-capped MSN material (G2-MSN) was used to complex with a plasmid DNA (pEGFP-C1) that encodes for an enhanced green fluorescence protein. The gene transfection efficacy, uptake mechanism, and biocompatibility of the G2-MSN system with various cell types, such as neural glia (astrocytes), human cervical cancer (HeLa), and Chinese hamster ovarian (CHO) cells, were investigated. The mesoporous structure of the MSN material allows membrane-impermeable molecules, such as pharmaceutical drugs and fluorescent dyes, to be encapsulated inside the MSN channels. The system renders the possibility to serve as a universal transmembrane carrier for intracellular drug delivery and imaging applications.

Animals↗
PubMed2004

Gatekeeping layer effect: a poly(lactic acid)-coated mesoporous silica nanosphere-based fluorescence probe for detection of amino-containing neurotransmitters.

We have synthesized a poly(lactic acid) coated MCM-41-type mesoporous silica nanosphere (PLA-MSN) material can serve as a fluorescence sensor system for detection of amino-containing neurotransmitters in neutral aqueous buffer. Utilizing the PLA layer as a gatekeeper, we investigated the molecular recognition events between several structurally simple neurotransmitters, i.e., dopamine, tyrosine, and glutamic acid and a pore surface-anchored o-phthalic hemithioacetal (OPTA) group, which functions as a fluorescence-sensing group that can react with the neurotransmitters with primary amine groups and form the corresponding fluorescent isoindole products. The poly(lactic acid) layer of the PLA-MSN sensor showed a unique "sieving" effect that regulates the rates of diffusion of the amino acid-based neurotransmitters into the sensor mesopores of the material.

Acetals↗
PubMed2004

Controlling the selectivity of competitive nitroaldol condensation by using a bifunctionalized mesoporous silica nanosphere-based catalytic system.

A series of bifunctionalized mesoporous silica nanosphere-based (MSN) heterogeneous catalysts for the nitroaldol (Henry) reaction have been synthesized. A common 3-[2-(2-aminoethylamino)ethylamino]propyl (AEP) primary group and three different secondary groups, ureidopropyl (UDP), mercaptopropyl (MP), and allyl (AL) functionalities, were incorporated to these mesoporous silica materials by introducing equal amounts of AEP-trimethoxysilane with UDP-, MP-, or AL-trialkoxysilane precursors to our previously reported co-condensation reaction. Structures and relative concentrations of the functional groups were detailed by solid-state NMR and other spectroscopic techniques. The AEP group served as a catalyst, and the other secondary groups provided different noncovalent interactions to reactants and thereby controlled the reaction selectivity. By varying the secondary group in these bifunctionalized MSN catalysts, we investigated the selectivity of a nitroaldol reaction of two competing benzaldehydes reacting with nitromethane by measuring the molar ratio of the nitroalkene products. The selectivity of the bifunctionalized MSN catalysts could be systematically tuned simply by varying the physicochemical properties of the pore surface-bound secondary groups, i.e., polarity and hydrophobicity.

Journal Article↗
PubMed2003

A mesoporous silica nanosphere-based carrier system with chemically removable CdS nanoparticle caps for stimuli-responsive controlled release of neurotransmitters and drug molecules.

An MCM-41 type mesoporous silica nanosphere-based (MSN) controlled-release delivery system has been synthesized and characterized using surface-derivatized cadmium sulfide (CdS) nanocrystals as chemically removable caps to encapsulate several pharmaceutical drug molecules and neurotransmitters inside the organically functionalized MSN mesoporous framework. We studied the stimuli-responsive release profiles of vancomycin- and adenosine triphosphate (ATP)-loaded MSN delivery systems by using disulfide bond-reducing molecules, such as dithiothreitol (DTT) and mercaptoethanol (ME), as release triggers. The biocompatibility and delivery efficiency of the MSN system with neuroglial cells (astrocytes) in vitro were demonstrated. In contrast to many current delivery systems, the molecules of interest were encapsulated inside the porous framework of the MSN not by adsorption or sol-gel types of entrapment but by capping the openings of the mesoporous channels with size-defined CdS nanoparticles to physically block the drugs/neurotransmitters of certain sizes from leaching out. We envision that this new MSN system could play a significant role in developing new generations of site-selective, controlled-release delivery nanodevices.

Adenosine Triphosphate↗
PubMed2003

DNA-based photonic logic gates: AND, NAND, and INHIBIT.

Conventional microprocessors use elementary logic gates to perform complex computational tasks. Mimicking such computational processes using purely molecular systems has been limited in most cases by the lack of design generality or potential addressability of existing molecular logic gates. Herein we report that by employing the universal recognition properties of DNA simple photonic logic gates can be created that are capable of AND, NAND, and INHIBIT logic operations.

Computational Biology↗
PubMed2002

Oxidative polymerization of 1,4-diethynylbenzene into highly conjugated poly(phenylene butadiynylene) within the channels of surface-functionalized mesoporous silica and alumina materials.

A polyalkynylene-based conducting polymer (molecular wire) has been synthesized within the Cu-functionalized mesoporous MCM-41 silica catalyst. Fluorescence and 13C solid-state NMR provided spectroscopic evidence that the synthesis of extended polymeric chains with a high degree of alignment requires homogeneously distributed catalytic sites throughout the entire MCM matrix. This type of homogeneity has been achieved via co-condensation of the catalytic groups in narrow pores. In addition, our results indicated that proper adjustment of the pore diameter is vital to prevent clogging of the pores with aggregated or cross-linked polymers or both.

Journal Article↗