shyam kadali - Academia.edu (original) (raw)
Papers by shyam kadali
Topics in Catalysis, May 30, 2008
A non-surfactant-based synthesis approach to mesoporous hollow spheres through the use of colloid... more A non-surfactant-based synthesis approach to mesoporous hollow spheres through the use of colloidal silica is presented. Based on nanoparticle assembly chemistry developed previously for silica/polymer hybrid microcapsules, the room-temperature preparation follows a two-step sequence: (1) the electrostatic reaction of cationic polymer with an anionic salt solution, resulting in a suspension of salt-bridged polymer aggregates; and (2) the electrostatic reaction between this suspension and an aqueous suspension of nanoparticles (NPs). As a specific example, 13-nm silica particles, combined with polyallylamine and sodium citrate, gave silica/polymer hollow spheres with a mean diameter of 2.1 lm and a BET surface area of 4 m 2 /g. After calcination at 600°C, the resulting silica-only microcapsules had a BET surface area of 259 m 2 /g, a modal pore size of 4.0 nm, and a pore volume of 0.38 cc/g, values that exceeded those of calcined silica NPs. This colloidal silica-based material is an example of the simultaneous control of pore size (at the nanometer scale) and particle morphology (at the micrometer scale) that is possible through charge-driven NP assembly.
ACS Applied Materials & Interfaces, Feb 20, 2009
Chemistry of Materials, Dec 29, 2010
Organic/inorganic composite microcapsules can be produced in water through a two-step chargedrive... more Organic/inorganic composite microcapsules can be produced in water through a two-step chargedriven assembly of polyallylamine, citrate anions, and 13 nm silica nanoparticles. The shell is composed of nanoparticles intermixed with polymer, and is thick enough (100s of nm) to provide structural stability before or after drying. Controlling shell thickness, however, is currently difficult to perform. Presented here is a new method in which the shell wall can be thickened by contacting the as-synthesized capsules with silicic acid. This shell thickening was observed and quantified for a moderately broad, unimodal size distribution of capsular particles, through a combination of transmission electron and confocal fluorescence microscopies. Thermogravimetric analysis confirmed the deposition of additional silica, and Coulter counter measurements showed the mean capsule diameter of ∼4.5 (2.2 μm changed negligibly with silicic acid treatment. The shell-thickening process occurred in an inward direction, in which the nanosized silicic acid oligomers most likely diffused through the permeable capsule wall and deposited within the wall and on the inner shell wall surface. Adjustable shell wall thicknesses in hybrid microcapsules provide enhanced capability for chemical encapsulation, storage, and release applications.
Journal of Nanoparticle Research, Aug 24, 2010
Gold nanoparticles (AuNP) can interact with a wide range of molecules including proteins. Whereas... more Gold nanoparticles (AuNP) can interact with a wide range of molecules including proteins. Whereas significant attention has focused on modifying the nanoparticle surface to regulate protein-AuNP assembly or influence the formation of the protein ''corona,'' modification of the protein surface as a mechanism to modulate protein-AuNP interaction has been less explored. Here, we examine this possibility utilizing three small globular proteinslysozyme with high isoelectric point (pI) and established interactions with AuNP; a-lactalbumin with similar tertiary fold to lysozyme but low pI; and myoglobin with a different globular fold and an intermediate pI. We first chemically modified these proteins to alter their charged surface functionalities, and thereby shift protein pI, and then applied multiple methods to assess protein-AuNP assembly. At pH values lower than the anticipated pI of the modified protein, AuNP exposure elicits changes in the optical absorbance of the protein-NP solutions and other properties due to aggregate formation. Above the expected pI, however, protein-AuNP interaction is minimal, and both components remain isolated, presumably because both species are negatively charged. These data demonstrate that protein modification provides a powerful tool for modulating whether nanoparticle-protein interactions result in material aggregation. The results also underscore that naturally occurring protein modifications found in vivo may be critical in defining nanoparticle-protein corona compositions. Keywords Gold nanoparticles Á Chemical modification Á Nanoparticle-protein interactions Á Aggregation Á Protein modification Á Nanobiotechnology Proteins interact with nanoparticles to generate conjugates that can either remain in suspension or assemble into complex, three-dimensional nanoarchitectures. Both forms can exhibit properties that differ from the discrete nanoparticle and protein in solution (e.g., Asuri et al. 2006; Baudhuin et al. 1989; Iosin et al.
