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1.
J Am Chem Soc ; 145(34): 18855-18864, 2023 Aug 30.
Artigo em Inglês | MEDLINE | ID: mdl-37587434

RESUMO

Water has been recognized as an excellent solvent for maneuvering both the catalytic activity and selectivity, especially in the case of heterogeneous catalysis. However, maintaining the active catalytic species in their higher oxidation states (IV/V) while retaining the catalytic activity and recyclability in water is an enormous challenge. Herein, we have developed a solution to this problem using covalent organic frameworks (COFs) to immobilize the (Et4N)2[FeIII(Cl)bTAML] molecules, taking advantage of the COF's morphology and surface charge. By using the visible light and [CoIII(NH3)5Cl]Cl2 as a sacrificial electron acceptor within the COF, we have successfully generated and stabilized the [(bTAML)FeIV-O-FeIV(bTAML)]- species in water. The COF backbone simultaneously acts as a porous host and a photosensitizer. This is the first time that the photochemically generated Fe2IV-µ-oxo radical cation species has demonstrated high catalytic activity with moderate to high yield for the selective oxidation of the unactivated C-H bonds, even in water. To enhance the catalytic activity and achieve good recyclability, we have developed a TpDPP COF film by transforming the TpDPP COF nanospheres. We have achieved the regio- and stereoselective functionalization of unactivated C-H bonds of alkanes and alkenes (3°:2° = 102:1 for adamantane with the COF film), which is improbable in homogeneous conditions. The film exhibits C-H bond oxidation with higher catalytic yield (32-98%) and a higher degree of selectivity (cis/trans = 74:1; 3°:2° = 100:1 for cis-decalin).

2.
Inorg Chem ; 62(49): 20439-20449, 2023 Dec 11.
Artigo em Inglês | MEDLINE | ID: mdl-38001041

RESUMO

High-valent metal-fluoride complexes are currently being explored for concerted proton-electron transfer (CPET) reactions, the driving force being the high bond dissociation energy of H-F (BDEH-F = 135 kcal/mol) that is formed after the reaction. Ni(III)-fluoride-based complexes on the pyridine dicarboxamide pincer ligand framework have been utilized for CPET reactions toward phenols and hydrocarbons. We have replaced the central pyridine ligand with an N-heterocyclic carbene carbene to probe its effect in both stabilizing the high-valent Ni(III) state and its ability to initiate CPET reactions. We report a monomeric carbene-diamide-based Ni(II)-fluoride pincer complex that was characterized through 1H/19F NMR, mass spectrometry, UV-vis, and X-ray crystallography analysis. Although carbenes and deprotonated carboxamides in the Ni(II)-fluoride complex are expected to stabilize the Ni(III) state upon oxidation, the Ni(III)/Ni(II) redox process occurred at very high potential (0.87 V vs Fc+/Fc, dichloromethane) and was irreversible. Structural studies indicate significant distortion in the imidazolium "NCN" carbene plane of Ni(II)-fluoride caused by the formation of six-membered metallacycles. The high-valent NiIII-fluoride analogue was synthesized by the addition of 1.0 equiv CTAN (ceric tetrabutylammonium nitrate) in dichloromethane at -20 °C which was characterized by UV-vis, mass spectrometry, and EPR spectroscopy. Density functional theory studies indicate that the Ni-carbene bond elongated, while the Ni-F bond shortened upon oxidation to the Ni(III) species. The high-valent Ni(III)-fluoride was found to react with the substituted phenols. Analysis of the KIE and linear free energy relationship correlates well with the CPET nature of the reaction. Preliminary analysis indicates that the CPET is asynchronous and is primarily driven by the E0' of the Ni(III)-fluoride complex.

