Youssry Botros - Academia.edu (original) (raw)
Papers by Youssry Botros
Accounts of Chemical Research, Mar 17, 2020
ConspectusCyclodextrin-based metal-organic frameworks (CD-MOFs), derived from γ-cyclodextrin (γ-C... more ConspectusCyclodextrin-based metal-organic frameworks (CD-MOFs), derived from γ-cyclodextrin (γ-CD) and potassium ions, constitute a new class of porous, renewable, and edible MOFs that can be synthesized wholly from naturally occurring starting materials on a large scale. γ-CD is a C8 symmetrical cyclic oligosaccharide, composed of eight asymmetric α-1,4-linked d-glucopyranosyl residues, which possesses a bucket-shaped cavity with an inner diameter of ∼1 nm and a depth of ∼0.8 nm. Upon combining 1 equiv of γ-CD with 8 equiv of potassium hydroxide in aqueous solution, followed by vapor-diffusion of MeOH (or EtOH) into the solution during several days, CD-MOF-1 is obtained as cubic crystals. It was discovered serendipitously in 2010 as the first CD-MOF with a cubic cell of space group I432 and unit cell dimensions of approximately 31 × 31 × 31 Å3. Other CD-MOFs, namely, CD-MOF-2 and CD-MOF-3, can be obtained, respectively, wherein potassium is replaced with rubidium and cesium ions. CD-MOFs comprise infinite body-centered frameworks of (γ-CD)6 cubic units linked by alkali metal cations with spherical pores which reside at the center of the cubes interconnected by both cylindrical and triangular channels.During the past decade, CD-MOFs have emerged as a new class of multifunctional materials based on a porous framework with an extended structure displaying robust crystallinity, permanent porosity, and biocompatibility. The family of CD-MOFs has been enlarged by a growing collection of metal nodes involving alkali metal cations (Li+, Na+, K+, Rb+, Cs+) and γ-CD as well as its derivatives. As a result of the ability of their porous extended frameworks to absorb guest molecules, including gases, drug molecules, metal-based nanoclusters, and nanoparticles, CD-MOFs have potential applications in areas as disparate as adsorption and separation, sensing, template syntheses of metal-based nanoparticles and gels, electrical memory, drug delivery, and catalyst stabilization.In this Account, we tell the story of CD-MOFs, a scientific discovery that was made in our research laboratory at the Northwestern University, and the subsequent commercialization of CD-MOF technology on the part of a spinoff company, which developed a line of successful skin care products. This Account includes representative synthetic methods for the preparation of CD-MOFs, along with a brief overview of their structural features and a general summary of their state-of-the-art applications. The examples, however, are only illustrative, and a significant body of additional findings is emanating from our own laboratory and others, especially in the development of new synthetic strategies, tuning the framework stabilities, and exploring the guest-inclusion properties of CD-MOFs. We refer readers to communications, papers, and reviews on CD-MOFs and to references therein. We also put on record how CD-MOFs have been rebranded as organic molecular vessels (OMVs), a smart, functional, environmentally friendly delivery platform for commercial skin care applications. We hope that, in the telling and retelling of the story of CD-MOFs, this Account may encourage the commercialization of discoveries that have been made in other research laboratories.
Journal of Nanomedicine & Nanotechnology, Aug 19, 2016
This paper addresses data collection mechanisms for factory automation systems. The two-fold purp... more This paper addresses data collection mechanisms for factory automation systems. The two-fold purpose of this paper includes describing some of the key benefits of the Equipment Data Acquisition (EDA) interface being defined by SEMI and addressing challenges associated with migration to this interface. Before reviewing and addressing the contents of the emerging EDA standard we will detail problems, issues and
IEEE Microwave and Guided Wave Letters, 1999
The anisotropic and active properties of the perfectly matched layer (PML) absorbers significantl... more The anisotropic and active properties of the perfectly matched layer (PML) absorbers significantly deteriorate the finite-element method (FEM) system condition and as a result, convergence of the iterative solver is substantially affected. To address this issue, we examine the generalized minimal residual (GMRES) solver for solving finite-element systems terminated with PML. A strong approximate inverse preconditioner (AIPC) is coupled with a GMRES solver to speed up convergence and consequently reduce the overall CPU time.