Aiche Journal, Nov 1, 2009
There is much experimental and mathematical work that describes chemical transport from multilaye... more There is much experimental and mathematical work that describes chemical transport from multilayered films of planar geometries. There is less so, however, for chemical transport from multilayered spheres, a common structure for controlled‐release materials. Based on the Sturm–Liouville approach of Ramkrishna and Amundson (1974), explicit analytical solutions for the concentration profiles and release kinetics from spherical capsules are presented. Fluorescent dye‐release studies using single‐shelled microspheres called nanoparticle‐assembled capsules were performed to validate the model for uniformly and nonuniformly sized capsules. The combined experiment‐modeling approach allows optical microscopy images and release measurements to be readily analyzed for estimating diffusion coefficients in capsule core and shell walls. © 2009 American Institute of Chemical Engineers AIChE J, 2009
Journal of Nanoparticle Research, 2011
Gold nanoparticles (AuNP) can interact with a wide range of molecules including proteins. Whereas... more Gold nanoparticles (AuNP) can interact with a wide range of molecules including proteins. Whereas significant attention has focused on modifying the nanoparticle surface to regulate protein–AuNP assembly or influence the formation of the protein “corona,” modification of the protein surface as a mechanism to modulate protein–AuNP interaction has been less explored. Here, we examine this possibility utilizing three small globular proteins—lysozyme with high isoelectric point (pI) and established interactions with AuNP; α-lactalbumin with similar tertiary fold to lysozyme but low pI; and myoglobin with a different globular fold and an intermediate pI. We first chemically modified these proteins to alter their charged surface functionalities, and thereby shift protein pI, and then applied multiple methods to assess protein–AuNP assembly. At pH values lower than the anticipated pI of the modified protein, AuNP exposure elicits changes in the optical absorbance of the protein–NP solution...
ACS applied materials & interfaces, 2009
Colloidal particles that have nonuniform bulk or surface compositions are of emerging interest be... more Colloidal particles that have nonuniform bulk or surface compositions are of emerging interest because of their potential applications involving advanced chemical storage and delivery and the self-assembly of novel functional materials. Experimental realization of anisotropic particles is much more difficult than that for particles with uniform bulk and surface composition, however. A new wet-chemical synthesis method to anisotropic microparticles is presented. This approach makes convenient use of the unusual observation of a salt-triggered separation of two water-solubilized polyamines into colloidal aggregates with nonuniform polymer composition. The anisotropic structure of these ionically cross-linked aggregates is explained by the difference in surface tensions of the contained single-polymer domains. Contacting the polymer aggregates with silicic acid or 13-nm silica nanoparticles leads to the charge-driven formation of solid or hollow microspheres, respectively. Depending on...
Chemistry of Materials, Dec 28, 2010
Addition of silicic acid at varying levels was found to increase the shell thickness of silica na... more Addition of silicic acid at varying levels was found to increase the shell thickness of silica nanoparticle/polyamine composite microcapsules. The process of capsule wall thickening was found to take place in an inward direction by the diffusion of nanosized silicic acid ...
Journal of The American Chemical Society - J AM CHEM SOC, 2009
Topics in Catalysis, 2008
A non-surfactant-based synthesis approach to mesoporous hollow spheres through the use of colloid... more A non-surfactant-based synthesis approach to mesoporous hollow spheres through the use of colloidal silica is presented. Based on nanoparticle assembly chemistry developed previously for silica/polymer hybrid microcapsules, the room-temperature preparation follows a two-step sequence: (1) the electrostatic reaction of cationic polymer with an anionic salt solution, resulting in a suspension of salt-bridged polymer aggregates; and (2) the electrostatic reaction between this suspension and an aqueous suspension of nanoparticles (NPs). As a specific example, 13-nm silica particles, combined with polyallylamine and sodium citrate, gave silica/polymer hollow spheres with a mean diameter of 2.1 lm and a BET surface area of 4 m 2 /g. After calcination at 600°C, the resulting silica-only microcapsules had a BET surface area of 259 m 2 /g, a modal pore size of 4.0 nm, and a pore volume of 0.38 cc/g, values that exceeded those of calcined silica NPs. This colloidal silica-based material is an example of the simultaneous control of pore size (at the nanometer scale) and particle morphology (at the micrometer scale) that is possible through charge-driven NP assembly.
