Spectroscopic Study of the Interaction of Carboxyl-Modified Gold Nanoparticles with Liposomes of Different Chain Lengths and Controlled Drug Release by Layer-by-Layer Technology.

In this article, we investigate the interactions of carboxyl-modified gold nanoparticles (AuC) with zwitterionic phospholipid liposomes of different chain lengths using a well-known membrane probe PRODAN by steady-state and time-resolved spectroscopy. We use three zwitterionic lipids, namely, dipalmitoylphosphatidylcholine (DPPC), 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC), and 1,2-dilauroyl-sn-glycero-3-phosphocholine (DLPC), which are widely different in their phase transition temperatures to form liposome-AuC assemblies. The steady-state and time-resolved studies indicate that the AuC brings in stability toward liposomes by local gelation. We observe that the bound AuC detach from the surface of the liposomes under pH ≈ 5 due to protonation of the carboxyl group, thus eliminating the electrostatic interaction between nanoparticles and head groups of liposomes. The detachment rate of AuC from the liposome-AuC assemblies is different for the aforementioned liposomes due to differences in their fluidity. We exploited the phenomena for the controlled release of a prominent anticancer drug Doxorubicin (DOX) under acidic conditions for different zwitterionic liposomes. The drug release rate was further optimized by coating of liposome-AuC assemblies with oppositely charged polymer (P), polydiallyldimethylammonium chloride, followed by a mixture of lipids L (DMPC:DMPG) and again with a polymer in a layer-by-layer fashion to obtain capsule-like structures. This system is highly stable for weeks, as confirmed by field-emission scanning electron microscopy (FE-SEM) and confocal laser scanning microscopy (CLSM) imaging, and inhibits premature release. The layer coating was confirmed by hydrodynamic size and zeta potential measurements of the systems. The capsules obtained are of immense importance as they can control release of the drug from the systems to a large extent.

A robust synthesis of functionalized 2H-indazoles via solid state melt reaction (SSMR) and their anti-tubercular activity.

A facile and convenient approach has been developed for the synthesis of functionalized indazoles via solid state melt reaction using easily accessible starting materials under catalyst-free conditions. This transformation involves electrocyclization via a conjugated nitrene intermediate obtained under thermal conditions. Further anti-tubercular activity screening of the molecules was undertaken, among the compounds 3a-3x screened for in vitro antimycobacterial activity against Mycobacterium tuberculosis H37Rv, compound 3u (MIC: 4.20µM) was found to be most active and are superior over existing standard drugs ciprofloxacin and ethambutol. Compounds 3c and 3x were found to equally potent as ethambutol. Among most potent compounds in the series, four compounds (3n, 3o, 3p and 3u) showed lower cytotoxicity which could be promising drug candidates for further development.

Interaction of Different Divalent Metal Ions with Lipid Bilayer: Impact on the Encapsulation of Doxorubicin by Lipid Bilayer and Lipoplex Mediated Deintercalation.

In this article, we investigate the influence of different metal ions (Ca2+, Mg2+, and Zn2+) on binding of an anticancer drug doxorubicin (DOX) to DMPC bilayer and lipoplex mediated deintercalation of DOX from DOX-DNA complex. Our study reveals that lipid bilayer in the presence of different metal ions displays much higher binding affinity toward DOX than bare lipid bilayer does. Further, this affinity for a particular metal ion increases linearly with metal ion concentration. The steady state and time-resolved fluorescence studies reveal that binding of DOX with lipid bilayer in the presence of different metal ions varies in the order of Ca2+> Mg2+> Zn2+. The rotational relaxation of DOX in the presence of different metal ions takes place in the same order. We explain these phenomena in the light of alteration of the physical properties brought about by metal ions. Moreover, we find that binding pattern of metal ions with lipid head groups influences the intake of DOX in lipid bilayer. We exploit the binding of DOX with bilayer to study the deintercalation of DOX from DOX-DNA complex. We observe that with increase in metal ion concentration the deintercalation increases. Among all metal ions, Ca2+ appears to be most effective in deintercalation compared to other metal ions. The time-resolved fluorescence anisotropy and circular dichroism measurements indicate that in the presence of Ca2+, lipid bilayer offer strongest interaction with DNA while the same is weakest for Zn2+. This explains the highest percentage of deintercalation of DOX from drug-DNA complex in the presence of Ca2+. Overall the present study demonstrates a new strategy that binding of drug molecules with lipid bilayer and deintercalation of the same from drug-DNA complex can be tuned by modulation of lipid bilayer with different metal ions and their concentration.