Because of their superior absorption characteristics, the Perfectly Matched Layer (PML) absorbers... more Because of their superior absorption characteristics, the Perfectly Matched Layer (PML) absorbers are used in truncating finite element domains. However, their implementation is equivalent to imposing active elements inside the main mesh. Consequently, the condition number of the resulting systems deteriorates. In this work, an efficient preconditioned generalized minimal residual (GMRES) iterative solver is developed and applied to systems truncated
Journal of Nanomedicine & Nanotechnology, Dec 2, 2016
Wiley Encyclopedia of Electrical and Electronics Engineering, 1999
An entry from the Cambridge Structural Database, the world's repository for small molecule cr... more An entry from the Cambridge Structural Database, the world's repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
Organic Letters, Jul 7, 2010
An approach to the design and fabrication of mechanized mesoporous silica nanoparticles is demons... more An approach to the design and fabrication of mechanized mesoporous silica nanoparticles is demonstrated at the proof of principle level. It relies on the reductive cleavage of disulfide bonds within an integrated nanosystem, wherein surface-bound rotaxanes incorporate disulfide bonds in their stalks, which are encircled by cucurbit[6]uril or alpha-cyclodextrin rings, until reductive chemistry is performed, resulting in the snapping of the stalks of the rotaxanes, leading to cargo release from the inside of the nanoparticles.
An entry from the Cambridge Structural Database, the world's repository for small molecule cr... more An entry from the Cambridge Structural Database, the world's repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
Journal of the American Chemical Society, Apr 20, 2011
Alkanediamines serve as neutral guests for the recently discovered host pillar[5]arene. The propo... more Alkanediamines serve as neutral guests for the recently discovered host pillar[5]arene. The proposed [2]pseudorotaxane nature of the superstructure of the 1:1 host-guest complexes is supported by the template-directed synthesis of a related [2]rotaxane. A synthetic route to monofunctional pillar[5]arenes has also been developed, allowing for the creation of a fluorescent sensor for alkylamine binding. The precursors to this host could act as starting points for a large library of monofunctional pillar[5]arene macrocycles.
Chemical Communications, 2010
Tetrahydrofuran (THF) was distilled over sodium benzophenone ketyl radical under an atmosphere of... more Tetrahydrofuran (THF) was distilled over sodium benzophenone ketyl radical under an atmosphere of N 2. Anhydrous dichloromethane and acetonitrile were obtained from an EMD Chemicals DrySolv® system. Anhydrous p-dioxane was purchased from Aldrich and handled under an atmosphere of argon. CDCl 3 , C 6 D 6 , CD 2 Cl 2 and (CD 3) 2 CO were purchased from Aldrich and used without further purification. All other reagents were purchased from commercial sources and were used without further purification, unless indicated otherwise. All reactions were carried out under an atmosphere of N 2 in flamedried flasks using freshly distilled or anhydrous solvents, unless indicated otherwise. Thin-layer chromatography (TLC) was carried out using glass plates, precoated with silica gel 60 with fluorescent indicator (Whatman LK6F). The plates were inspected by UV light (254 nm) and/or potassium permanganate stain. Column chromatography purifications were carried out using the flash technique using silica gel 60F (230-400 mesh). 1 H and 13 C NMR spectra were recorded on a Bruker ARX500 (500 MHz) spectrometer. The chemical shifts (δ) for 1 H spectra are given in ppm are referenced to the residual proton signal of the deuterated solvent. The chemical shifts (δ) for 13 C spectra are referenced relative to the signal from the carbon of the deuterated solvent. High-resolution mass spectra were measured on a Finnigan LCQ iontrap mass spectrometer (HR-ESI). The general experimental details for the preparation and analysis of (SS)-MOF-1020 and (RR)-MOF-1020 can be found on page S16. Synthetic Procedures The synthesis and characterization of all intermediates en route to (SS)-2 are provided. The synthesis of (RR)-2 was performed in a similar fashion.
![Research paper thumbnail of Pillar[5]arene as a Co-Factor in Templating Rotaxane Formation](https://attachments.academia-assets.com/113247545/thumbnails/1.jpg)
](Journal of the American Chemical Society, Oct 30, 2013
rate, often ca. 10 5-fold compared to the uncatalyzed reaction. Since its discovery by Mock, the ... more rate, often ca. 10 5-fold compared to the uncatalyzed reaction. Since its discovery by Mock, the CB-catalyzed 1,3-dipolar cycloaddition (CB-AAC) has found application in the construction of polymers, 14 mechanically interlocked molecules (MIMs) 15 and pH responsive controlled-release systems. Despite the fact that both the CB-AAC and the Cu(I)-catalyzed cycloaddition (CuAAC) exhibit favorable kinetics and regiospecificities, the former has found comparatively few applications compared to the now ubiquitous CuAAC. Perhaps the fact that CB is not as freely available as copper salts and is less convenient to handle because of its poor solubility 17 in water 18 and other common laboratory solvents, 19 add up to explanations of a sort. The greatest drawback of the CB-AAC, however, is its substrate scope − to date, all reports are restricted to describing reactions between propargylammonium and azidoethyl-ammonium derivatives. This limited scope can be rationalized by considering the cyclization mechanism and noncovalent bonding interactions which underpin the reaction. CB-AAC proceeds by means of the initial formation of a hetero-ternary complex, which renders the cyclization a pseudo-unimolecular process as a result of bringing the triple bond in the propargylammonium ion and the azide function in the azidoethylammonium ion into close proximity as well as aligning them so that they are poised to undergo trizaole ring formation. 11a, 20 The entropic cost of bringing the CB and AAC precursors together is compensated 21 for by the favorable binding enthalpy and the release of high energy water molecules from the cavity of the CB. Charge-dipole and hydrogen bonding interactions between the secondary dialkylammonium ions and the carbonyl groups around the rim of the CB are maximized when the NH 2 + centers are close to the planes of carbonyl oxygens, a requirement which dictates the geometry of the ternary complex. Consequently, altering the
Angewandte Chemie, Jun 29, 2011
ABSTRACT A redox-controllable bistable [2]rotaxane has been synthesized using templation and clic... more ABSTRACT A redox-controllable bistable [2]rotaxane has been synthesized using templation and click chemistry. With assistance from a sacrificial electron donor, light-triggered switching through numerous cycles can be initiated by radical-pairing interactions between the reduced forms of the cyclophane and the bipyridinium unit in aqueous solution in the absence of air. In the presence of air (O2), the interactions are reset by donor-acceptor charge transfer.