AIChE Journal, 2009
... Experimental and modeling analysis of diffusive release from single-shell microcapsules. Enri... more ... Experimental and modeling analysis of diffusive release from single-shell microcapsules. Enrique Muñoz Tavera 1,2 ,; Shyam B. Kadali 3 ,; Hitesh G. Bagaria 3 ,; Amy W. Liu 4 ,; Michael S. Wong 3,4,*. Article first published online: 11 AUG 2009. DOI: 10.1002/aic.11914. ...
Medical Physics
Purpose: To develop a combined targeted, drug release and hyperthermia deliverysystem for simulta... more Purpose: To develop a combined targeted, drug release and hyperthermia deliverysystem for simultaneous multimodality therapy with radiation therapy.Method and Materials: The system is based on nanoparticle‐assembled capsules (NACs) where a polymer, multivalent ion, and a nanoparticle are the only constituents required for self‐assembly formation. Poly(allylamine hydrochloride), disodium phosphate, and citrate bound magnetite nanoparticles were used to create the exterior NAC nanoshell, which encapsulates doxorubicin in the microcapsule core. An alternating magnetic field (AMF) of 20 A/m at 267 kHz was used to release the doxorubicin and heat the NAC solution. Three different nanoparticle sizes were used for these studies; 10, 30, and 50 nm to study heating rates and release profiles. Results:Magnetic nanoparticle NACs, with doxorubicin cores, were created with dimensions of ∼ 1 m capsule diameter and a ∼ 200 nm shell thickness. Heating rates of the NAC‐solution as a function of particle size were measured. Doxorubicin release profiles were measured as a function of time, nanoparticle size, and concentration. Heating rates were substantially larger for the 50 nm nanoparticles than the 10 nm particles, where temperatures in excess of 90° C over 15 minutes were measured as compared to 70° for the smaller particles. Release rate measurements show that rate is proportional to particle size. Radiation in excess of 100 Gy delivered to the NACs showed no behavioral or morphology change. Conclusion: We developed a magnetic, nanoparticle‐assembled capsule, which is a multifunctional device that can be used simultaneously for both controlled drug release and hyperthermia. The system is controlled externally through magnetic heat loss processes. These devices have many advantages; their surface can be functionalized for molecular targeting in conjunction with external magnetic field gradients and these capsules can easily be scaled up for pharmaceutical production.
Topics in Catalysis, May 30, 2008
A non-surfactant-based synthesis approach to mesoporous hollow spheres through the use of colloid... more A non-surfactant-based synthesis approach to mesoporous hollow spheres through the use of colloidal silica is presented. Based on nanoparticle assembly chemistry developed previously for silica/polymer hybrid microcapsules, the room-temperature preparation follows a two-step sequence: (1) the electrostatic reaction of cationic polymer with an anionic salt solution, resulting in a suspension of salt-bridged polymer aggregates; and (2) the electrostatic reaction between this suspension and an aqueous suspension of nanoparticles (NPs). As a specific example, 13-nm silica particles, combined with polyallylamine and sodium citrate, gave silica/polymer hollow spheres with a mean diameter of 2.1 lm and a BET surface area of 4 m 2 /g. After calcination at 600°C, the resulting silica-only microcapsules had a BET surface area of 259 m 2 /g, a modal pore size of 4.0 nm, and a pore volume of 0.38 cc/g, values that exceeded those of calcined silica NPs. This colloidal silica-based material is an example of the simultaneous control of pore size (at the nanometer scale) and particle morphology (at the micrometer scale) that is possible through charge-driven NP assembly.
ACS Applied Materials & Interfaces, Feb 20, 2009
Chemistry of Materials, Dec 29, 2010
Organic/inorganic composite microcapsules can be produced in water through a two-step chargedrive... more Organic/inorganic composite microcapsules can be produced in water through a two-step chargedriven assembly of polyallylamine, citrate anions, and 13 nm silica nanoparticles. The shell is composed of nanoparticles intermixed with polymer, and is thick enough (100s of nm) to provide structural stability before or after drying. Controlling shell thickness, however, is currently difficult to perform. Presented here is a new method in which the shell wall can be thickened by contacting the as-synthesized capsules with silicic acid. This shell thickening was observed and quantified for a moderately broad, unimodal size distribution of capsular particles, through a combination of transmission electron and confocal fluorescence microscopies. Thermogravimetric analysis confirmed the deposition of additional silica, and Coulter counter measurements showed the mean capsule diameter of ∼4.5 (2.2 μm changed negligibly with silicic acid treatment. The shell-thickening process occurred in an inward direction, in which the nanosized silicic acid oligomers most likely diffused through the permeable capsule wall and deposited within the wall and on the inner shell wall surface. Adjustable shell wall thicknesses in hybrid microcapsules provide enhanced capability for chemical encapsulation, storage, and release applications.