3.
J Am Chem Soc ; 143(22): 8426-8436, 2021 06 09.
Artigo em Inglês | MEDLINE | ID: mdl-34029465

RESUMO

Heterogeneous catalysis in water has not been explored beyond certain advantages such as recyclability and recovery of the catalysts from the reaction medium. Moreover, poor yield, extremely low selectivity, and active catalytic site deactivation further underrate the heterogeneous catalysis in water. Considering these facts, we have designed and synthesized solution-dispersible porous covalent organic framework (COF) nanospheres. We have used their distinctive morphology and dispersibility to functionalize unactivated C-H bonds of alkanes heterogeneously with high catalytic yield (42-99%) and enhanced regio- and stereoselectivity (3°:2° = 105:1 for adamantane). Further, the fabrication of catalyst-immobilized COF nanofilms via covalent self-assembly of catalytic COF nanospheres for the first time has become the key toward converting the catalytically inactive homogeneous catalysts into active and effective heterogeneous catalysts operating in water. This unique covalent self-assembly occurs through the protrusion of the fibers at the interface of two nanospheres, transmuting the catalytic spheres into films without any leaching of catalyst molecules. The catalyst-immobilized porous COF nanofilms' chemical functionality and hydrophobic environment stabilize the high-valent transient active oxoiron(V) intermediate in water and restricts the active catalytic site's deactivation. These COF nanofilms functionalize the unactivated C-H bonds in water with a high catalytic yield (45-99%) and with a high degree of selectivity (cis:trans = 155:1; 3°:2° = 257:1, for cis-1,2-dimethylcyclohexane). To establish this approach's "practical implementation", we conducted the catalysis inflow (TON = 424 ± 5) using catalyst-immobilized COF nanofilms fabricated on a macroporous polymeric support.

4.
Phys Chem Chem Phys ; 20(20): 13845-13850, 2018 May 23.
Artigo em Inglês | MEDLINE | ID: mdl-29717729

RESUMO

Monomeric iron-oxo units have been confirmed as intermediates involved in the C-H bond activation in various metallo-enzymes. Biomimetic oxoiron complexes of the biuret modified tetra-amido macrocyclic ligand (bTAML) have been demonstrated to oxidize a wide variety of unactivated C-H bonds. In the current work, density functional theory (DFT) has been employed to investigate the hydrogen abstraction (HAT) reactivity differences across a series of bTAML complexes. The cause for the differences in the HAT energy barriers has been found to be the relative changes in the energy of the frontier molecular orbitals (FMOs) induced by electronic perturbation.

8.
Inorg Chem ; 56(18): 10852-10860, 2017 Sep 18.
Artigo em Inglês | MEDLINE | ID: mdl-28841016

RESUMO

Nonheme iron complexes bearing tetradentate N-atom-donor ligands with cis labile sites show great promise for chemoselective aliphatic C-H hydroxylation. However, several challenges still limit their widespread application. We report a mechanism-guided development of a peroxidase mimicking iron complex based on the bTAML macrocyclic ligand framework (Fe-bTAML: biuret-modified tetraamido macrocyclic ligand) as a catalyst to perform selective oxidation of unactivated 3° bonds with unprecedented regioselectivity (3°:2° of 110:1 for adamantane oxidation), high stereoretention (99%), and turnover numbers (TONs) up to 300 using mCPBA as the oxidant. Ligand decomposition pathways involving acid-induced demetalation were identified, and this led to the development of more robust and efficient Fe-bTAML complexes that catalyzed chemoselective C-H oxidation. Mechanistic studies, which include correlation of the product formed with the FeV(O) reactive intermediates generated during the reaction, indicate that the major pathway involves the cleavage of C-H bonds by FeV(O). When these oxidations were performed in the presence of air, the yield of the oxidized product doubled, but the stereoretention remained unchanged. On the basis of 18O labeling and other mechanistic studies, we propose a mechanism that involves the dual activation of mCPBA and O2 by Fe-bTAML, leading to formation of the FeV(O) intermediate. This high-valent iron oxo remains the active intermediate for most of the reaction, resulting in high regio- and stereoselectivity during product formation.