Angewandte Chemie, Apr 13, 2012
Combination drug therapy, [1] a regimen in which multiple drugs with different therapeutic outcom... more Combination drug therapy, [1] a regimen in which multiple drugs with different therapeutic outcomes are used in parallel or in sequence, has become one of the dominant strategies in the clinical treatment of HIV/AIDS, [2] diabetes, [3] and cancer. [4] In cancer therapy, for example, the U.S. Food and Drug Administration (FDA) approved the use in 2006 of Avastin in combination with Carboplatin and Paclitaxel for the initial systemic treatment of patients with lung cancer. Unlike monotherapy, combination therapy maximizes ther
Journal of the American Chemical Society, Aug 27, 2010
The development of drug delivery systems for the targeted and on-demand release of pharmaceutical... more The development of drug delivery systems for the targeted and on-demand release of pharmaceutical products has risen rapidly to become a contemporary challenge in the field of nanobiotechnology. Biocompatible mechanized phosphonate-clothed silica nanoparticles have been designed and fabricated in which the supramolecular machinery, which covers the surfaces of the nanoparticles, behaves like nanopistons, releasing encapsulated guest molecules in a controlled fashion under acidic conditions. The mechanized nanoparticles consist of a monolayer of-cyclodextrin (-CD) rings positioned selectively around the orifices of the nanopores of the mesoporous nanoparticles. A rhodamine B/benzidine conjugate was prepared for use as the nanopistons for movement in and out of the cylindrical cavities provided by the-CD rings on the surfaces of the nanoparticles. Luminescence experiments indicated that the mechanized nanoparticles were able to store small cargo molecules (e.g., 2,6-naphthalenedisulfonic acid disodium) within their nanopores at neutral pH and then release them by passage through the cavities of the-CD rings as soon as the pH was lowered to ∼5. In further investigations, the phosphonate-covered silica nanoparticles were functionalized selectively with the-CD rings, but on this occasion, the seven linkers attaching the rings to the orifices surrounding the nanopores contained cleavable imine double bonds. The-CD rings on the surface of the nanoparticles served as gates for the storage of large cargo molecules (e.g., rhodamine B) inside the nanopores of the nanoparticles under neutral conditions. Since imine bonds can be hydrolyzed under acidic conditions, the-CD rings could be severed from the surface of the nanoparticles when the pH was decreased to 6, releasing the large cargo molecules. The results described here present a significant step toward the development of pH-responsive nanoparticle-based dual drug delivery vehicles that are potentially capable of being interfaced with biological systems.
Nanoscale, Jan 30, 2015
Gating of mesoporous silica nanoparticles (MSNs) with the stimuli-responsive poly(β-amino ester) ... more Gating of mesoporous silica nanoparticles (MSNs) with the stimuli-responsive poly(β-amino ester) has been achieved. This hybrid nanocarrier releases doxorubicin (DOX) under acidic conditions or in the presence of porcine liver esterase. The DOX loaded poly(β-amino ester)-capped MSNs reduce cell viability when tested on MDA-MB-231 human breast cancer cells.
Accounts of Chemical Research, Mar 17, 2020
ConspectusCyclodextrin-based metal-organic frameworks (CD-MOFs), derived from γ-cyclodextrin (γ-C... more ConspectusCyclodextrin-based metal-organic frameworks (CD-MOFs), derived from γ-cyclodextrin (γ-CD) and potassium ions, constitute a new class of porous, renewable, and edible MOFs that can be synthesized wholly from naturally occurring starting materials on a large scale. γ-CD is a C8 symmetrical cyclic oligosaccharide, composed of eight asymmetric α-1,4-linked d-glucopyranosyl residues, which possesses a bucket-shaped cavity with an inner diameter of ∼1 nm and a depth of ∼0.8 nm. Upon combining 1 equiv of γ-CD with 8 equiv of potassium hydroxide in aqueous solution, followed by vapor-diffusion of MeOH (or EtOH) into the solution during several days, CD-MOF-1 is obtained as cubic crystals. It was discovered serendipitously in 2010 as the first CD-MOF with a cubic cell of space group I432 and unit cell dimensions of approximately 31 × 31 × 31 Å3. Other CD-MOFs, namely, CD-MOF-2 and CD-MOF-3, can be obtained, respectively, wherein potassium is replaced with rubidium and cesium ions. CD-MOFs comprise infinite body-centered frameworks of (γ-CD)6 cubic units linked by alkali metal cations with spherical pores which reside at the center of the cubes interconnected by both cylindrical and triangular channels.During the past decade, CD-MOFs have emerged as a new class of multifunctional materials based on a porous framework with an extended structure displaying robust crystallinity, permanent porosity, and biocompatibility. The family of CD-MOFs has been enlarged by a growing collection of metal nodes involving alkali metal cations (Li+, Na+, K+, Rb+, Cs+) and γ-CD as well as its derivatives. As a result of the ability of their porous extended frameworks to absorb guest molecules, including gases, drug molecules, metal-based nanoclusters, and nanoparticles, CD-MOFs have potential applications in areas as disparate as adsorption and separation, sensing, template syntheses of metal-based nanoparticles and gels, electrical memory, drug delivery, and catalyst stabilization.In this Account, we tell the story of CD-MOFs, a scientific discovery that was made in our research laboratory at the Northwestern University, and the subsequent commercialization of CD-MOF technology on the part of a spinoff company, which developed a line of successful skin care products. This Account includes representative synthetic methods for the preparation of CD-MOFs, along with a brief overview of their structural features and a general summary of their state-of-the-art applications. The examples, however, are only illustrative, and a significant body of additional findings is emanating from our own laboratory and others, especially in the development of new synthetic strategies, tuning the framework stabilities, and exploring the guest-inclusion properties of CD-MOFs. We refer readers to communications, papers, and reviews on CD-MOFs and to references therein. We also put on record how CD-MOFs have been rebranded as organic molecular vessels (OMVs), a smart, functional, environmentally friendly delivery platform for commercial skin care applications. We hope that, in the telling and retelling of the story of CD-MOFs, this Account may encourage the commercialization of discoveries that have been made in other research laboratories.
Journal of Nanomedicine & Nanotechnology, Aug 19, 2016
This paper addresses data collection mechanisms for factory automation systems. The two-fold purp... more This paper addresses data collection mechanisms for factory automation systems. The two-fold purpose of this paper includes describing some of the key benefits of the Equipment Data Acquisition (EDA) interface being defined by SEMI and addressing challenges associated with migration to this interface. Before reviewing and addressing the contents of the emerging EDA standard we will detail problems, issues and
IEEE Microwave and Guided Wave Letters, 1999
The anisotropic and active properties of the perfectly matched layer (PML) absorbers significantl... more The anisotropic and active properties of the perfectly matched layer (PML) absorbers significantly deteriorate the finite-element method (FEM) system condition and as a result, convergence of the iterative solver is substantially affected. To address this issue, we examine the generalized minimal residual (GMRES) solver for solving finite-element systems terminated with PML. A strong approximate inverse preconditioner (AIPC) is coupled with a GMRES solver to speed up convergence and consequently reduce the overall CPU time.
Because of their superior absorption characteristics, the Perfectly Matched Layer (PML) absorbers... more Because of their superior absorption characteristics, the Perfectly Matched Layer (PML) absorbers are used in truncating finite element domains. However, their implementation is equivalent to imposing active elements inside the main mesh. Consequently, the condition number of the resulting systems deteriorates. In this work, an efficient preconditioned generalized minimal residual (GMRES) iterative solver is developed and applied to systems truncated
Journal of Nanomedicine & Nanotechnology, Dec 2, 2016
Wiley Encyclopedia of Electrical and Electronics Engineering, 1999
An entry from the Cambridge Structural Database, the world's repository for small molecule cr... more An entry from the Cambridge Structural Database, the world's repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
Organic Letters, Jul 7, 2010
An approach to the design and fabrication of mechanized mesoporous silica nanoparticles is demons... more An approach to the design and fabrication of mechanized mesoporous silica nanoparticles is demonstrated at the proof of principle level. It relies on the reductive cleavage of disulfide bonds within an integrated nanosystem, wherein surface-bound rotaxanes incorporate disulfide bonds in their stalks, which are encircled by cucurbit[6]uril or alpha-cyclodextrin rings, until reductive chemistry is performed, resulting in the snapping of the stalks of the rotaxanes, leading to cargo release from the inside of the nanoparticles.
An entry from the Cambridge Structural Database, the world's repository for small molecule cr... more An entry from the Cambridge Structural Database, the world's repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
Journal of the American Chemical Society, Apr 20, 2011
Alkanediamines serve as neutral guests for the recently discovered host pillar[5]arene. The propo... more Alkanediamines serve as neutral guests for the recently discovered host pillar[5]arene. The proposed [2]pseudorotaxane nature of the superstructure of the 1:1 host-guest complexes is supported by the template-directed synthesis of a related [2]rotaxane. A synthetic route to monofunctional pillar[5]arenes has also been developed, allowing for the creation of a fluorescent sensor for alkylamine binding. The precursors to this host could act as starting points for a large library of monofunctional pillar[5]arene macrocycles.
Chemical Communications, 2010
Tetrahydrofuran (THF) was distilled over sodium benzophenone ketyl radical under an atmosphere of... more Tetrahydrofuran (THF) was distilled over sodium benzophenone ketyl radical under an atmosphere of N 2. Anhydrous dichloromethane and acetonitrile were obtained from an EMD Chemicals DrySolv® system. Anhydrous p-dioxane was purchased from Aldrich and handled under an atmosphere of argon. CDCl 3 , C 6 D 6 , CD 2 Cl 2 and (CD 3) 2 CO were purchased from Aldrich and used without further purification. All other reagents were purchased from commercial sources and were used without further purification, unless indicated otherwise. All reactions were carried out under an atmosphere of N 2 in flamedried flasks using freshly distilled or anhydrous solvents, unless indicated otherwise. Thin-layer chromatography (TLC) was carried out using glass plates, precoated with silica gel 60 with fluorescent indicator (Whatman LK6F). The plates were inspected by UV light (254 nm) and/or potassium permanganate stain. Column chromatography purifications were carried out using the flash technique using silica gel 60F (230-400 mesh). 1 H and 13 C NMR spectra were recorded on a Bruker ARX500 (500 MHz) spectrometer. The chemical shifts (δ) for 1 H spectra are given in ppm are referenced to the residual proton signal of the deuterated solvent. The chemical shifts (δ) for 13 C spectra are referenced relative to the signal from the carbon of the deuterated solvent. High-resolution mass spectra were measured on a Finnigan LCQ iontrap mass spectrometer (HR-ESI). The general experimental details for the preparation and analysis of (SS)-MOF-1020 and (RR)-MOF-1020 can be found on page S16. Synthetic Procedures The synthesis and characterization of all intermediates en route to (SS)-2 are provided. The synthesis of (RR)-2 was performed in a similar fashion.
Journal of the American Chemical Society, Oct 30, 2013
rate, often ca. 10 5-fold compared to the uncatalyzed reaction. Since its discovery by Mock, the ... more rate, often ca. 10 5-fold compared to the uncatalyzed reaction. Since its discovery by Mock, the CB-catalyzed 1,3-dipolar cycloaddition (CB-AAC) has found application in the construction of polymers, 14 mechanically interlocked molecules (MIMs) 15 and pH responsive controlled-release systems. Despite the fact that both the CB-AAC and the Cu(I)-catalyzed cycloaddition (CuAAC) exhibit favorable kinetics and regiospecificities, the former has found comparatively few applications compared to the now ubiquitous CuAAC. Perhaps the fact that CB is not as freely available as copper salts and is less convenient to handle because of its poor solubility 17 in water 18 and other common laboratory solvents, 19 add up to explanations of a sort. The greatest drawback of the CB-AAC, however, is its substrate scope − to date, all reports are restricted to describing reactions between propargylammonium and azidoethyl-ammonium derivatives. This limited scope can be rationalized by considering the cyclization mechanism and noncovalent bonding interactions which underpin the reaction. CB-AAC proceeds by means of the initial formation of a hetero-ternary complex, which renders the cyclization a pseudo-unimolecular process as a result of bringing the triple bond in the propargylammonium ion and the azide function in the azidoethylammonium ion into close proximity as well as aligning them so that they are poised to undergo trizaole ring formation. 11a, 20 The entropic cost of bringing the CB and AAC precursors together is compensated 21 for by the favorable binding enthalpy and the release of high energy water molecules from the cavity of the CB. Charge-dipole and hydrogen bonding interactions between the secondary dialkylammonium ions and the carbonyl groups around the rim of the CB are maximized when the NH 2 + centers are close to the planes of carbonyl oxygens, a requirement which dictates the geometry of the ternary complex. Consequently, altering the
Angewandte Chemie, Jun 29, 2011
ABSTRACT A redox-controllable bistable [2]rotaxane has been synthesized using templation and clic... more ABSTRACT A redox-controllable bistable [2]rotaxane has been synthesized using templation and click chemistry. With assistance from a sacrificial electron donor, light-triggered switching through numerous cycles can be initiated by radical-pairing interactions between the reduced forms of the cyclophane and the bipyridinium unit in aqueous solution in the absence of air. In the presence of air (O2), the interactions are reset by donor-acceptor charge transfer.
Angewandte Chemie, Apr 13, 2012
Combination drug therapy, [1] a regimen in which multiple drugs with different therapeutic outcom... more Combination drug therapy, [1] a regimen in which multiple drugs with different therapeutic outcomes are used in parallel or in sequence, has become one of the dominant strategies in the clinical treatment of HIV/AIDS, [2] diabetes, [3] and cancer. [4] In cancer therapy, for example, the U.S. Food and Drug Administration (FDA) approved the use in 2006 of Avastin in combination with Carboplatin and Paclitaxel for the initial systemic treatment of patients with lung cancer. Unlike monotherapy, combination therapy maximizes ther
Journal of the American Chemical Society, Aug 27, 2010
The development of drug delivery systems for the targeted and on-demand release of pharmaceutical... more The development of drug delivery systems for the targeted and on-demand release of pharmaceutical products has risen rapidly to become a contemporary challenge in the field of nanobiotechnology. Biocompatible mechanized phosphonate-clothed silica nanoparticles have been designed and fabricated in which the supramolecular machinery, which covers the surfaces of the nanoparticles, behaves like nanopistons, releasing encapsulated guest molecules in a controlled fashion under acidic conditions. The mechanized nanoparticles consist of a monolayer of-cyclodextrin (-CD) rings positioned selectively around the orifices of the nanopores of the mesoporous nanoparticles. A rhodamine B/benzidine conjugate was prepared for use as the nanopistons for movement in and out of the cylindrical cavities provided by the-CD rings on the surfaces of the nanoparticles. Luminescence experiments indicated that the mechanized nanoparticles were able to store small cargo molecules (e.g., 2,6-naphthalenedisulfonic acid disodium) within their nanopores at neutral pH and then release them by passage through the cavities of the-CD rings as soon as the pH was lowered to ∼5. In further investigations, the phosphonate-covered silica nanoparticles were functionalized selectively with the-CD rings, but on this occasion, the seven linkers attaching the rings to the orifices surrounding the nanopores contained cleavable imine double bonds. The-CD rings on the surface of the nanoparticles served as gates for the storage of large cargo molecules (e.g., rhodamine B) inside the nanopores of the nanoparticles under neutral conditions. Since imine bonds can be hydrolyzed under acidic conditions, the-CD rings could be severed from the surface of the nanoparticles when the pH was decreased to 6, releasing the large cargo molecules. The results described here present a significant step toward the development of pH-responsive nanoparticle-based dual drug delivery vehicles that are potentially capable of being interfaced with biological systems.
Nanoscale, Jan 30, 2015
Gating of mesoporous silica nanoparticles (MSNs) with the stimuli-responsive poly(β-amino ester) ... more Gating of mesoporous silica nanoparticles (MSNs) with the stimuli-responsive poly(β-amino ester) has been achieved. This hybrid nanocarrier releases doxorubicin (DOX) under acidic conditions or in the presence of porcine liver esterase. The DOX loaded poly(β-amino ester)-capped MSNs reduce cell viability when tested on MDA-MB-231 human breast cancer cells.