Journal of Nanoparticle Research, Aug 24, 2010
Gold nanoparticles (AuNP) can interact with a wide range of molecules including proteins. Whereas... more Gold nanoparticles (AuNP) can interact with a wide range of molecules including proteins. Whereas significant attention has focused on modifying the nanoparticle surface to regulate protein-AuNP assembly or influence the formation of the protein ''corona,'' modification of the protein surface as a mechanism to modulate protein-AuNP interaction has been less explored. Here, we examine this possibility utilizing three small globular proteinslysozyme with high isoelectric point (pI) and established interactions with AuNP; a-lactalbumin with similar tertiary fold to lysozyme but low pI; and myoglobin with a different globular fold and an intermediate pI. We first chemically modified these proteins to alter their charged surface functionalities, and thereby shift protein pI, and then applied multiple methods to assess protein-AuNP assembly. At pH values lower than the anticipated pI of the modified protein, AuNP exposure elicits changes in the optical absorbance of the protein-NP solutions and other properties due to aggregate formation. Above the expected pI, however, protein-AuNP interaction is minimal, and both components remain isolated, presumably because both species are negatively charged. These data demonstrate that protein modification provides a powerful tool for modulating whether nanoparticle-protein interactions result in material aggregation. The results also underscore that naturally occurring protein modifications found in vivo may be critical in defining nanoparticle-protein corona compositions. Keywords Gold nanoparticles Á Chemical modification Á Nanoparticle-protein interactions Á Aggregation Á Protein modification Á Nanobiotechnology Proteins interact with nanoparticles to generate conjugates that can either remain in suspension or assemble into complex, three-dimensional nanoarchitectures. Both forms can exhibit properties that differ from the discrete nanoparticle and protein in solution (e.g., Asuri et al. 2006; Baudhuin et al. 1989; Iosin et al.
Aiche Journal, Nov 1, 2009
There is much experimental and mathematical work that describes chemical transport from multilaye... more There is much experimental and mathematical work that describes chemical transport from multilayered films of planar geometries. There is less so, however, for chemical transport from multilayered spheres, a common structure for controlled‐release materials. Based on the Sturm–Liouville approach of Ramkrishna and Amundson (1974), explicit analytical solutions for the concentration profiles and release kinetics from spherical capsules are presented. Fluorescent dye‐release studies using single‐shelled microspheres called nanoparticle‐assembled capsules were performed to validate the model for uniformly and nonuniformly sized capsules. The combined experiment‐modeling approach allows optical microscopy images and release measurements to be readily analyzed for estimating diffusion coefficients in capsule core and shell walls. © 2009 American Institute of Chemical Engineers AIChE J, 2009
Journal of Nanoparticle Research, 2011
Gold nanoparticles (AuNP) can interact with a wide range of molecules including proteins. Whereas... more Gold nanoparticles (AuNP) can interact with a wide range of molecules including proteins. Whereas significant attention has focused on modifying the nanoparticle surface to regulate protein–AuNP assembly or influence the formation of the protein “corona,” modification of the protein surface as a mechanism to modulate protein–AuNP interaction has been less explored. Here, we examine this possibility utilizing three small globular proteins—lysozyme with high isoelectric point (pI) and established interactions with AuNP; α-lactalbumin with similar tertiary fold to lysozyme but low pI; and myoglobin with a different globular fold and an intermediate pI. We first chemically modified these proteins to alter their charged surface functionalities, and thereby shift protein pI, and then applied multiple methods to assess protein–AuNP assembly. At pH values lower than the anticipated pI of the modified protein, AuNP exposure elicits changes in the optical absorbance of the protein–NP solution...