9.
Inorg Chem ; 56(11): 6352-6361, 2017 Jun 05.
Artigo em Inglês | MEDLINE | ID: mdl-28481521

RESUMO

In this report we compare the geometric and electronic structures and reactivities of [FeV(O)]- and [FeIV(O)]2- species supported by the same ancillary nonheme biuret tetraamido macrocyclic ligand (bTAML). Resonance Raman studies show that the Fe═O vibration of the [FeIV(O)]2- complex 2 is at 798 cm-1, compared to 862 cm-1 for the corresponding [FeV(O)]- species 3, a 64 cm-1 frequency difference reasonably reproduced by density functional theory calculations. These values are, respectively, the lowest and the highest frequencies observed thus far for nonheme high-valent Fe═O complexes. Extended X-ray absorption fine structure analysis of 3 reveals an Fe═O bond length of 1.59 Å, which is 0.05 Å shorter than that found in complex 2. The redox potentials of 2 and 3 are 0.44 V (measured at pH 12) and 1.19 V (measured at pH 7) versus normal hydrogen electrode, respectively, corresponding to the [FeIV(O)]2-/[FeIII(OH)]2- and [FeV(O)]-/[FeIV(O)]2- couples. Consistent with its higher potential (even after correcting for the pH difference), 3 oxidizes benzyl alcohol at pH 7 with a second-order rate constant that is 2500-fold bigger than that for 2 at pH 12. Furthermore, 2 exhibits a classical kinteic isotope effect (KIE) of 3 in the oxidation of benzyl alcohol to benzaldehyde versus a nonclassical KIE of 12 for 3, emphasizing the reactivity differences between 2 and 3.

10.
Biomacromolecules ; 17(2): 466-75, 2016 Feb 08.
Artigo em Inglês | MEDLINE | ID: mdl-26691102

RESUMO

Nanocarriers with carbohydrates on the surface represent a very interesting class of drug-delivery vehicles because carbohydrates are involved in biomolecular recognition events in vivo. We have synthesized biocompatible miktoarm star copolymers comprising glycopolypeptide and poly(ε-caprolactone) chains using ring-opening polymerization and "click chemistry". The amphiphilic copolymers were self-assembled in water into morphologies such as nanorods, polymersomes, and micelles with carbohydrates displayed on the surface. We demonstrate that the formation of nanostructure could be tuned by chain length of the blocks and was not affected by the type of sugar residue. These nanostructures were characterized in detail using a variety of techniques such as TEM, AFM, cryogenic electron microscopy, spectrally resolved fluorescence imaging, and dye encapsulation techniques. We show that it is possible to sequester both hydrophobic as well as hydrophilic dyes within the nanostructures. Finally, we show that these noncytotoxic mannosylated rods and polymersomes were selectively and efficiently taken up by MDA-MB-231 breast cancer cells, demonstrating their potential as nanocarriers for drug delivery.


Assuntos
Portadores de Fármacos/química , Glicopeptídeos/química , Nanotubos/química , Poliésteres/química , Materiais Biocompatíveis/química , Materiais Biocompatíveis/metabolismo , Materiais Biocompatíveis/toxicidade , Linhagem Celular , Sobrevivência Celular , Química Click , Portadores de Fármacos/metabolismo , Portadores de Fármacos/toxicidade , Glicopeptídeos/metabolismo , Glicopeptídeos/toxicidade , Humanos , Interações Hidrofóbicas e Hidrofílicas , Nanotubos/toxicidade , Poliésteres/metabolismo , Poliésteres/toxicidade , Polimerização
11.
Langmuir ; 31(11): 3402-12, 2015 Mar 24.
Artigo em Inglês | MEDLINE | ID: mdl-25715114

RESUMO

Glycopolypeptide-based polymersomes have promising applications as vehicles for targeted drug delivery because they are capable of encapsulating different pharmaceuticals of diverse polarity as well as interacting with specific cell surfaces due to their hollow structural morphology and bioactive surfaces. We have synthesized glycopolypeptide-b-poly(propylene oxide) by ROP of glyco-N-carboxyanhydride (NCA) using the hydrophobic amine-terminated poly(propylene oxide) (PPO) as the initiator. This block copolymer is composed of an FDA-approved PPO hydrophobic block in conjugation with hydrophilic glycopolypeptides which are expected to be biocompatible. We demonstrate the formation of glycopolypeptide-based polymersomes from the self-assembly of glycopolypeptide-b-poly(propylene oxide) in which the presence of an ordered helical glycopolypeptide segment is required for their self-assembly into spherical nanoscale (∼50 nm) polymersomes. The polymersomes were characterized in detail using a variety of techniques such as TEM, AFM, cryo-SEM, and light-scattering measurements. As a model for drugs, both hydrophobic (RBOE) and hydrophilic (calcein) dyes have been incorporated within the polymersomes from solution. To substantiate the simultaneous entrapment of the two dyes, spectrally resolved fluorescence microscopy was performed on the glycopeptide polymersomes cast on a glass substrate. We show that it is possible to visualize individual nanoscale polymersomes and effectively probe the dyes' colocalization and energy-transfer behaviors therein as well as investigate the variation in dual-dye encapsulation over a large number of single polymersomes. Finally, we show that the galactose moieties present on the surface can specifically recognize lectin RCA120, which reveals that the polymersomes' surface is indeed biologically active.


Assuntos
Polímeros/química , Propilenoglicóis/química , Interações Hidrofóbicas e Hidrofílicas
12.
Inorg Chem ; 54(24): 11792-8, 2015 Dec 21.
Artigo em Inglês | MEDLINE | ID: mdl-26645088

RESUMO

Selective oxidation of alcohol to its corresponding carbonyl compound is an important chemical process in biological as well as industrial reactions. The heme containing enzyme CytP450 has been known to selectively oxidize alcohols to their corresponding carbonyl compounds. The mechanism of this reaction, which involves high-valent Fe(IV)(O)-porphyrin(•+) intermediate with alcohol, has been well-studied extensively both with the native enzyme and with model complexes. In this paper, we report for the first time the mechanistic insight of alcohol oxidation with Fe(V)(O) complex of biuret TAML (bTAML), which is isoelectronic with Fe(IV)(O)-porphyrin(•+) intermediate form in CytP450. The oxidations displayed saturation kinetics, which allowed us to determine both the binding constants and first-order rate constants for the reaction. The K and k values observed for the oxidation of benzyl alcohol by Fe(V)(O) at room temperature (K = 300 M(-1), k = 0.35 s(-1)) is very similar to that obtained by CytP450 compound I at -50 °C (K = 214 M(-1), k = 0.48 s(-1)). Thermodynamic parameters determined from van't Hoff's plot (ΔH∼ -4 kcal/mol) suggest hydrogen bonding interaction between substrate and bTAML ligand framework of the Fe(V)(O) complex. Analysis of H/D KIE (kH/kD ∼ 19 at 303 K), Hammett correlation and linearity in Bell-Evans-Polyanski plot points to the C-H abstraction as the rate determination step. Finally, experiments using Fe(V)(O(18)) for benzyl alcohol oxidation and use of the "radical clock" cyclobutanol as a substrate shows the absence of a rebound mechanism as is observed for CytP450. Instead, an ET/PT process is proposed after C-H abstraction leading to formation of the aldehyde, similar to what has been proposed for the heme and nonheme model compounds.

13.
Inorg Chem ; 54(13): 6112-21, 2015 Jul 06.
Artigo em Inglês | MEDLINE | ID: mdl-26053124

RESUMO

In biological oxidations, the intermediate Fe(V)(O)(OH) has been proposed to be the active species for catalyzing the epoxidation of alkenes by nonheme iron complexes. However, no study has been reported yet that elucidates the mechanism of direct O-atom transfer during the reaction of Fe(V)(O) with alkenes to form the corresponding epoxide. For the first time, we study the mechanism of O-atom transfer to alkenes using the Fe(V)(O) complex of biuret-modified Fe-TAML at room temperature. The second-order rate constant (k2) for the reaction of different alkenes with Fe(V)(O) was determined under single-turnover conditions. An 8000-fold rate difference was found between electron-rich (4-methoxystyrene; k2 = 216 M(-1) s(-1)) and electron-deficient (methyl trans-cinnamate; k2 = 0.03 M(-1) s(-1)) substrates. This rate difference indicates the electrophilic character of Fe(V)(O). The use of cis-stilbene as a mechanistic probe leads to the formation of both cis- and trans-stilbene epoxides (73:27). This suggests the formation of a radical intermediate, which would allow C-C bond rotation to yield both stereoisomers of stilbene-epoxide. Additionally, a Hammett ρ value of -0.56 was obtained for the para-substituted styrene derivatives. Detailed DFT calculations show that the reaction proceeds via a two-step process through a doublet spin surface. Finally, using biuret-modified Fe-TAML as the catalyst and NaOCl as the oxidant under catalytic conditions epoxide was formed with modest yields and turnover numbers.


Assuntos
Alcenos/química , Ferro/química , Oxigênio/química , Compostos Férricos/química , Temperatura
14.
Inorg Chem ; 54(4): 1535-42, 2015 Feb 16.
Artigo em Inglês | MEDLINE | ID: mdl-25594114

RESUMO

The presence of an Fe(V)(O) species has been postulated as the active intermediate for the oxidation of both C-H and C═C bonds in the Rieske dioxygenase family of enzymes. Understanding the reactivity of these high valent iron-oxo intermediates, especially in an aqueous medium, would provide a better understanding of these enzymatic reaction mechanisms. The formation of an Fe(V)(O) complex at room temperature in an aqueous CH3CN mixture that contains up to 90% water using NaOCl as the oxidant is reported here. The stability of Fe(V)(O) decreases with increasing water concentration. We show that the reactivity of Fe(V)(O) toward the oxidation of C-H bonds, such as those in toluene, can be tuned by varying the amount of water in the H2O/CH3CN mixture. Rate acceleration of up to 60 times is observed for the oxidation of toluene upon increasing the water concentration. The role of water in accelerating the rate of the reaction has been studied using kinetic measurements, isotope labeling experiments, and density functional theory (DFT) calculations. A kinetic isotope effect of ∼13 was observed for the oxidation of toluene and d8-toluene showing that C-H abstraction was involved in the rate-determining step. Activation parameters determined for toluene oxidation in H2O/CH3CN mixtures on the basis of Eyring plots for the rate constants show a gain in enthalpy with a concomitant loss in entropy. This points to the formation of a more-ordered transition state involving water molecules. To further understand the role of water, we performed a careful DFT study, concentrating mostly on the rate-determining hydrogen abstraction step. The DFT-optimized structure of the starting Fe(V)(O) and the transition state indicates that the rate enhancement is due to the transition state's favored stabilization over the reactant due to enhanced hydrogen bonding with water.


Assuntos
Compostos de Ferro/química , Oxigênio/química , Temperatura , Água/química , Acetonitrilas/química , Ligação de Hidrogênio , Cinética , Oxirredução , Teoria Quântica , Tolueno/química
15.
J Am Chem Soc ; 136(35): 12273-82, 2014 Sep 03.
Artigo em Inglês | MEDLINE | ID: mdl-25119524

RESUMO

Water splitting, leading to hydrogen and oxygen in a process that mimics natural photosynthesis, is extremely important for devising a sustainable solar energy conversion system. Development of earth-abundant, transition metal-based catalysts that mimic the oxygen-evolving complex of photosystem II, which is involved in oxidation of water to O2 during natural photosynthesis, represents a major challenge. Further, understanding the exact mechanism, including elucidation of the role of active metal-oxo intermediates during water oxidation (WO), is critical to the development of more efficient catalysts. Herein, we report Fe(III) complexes of biuret-modified tetra-amidomacrocyclic ligands (Fe-TAML; 1a and 1b) that catalyze fast, homogeneous, photochemical WO to give O2, with moderate efficiency (maximum TON = 220, TOF = 0.76 s(-1)). Previous studies on photochemical WO using iron complexes resulted in demetalation of the iron complexes with concomitant formation of iron oxide nanoparticles (NPs) that were responsible for WO. Herein, we show for the first time that a high valent Fe(V)(O) intermediate species is photochemically generated as the active intermediate for the oxidation of water to O2. To the best of our knowledge, this represents the first example of a molecular iron complex catalyzing photochemical WO through a Fe(V)(O) intermediate.

16.
J Am Chem Soc ; 136(27): 9524-7, 2014 Jul 09.
Artigo em Inglês | MEDLINE | ID: mdl-24387595

RESUMO

An Fe(V)(O) complex has been synthesized from equimolar solutions of (Et4N)2[Fe(III)(Cl)(biuret-amide)] and mCPBA in CH3CN at room temperature. The Fe(V)(O) complex has been characterized by UV-vis, EPR, Mössbauer, and HRMS and shown to be capable of oxidizing a series of alkanes having C-H bond dissociation energies ranging from 99.3 kcal mol(-1) (cyclohexane) to 84.5 kcal mol(-1) (cumene). Linearity in the Bell-Evans-Polayni graph and the finding of a large kinetic isotope effect suggest that hydrogen abstraction is engaged the rate-determining step.


Assuntos
Compostos de Ferro/síntese química , Oxigênio/química , Temperatura , Compostos de Ferro/química , Estrutura Molecular
17.
Biomacromolecules ; 15(10): 3679-86, 2014 Oct 13.
Artigo em Inglês | MEDLINE | ID: mdl-25122513

RESUMO

Glycopolypeptides with a defined secondary structure are of significance in understanding biological phenomena. Synthetic glycopolypeptides, or polypeptides featuring pendant carbohydrate moieties, have been of particular interest in the field of tissue engineering and drug delivery. In this work, we have synthesized charged water-soluble glycopolypeptides that adopt a helical conformation in water. This was carried out by the synthesis of a glyco-N-carboxyanhydride (glyco-NCA) containing an azide group at the sixth position of the carbohydrate ring. Subsequently, the NCA was polymerized to obtain azide-containing glycopolypeptides having good control over molecular weight and polydispersity index (PDI) in high yields. We were also able to control the incorporation of the azide group by synthesizing random co-glycopolypeptide containing 6-deoxy-6-azido and regular 6-OAc functionalized glucose. This azide functionality allows for the easy attachment of a bioactive group, which could potentially enhance the biological activity of the glycopolypeptide. We were able to obtain water-soluble charged glycopolypeptides by both reducing the azide groups into amines and using CuAAC with propargylamine. These charged glycopolypeptides were shown to have a helical conformation in water. Preliminary studies showed that these charged glycopolypeptides showed good biocompatibility and were efficiently taken up by HepG2 cells.


Assuntos
Azidas/química , Cátions/química , Glicopeptídeos/química , Glicopeptídeos/síntese química , Aminas/química , Azidas/administração & dosagem , Materiais Biocompatíveis/administração & dosagem , Materiais Biocompatíveis/química , Cátions/administração & dosagem , Linhagem Celular Tumoral , Glucose/química , Glicopeptídeos/administração & dosagem , Células Hep G2 , Humanos , Conformação Molecular , Peso Molecular , Polimerização , Polímeros/química , Água/química
18.
J Mater Chem B ; 12(36): 8952-8965, 2024 Sep 18.
Artigo em Inglês | MEDLINE | ID: mdl-39171401

RESUMO

Targeted and efficient gene delivery systems hold tremendous potential for the improvement of cancer therapy by enabling appropriate modification of biological processes. Herein, we report the design and synthesis of a novel cationic di-block copolypeptide, incorporating homoarginine (HAG) and shikimoyl (LSA) functionalities (HDA-b-PHAGm-b-PLSAn), tailored for enhanced gene transfection specifically in cancer cells. The di-block copolypeptide was synthesized via sequential N-carboxyanhydride (NCA) ring-opening polymerization (ROP) techniques and its physicochemical properties were characterized, including molecular weight, dispersity, secondary conformation, size, morphology, and surface charge. In contrast to the cationic poly-L-homoarginine, we observed a significantly reduced cytotoxic effect of this di-block copolypeptide due to the inclusion of the shikimoyl glyco-polypeptide block, which also added selectivity in internalizing particular cells. This di-block copolypeptide was internalized via mannose-receptor-mediated endocytosis, which was investigated by competitive receptor blocking with mannan. We evaluated the transfection efficiency of the copolypeptide in HEK 293T (noncancerous cells), MDA-MB-231 (breast cancer cells), and RAW 264.7 (dendritic cells) and compared it with commonly employed transfection agents (Lipofectamine). Our findings demonstrate that the homoarginine and shikimoyl-functionalized cationic di-block copolypeptide exhibits potent gene transfection capabilities with minimal cytotoxic effects, particularly in cancer cells, while it is ineffective for normal cells, indicative of its potential as a promising platform for cancer cell-specific gene delivery systems. To evaluate this, we delivered an artificially designed miRNA-plasmid against Hsp90 (amiR-Hsp90) which upon successful transfection depleted the Hsp90 (a chaperone protein responsible for tumour growth) level specifically in cancerous cells and enforced apoptosis. This innovative approach offers a new avenue for the development of targeted therapeutics with an improved efficacy and safety profile in cancer treatment.


Assuntos
Peptídeos , Transfecção , Humanos , Peptídeos/química , Peptídeos/farmacologia , Peptídeos/síntese química , Cátions/química , Células HEK293 , Camundongos , Animais , Tamanho da Partícula , Estrutura Molecular , Sobrevivência Celular/efeitos dos fármacos , Desenho de Fármacos , Linhagem Celular Tumoral
19.
Langmuir ; 29(19): 5659-67, 2013 May 14.
Artigo em Inglês | MEDLINE | ID: mdl-23578300

RESUMO

The synthesis of the amphiphilic homoglycopolypeptide was carried out by a combination of NCA polymerization and click chemistry to yield a well-defined polypeptide having an amphiphilic carbohydrate on its side chain. The amphiphilicity of the carbohydrate was achieved by incorporation of an alkyl chain at the C-6 position of the carbohydrate thus also rendering the homoglycopolypeptide amphiphilic. The homoglycopolypeptide formed multimicellar aggregates in water above a critical concentration of 0.9 µM due to phase separation. The multimicellar aggregates were characterized by DLS, TEM, and AFM. It is proposed that hydrophobic interactions of the aliphatic chains at the 6-position of the sugar moieties drives the assembly of these rod-like homoglycopolypeptide into large spherical aggregates. These multimicellar aggregates encapsulate both hydrophilic as well as hydrophobic dye as was confirmed by confocal microscopy. Finally, amphiphilic random polypeptides containing 10% and 20% α-d-mannose in addition to glucose containing a hydrophobic alkyl chain at its 6 position were synthesized by our methodology, and these polymers were also found to assemble into spherical nanostructures. The spherical assemblies of amphiphilic random glycopolypeptides containing 10% and 20% mannose were found to be surface bioactive and were found to interact with the lectin Con-A.


Assuntos
Glicopeptídeos/síntese química , Polímeros/síntese química , Tensoativos/síntese química , Glicopeptídeos/química , Estrutura Molecular , Tamanho da Partícula , Polímeros/química , Propriedades de Superfície , Tensoativos/química
20.
Biomater Sci ; 11(5): 1810-1827, 2023 Feb 28.
Artigo em Inglês | MEDLINE | ID: mdl-36655818

RESUMO

Stimuli-responsive cross-linked nanocarriers that can induce lysosomal cell death (LCD) via lysosomal membrane permeabilization (LMP) represent a new class of delivery platforms and have attracted the attention of researchers in the biomedical field. The advantages of such cross-linked nanocarriers are as follows (i) they remain intact during blood circulation; and (ii) they reach the target site via specific receptor-mediated endocytosis leading to the enhancement of therapeutic efficacy and reduction of side effects. Herein, we have synthesized a mannose-6-phosphate (M6P) based amphiphilic ABC type tri-block copolymer having two chains of FDA-approved poly(ε-caprolactone) (PCL) as the hydrophobic block, and poly(S-(o-nitrobenzyl)-L-cysteine) (NBC) acts as the photoresponsive crosslinker block. Two different tri-block copolymers, [(PCL35)2-b-NBC20-b-M6PGP20] and [(PCL35)2-b-NBC15-b-M6PGP20], were synthesized which upon successful self-assembly initially formed spherical uncross-linked "micellar-type" aggregates (UCL-M) and vesicles (UCL-V), respectively. The uncross-linked nanocarriers upon UV treatment for thirty minutes were covalently crosslinked in the middle PNBC block giving rise to the di-sulfide bonds and forming interface cross-linked "micellar-type" aggregates (ICL-M) and vesicles (ICL-V). DLS, TEM, and AFM techniques were used to successfully characterize the morphology of these nanocarriers. The dual stimuli (redox and enzyme) responsiveness of the cross-linked nanocarriers and their trafficking to the lysosome in mammalian cells via receptor-mediated endocytosis was probed using confocal microscopy images. Furthermore, the addition of a chloroquine (CQ, a known lysosomotropic agent) encapsulated cross-linked nanocarrier (CQ@ICL-V) to non-cancerous (HEK-293T) cells and liver (HepG2), and breast cancer cells (MDA-MB-231) was found to initiate lysosomal membrane permeabilization (LMP) followed by lysosomal destabilization which eventually led to lysosomal cell death (LCD). Due to the targeted delivery of CQ to the lysosomes of cancerous cells, almost a 90% smaller amount of CQ was able to achieve similar cell death to CQ alone.


Assuntos
Manosefosfatos , Polímeros , Animais , Polímeros/química , Manosefosfatos/metabolismo , Micelas , Lisossomos/metabolismo , Mamíferos
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