Lipoplex-Mediated Deintercalation of Doxorubicin from Calf Thymus DNA-Doxorubicin Complex.

In this paper, we report the lipoplex-mediated deintercalation of anticancer drug doxorubicin (DOX) from the DOX-DNA complex under controlled experimental conditions. We used three zwitterionic liposomes, namely, 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC), 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC), and 2-oleoyl-1-palmitoyl-sn-glycero-3-phosphocholine (POPC), which are widely different in their phase transition temperatures to form a lipoplex with calf thymus DNA in the presence of Ca(2+) ions. The study revealed that DPPC being in sol-gel phase was more effective in releasing the drug from the DOX-DNA complex compared with liposomes that remain in liquid crystalline phase (DMPC and POPC). The higher extent of drug release in the case of DPPC liposomes was attributed to the stronger lipoplex formation with DNA as compared with that of other liposomes. Owing to the relatively smaller head group area, the DPPC liposomes in their sol-gel phase can absorb a larger number of Ca(2+) ions and hence offer a strong electrostatic interaction with DNA. This interaction was confirmed by time-resolved anisotropy and circular dichroism spectroscopy. Apart from the electrostatic interaction, the possible hydrophobic interaction between the liposomes and DNA was also taken into account for the observed deintercalation. The successful uptake of drug molecules by liposomes from the drug-DNA complex in the post-release period was also confirmed using confocal laser scanning microscopy (CLSM).

Smart Approach for In†Situ One-Step Encapsulation and Controlled Delivery of a Chemotherapeutic Drug using Metal-Organic Framework-Drug Composites in Aqueous Media.

Controlled release of an anticancer drug, doxorubicin (dox), from metal-organic framework (MOF)-drug composites is demonstrated under different external stimuli. 1,3,5-Benzenetricarboxylic acid (H3 BTC) is used as an organic ligand, and iron acetate and zinc nitrate are used as metal sources to synthesize Fe-BTC and Zn-BTC MOFs, which are known to be biocompatible. The in situ formation of MOF-drug composites demonstrates high drug loading capacity compared to conventional methods. The present methodology is devoid of any extra steps for loading the drug after synthesis. Moreover, the drug loading is also independent of pore size of the MOF as the drug molecules are embedded inside the MOF during their in situ formation. The drug release was monitored under external stimuli including change to acidic pH and the presence of biocompatible liposomes for a period of more than 72 h. Steady-state fluorescence spectroscopy is used to monitor the drug release as a function of time and confocal laser scanning microscopy is used to unravel the post-release fate of doxorubicin in the presence of liposomes. It is found that drug release rate is higher for the Zn-BTC-dox composite than for the Fe-BTC-dox composite. This is attributed to the stronger binding between dox and Fe-BTC than that between dox and Zn-BTC. This study highlights a novel approach for the preparation of MOF-drug composites in an aqueous medium for future biomedical applications.

First Evidence of the Liposome-Mediated Deintercalation of Anticancer Drug Doxorubicin from the Drug-DNA Complex: A Spectroscopic Approach.

Biocompatible liposomes were used for the first time to study the deintercalation process of a prominent anticancer drug, doxorubicin (DOX), from doxorubicin-intercalated DNA (DOX-DNA complex) under controlled experimental conditions. The study revealed that anionic liposomes (DMPG liposomes) appeared to be the most effective to bring in the highest percentage of drug release while cationic liposomes (DOTAP liposomes) scored the lowest percentage of release. The drug release was primarily attributed to the electrostatic interaction between liposomes and drug molecules. Apart from this interaction, changes in the hydrophobicity of the medium upon addition of liposomes to the DNA-drug solution accompanied by lipoplex formation between DNA and liposomes were also attributed to the observed deintercalation. The CD and the time-resolved rotational relaxation studies confirmed that lipoplex formation took place between liposomes and DNA owing to electrostatic interaction. The confocal study revealed that in the postrelease period, DOX binds with liposomes. The reason behind the binding is electrostatic interaction as well as the unique bilayer structure of liposomes which helps it to act as a "hydrophobic sink" for DOX. The study overall highlighted a novel strategy for deintercalation of drug using biocompatible liposomes, as the release of the drug can be controlled over a period of time by varying the concentration and composition of the liposomes.

Zeolitic Imidazole Framework (ZIF) Nanospheres for Easy Encapsulation and Controlled Release of an Anticancer Drug Doxorubicin under Different External Stimuli: A Way toward Smart Drug Delivery System.

The conventional drug delivery systems made from organic- or inorganic-based materials suffer from some problems associated with uncontrolled drug release, biocompatibility, cytotoxicity, and so forth. To overcome these problems, zeolitic imidazole framework (ZIF) hybrid materials can be one of the solutions. Here, we report a very easy and successful encapsulation of an anticancer drug doxorubicin inside two ZIFs, namely, ZIF-7 and ZIF-8, which are little explored as drug delivery systems, and we studied the controlled release of the drug from these two ZIFs under external stimuli such as change in pH and upon contact with biomimetic systems. Experimental results demonstrate that ZIF-7 remains intact when the pH changes from physiological condition to acidic condition, whereas ZIF-8 successfully releases drug under acidic condition. Interestingly, both the ZIFs are excellent for drug release when they come in contact with micelles or liposomes. In the case of ZIF-8, the drug delivery can be controlled for 3 h, whereas its analogue ZIF-7 delivers the drug for a time span of 10 h. We explained the reluctance of ZIF-7 toward drug release in terms of rigidity. This study highlights that by using different ZIFs and liposomes, the drug release rate can be easily modulated, which implies ample possibility for ZIFs as a good drug delivery system. The study shows a novel strategy for easy drug encapsulation and its release in a controlled manner, which will help future development of the drug delivery system.

Interaction of different prototropic species of an anticancer drug ellipticine with HSA and IgG proteins: multispectroscopic and molecular modeling studies.

Studies on interactions between an anticancer alkaloid, ellipticine, and various carrier proteins in blood serum show tangible results to gain insight into the solubility and transport of the drug under physiological conditions. In this report, we extensively studied the interactions of different prototropic species of ellipticine with two prominent serum proteins namely human serum albumin (HSA) and immunoglobulin G (IgG) in their native and partially unfolded states using steady state and time resolved fluorescence spectroscopy, molecular docking and circular dichroism (CD). Both the fluorescence techniques and molecular modeling studies elucidate that only neutral species of ellipticine binds to HSA in the sudlow site II. Unlike HSA, IgG in the native state mostly binds to cationic species of ellipticine. However, in partially unfolded configuration, IgG binds to the neutral ellipticine molecules. Molecular docking studies indicate the prevalence of electrostatic interactions involving charged residues in the binding process of cationic species of ellipticine with native IgG in its Fab region. In native conformation, the hydrophobic residues of the Fab region are found to be buried completely by the ligand. This implies that the hydrophobic interaction will be favored by unfolding of IgG through which the hydrophobic pocket will be more accessible to neutral species of ellipticine. The circular dichroism measurements reveal that upon interaction with ellipticine, heat and acid treated HSA resumes its α-helical content. This conclusive comparative study on interactions of IgG and HSA with ellipticine yields the result that native HSA is responsible for transport of neutral species of ellipticine whereas IgG carries cationic ellipticine in its native form.

Controlled release of a sparingly water-soluble anticancer drug through pH-responsive functionalized gold-nanoparticle-decorated liposomes.

The binding and detachment of carboxyl-modified gold nanoparticles from liposomes is used for controlled drug delivery. This study reveals that the binding and detachment of nanoparticles from liposomes depends on the degree of hydration of the liposomes. Liposomes with a lower hydration level undergo stronger electrostatic interactions with negatively charged gold nanoparticles, thus leading to a slower detachment of the carboxyl-modified gold nanoparticles under gastric conditions. Therefore, under gastric conditions, gold-nanoparticle-decorated dipalmitoylphosphatidylcholine (DPPC) liposomes exhibit an at least ten-times-slower drug release compared to gold-nanoparticle-decorated 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) liposomes, although both liposomes in the bare state fail to pursue controlled release. