Nanoreactors, in which the reactions are remotely controlled by magnetic fields, are potentially valuable in bioorthogonal chemistry for future applications. Here, we develop a silica-confined magnetothermia-induced nanoreactor (MAG-NER) by selectively growing Pd nanocrystals on a preinstalled ironoxide core inside a hollow silica nanoshell. The growth is achieved by magnetic induction. The interfacial catalytic site is activated by stimulating localized magnetothermia, and nanocompartmentalization is realized by the size-selective porous silica. Therefore, MAG-NER can be conveniently used in complex biomedia and can even be internalized to living cells, realizing an on-demand, high-performance intramolecular carbocyclization reaction by remote operation without compromising the cell viability. This work opens avenues for the design of advanced nanoreactors that complement and augment the existing bioorthogonal chemical tools.
Here, we describe and conceptualize the influence of surface engineering for hollow manganese oxide nanoparticles (HMONs)-based contrast agents for magnetic resonance imaging (MRI). A systematic study has been conducted for enhancing the relaxivities of HMONs by functionalizing their surface with various capping ligands having different anchoring groups (carboxylate, alcohol, thiol, and amine). Among all studied ligands, carboxylate-anchored ligands exhibit significant increase in magnetization value upon surface capping of HMON. Contrary to the previous hypotheses based on the surface-Mn2+ ions accessibility to water molecules, we proposed surface capping induced magnetization in HMON is responsible for the enhanced relaxivity (r 1) value. Further, in vivo imaging efficacy of oleate-capped HMON (OA-HMON) has been demonstrated in mouse brain. This study provides an insightful understanding of contrast enhancement and modulation by surface ligands on manganese oxide-based T1-contrast agents.
Nanodevices, harvesting the power of synthetic catalysts and enzymes to perform enantioselective synthesis inside cell, have never been reported. Here, we synthesized round bottom jar-like silica nanostructures (SiJARs) with a chemo-responsive metal-silicate lid. This was isolated as an intermediate structure during highly controlled solid-state nanocrystal-conversion at the arc-section of silica shell. Different catalytic noble metals (Pt, Pd, Ru) were selectively modified on the lid-section through galvanic reactions. And, lid aperture-opening was regulated by mild acidic conditions or intracellular environment which accommodated the metal nanocrystals and enzymes, and in turn created an openmouth nanoreactor. Distinct from the free enzymes, SiJARs performed asymmetric aldol reactions with high activity and enantioselectivity (yield > 99 %, ee = 95 %) and also functioned as the artificial catalytic organelles inside living cells. This work bridges the enormous potential of sophisticated nanocrystal-conversion chemistry and advanced platforms for new-to-nature catalysis.Evolutionary compartmentalization is the key structural feature of various organelles and cells to accommodate specific enzymes and cofactors, which effortlessly drive lifesustaining multistep biochemical cascades. [1] artificial organelle-like nanoreactors harnessing high activity of synthetic catalysts along with inherent handedness of enzymes, can result diversified platforms for bioorthogonal synthesis. [2, 3] These chemo-enzymatic systems can asymmetrically synthesize chiral enantiomeric bioactive molecules, [4] possessing distinct pharmacological and toxicological systemic responses and in turn leading to advanced bioimaging, therapeutic and biotechnological applications. [5] Variety of nature-inspired hollow nanostructures, which consist of silica/silicate [4b,c, 6] and polymers/micelles [3a, 7] confining catalytic nanocrystals (NCs), enzymes or both, have demonstrated improved catalysis that are mostly limited to abiotic conditions. [8] Microemulsion-, sacrificial template-, and one-pot entrapment-based methods for pre-encapsulation of bio/nano-catalysts inside a confining nano-housing, often involve difficult to control multiple synthetic steps, harsh conditions, biphasic non-aqueous solvents and complex reagents. [9] Major challenge to design nanoreactors for intracellular application is to reliably colocalize and maintain the reactive surfaces of catalytic NCs along with the protection of enzymes from de-activation. [4,10] In this regard, silica nanostructures are highly appealing for wide range of catalytic and biomedical applications owing to their chemical inertness, high stability, biocompatibility and synthetic flexibility. [11] Previously, we developed solid-state conversion strategy for reversible hollowing of silica-coated manganese oxide (MnO@SiO 2 ) [12] and the post-synthetic modification of the hollow silica interiors with catalytic noble metals. [13] However, these microporous closed shells restrict the entry and co-...
Nanodevices, harvesting the power of synthetic catalysts and enzymes to perform enantioselective synthesis inside cell, have never been reported. Here, we synthesized round bottom jar-like silica nanostructures (SiJARs) with a chemo-responsive metal-silicate lid. This was isolated as an intermediate structure during highly controlled solid-state nanocrystal-conversion at the arc-section of silica shell. Different catalytic noble metals (Pt, Pd, Ru) were selectively modified on the lid-section through galvanic reactions. And, lid aperture-opening was regulated by mild acidic conditions or intracellular environment which accommodated the metal nanocrystals and enzymes, and in turn created an openmouth nanoreactor. Distinct from the free enzymes, SiJARs performed asymmetric aldol reactions with high activity and enantioselectivity (yield > 99 %, ee = 95 %) and also functioned as the artificial catalytic organelles inside living cells. This work bridges the enormous potential of sophisticated nanocrystal-conversion chemistry and advanced platforms for new-to-nature catalysis.Evolutionary compartmentalization is the key structural feature of various organelles and cells to accommodate specific enzymes and cofactors, which effortlessly drive lifesustaining multistep biochemical cascades. [1] artificial organelle-like nanoreactors harnessing high activity of synthetic catalysts along with inherent handedness of enzymes, can result diversified platforms for bioorthogonal synthesis. [2, 3] These chemo-enzymatic systems can asymmetrically synthesize chiral enantiomeric bioactive molecules, [4] possessing distinct pharmacological and toxicological systemic responses and in turn leading to advanced bioimaging, therapeutic and biotechnological applications. [5] Variety of nature-inspired hollow nanostructures, which consist of silica/silicate [4b,c, 6] and polymers/micelles [3a, 7] confining catalytic nanocrystals (NCs), enzymes or both, have demonstrated improved catalysis that are mostly limited to abiotic conditions. [8] Microemulsion-, sacrificial template-, and one-pot entrapment-based methods for pre-encapsulation of bio/nano-catalysts inside a confining nano-housing, often involve difficult to control multiple synthetic steps, harsh conditions, biphasic non-aqueous solvents and complex reagents. [9] Major challenge to design nanoreactors for intracellular application is to reliably colocalize and maintain the reactive surfaces of catalytic NCs along with the protection of enzymes from de-activation. [4,10] In this regard, silica nanostructures are highly appealing for wide range of catalytic and biomedical applications owing to their chemical inertness, high stability, biocompatibility and synthetic flexibility. [11] Previously, we developed solid-state conversion strategy for reversible hollowing of silica-coated manganese oxide (MnO@SiO 2 ) [12] and the post-synthetic modification of the hollow silica interiors with catalytic noble metals. [13] However, these microporous closed shells restrict the entry and co-...
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