ACS applied materials & interfaces, 2009
Colloidal particles that have nonuniform bulk or surface compositions are of emerging interest be... more Colloidal particles that have nonuniform bulk or surface compositions are of emerging interest because of their potential applications involving advanced chemical storage and delivery and the self-assembly of novel functional materials. Experimental realization of anisotropic particles is much more difficult than that for particles with uniform bulk and surface composition, however. A new wet-chemical synthesis method to anisotropic microparticles is presented. This approach makes convenient use of the unusual observation of a salt-triggered separation of two water-solubilized polyamines into colloidal aggregates with nonuniform polymer composition. The anisotropic structure of these ionically cross-linked aggregates is explained by the difference in surface tensions of the contained single-polymer domains. Contacting the polymer aggregates with silicic acid or 13-nm silica nanoparticles leads to the charge-driven formation of solid or hollow microspheres, respectively. Depending on...
Chemistry of Materials, Dec 28, 2010
Addition of silicic acid at varying levels was found to increase the shell thickness of silica na... more Addition of silicic acid at varying levels was found to increase the shell thickness of silica nanoparticle/polyamine composite microcapsules. The process of capsule wall thickening was found to take place in an inward direction by the diffusion of nanosized silicic acid ...
Journal of The American Chemical Society - J AM CHEM SOC, 2009
Topics in Catalysis, 2008
A non-surfactant-based synthesis approach to mesoporous hollow spheres through the use of colloid... more A non-surfactant-based synthesis approach to mesoporous hollow spheres through the use of colloidal silica is presented. Based on nanoparticle assembly chemistry developed previously for silica/polymer hybrid microcapsules, the room-temperature preparation follows a two-step sequence: (1) the electrostatic reaction of cationic polymer with an anionic salt solution, resulting in a suspension of salt-bridged polymer aggregates; and (2) the electrostatic reaction between this suspension and an aqueous suspension of nanoparticles (NPs). As a specific example, 13-nm silica particles, combined with polyallylamine and sodium citrate, gave silica/polymer hollow spheres with a mean diameter of 2.1 lm and a BET surface area of 4 m 2 /g. After calcination at 600°C, the resulting silica-only microcapsules had a BET surface area of 259 m 2 /g, a modal pore size of 4.0 nm, and a pore volume of 0.38 cc/g, values that exceeded those of calcined silica NPs. This colloidal silica-based material is an example of the simultaneous control of pore size (at the nanometer scale) and particle morphology (at the micrometer scale) that is possible through charge-driven NP assembly.
AIChE Journal, 2009
... Experimental and modeling analysis of diffusive release from single-shell microcapsules. Enri... more ... Experimental and modeling analysis of diffusive release from single-shell microcapsules. Enrique Muñoz Tavera 1,2 ,; Shyam B. Kadali 3 ,; Hitesh G. Bagaria 3 ,; Amy W. Liu 4 ,; Michael S. Wong 3,4,*. Article first published online: 11 AUG 2009. DOI: 10.1002/aic.11914. ...
Medical Physics
Purpose: To develop a combined targeted, drug release and hyperthermia deliverysystem for simulta... more Purpose: To develop a combined targeted, drug release and hyperthermia deliverysystem for simultaneous multimodality therapy with radiation therapy.Method and Materials: The system is based on nanoparticle‐assembled capsules (NACs) where a polymer, multivalent ion, and a nanoparticle are the only constituents required for self‐assembly formation. Poly(allylamine hydrochloride), disodium phosphate, and citrate bound magnetite nanoparticles were used to create the exterior NAC nanoshell, which encapsulates doxorubicin in the microcapsule core. An alternating magnetic field (AMF) of 20 A/m at 267 kHz was used to release the doxorubicin and heat the NAC solution. Three different nanoparticle sizes were used for these studies; 10, 30, and 50 nm to study heating rates and release profiles. Results:Magnetic nanoparticle NACs, with doxorubicin cores, were created with dimensions of ∼ 1 m capsule diameter and a ∼ 200 nm shell thickness. Heating rates of the NAC‐solution as a function of particle size were measured. Doxorubicin release profiles were measured as a function of time, nanoparticle size, and concentration. Heating rates were substantially larger for the 50 nm nanoparticles than the 10 nm particles, where temperatures in excess of 90° C over 15 minutes were measured as compared to 70° for the smaller particles. Release rate measurements show that rate is proportional to particle size. Radiation in excess of 100 Gy delivered to the NACs showed no behavioral or morphology change. Conclusion: We developed a magnetic, nanoparticle‐assembled capsule, which is a multifunctional device that can be used simultaneously for both controlled drug release and hyperthermia. The system is controlled externally through magnetic heat loss processes. These devices have many advantages; their surface can be functionalized for molecular targeting in conjunction with external magnetic field gradients and these capsules can easily be scaled up for pharmaceutical production.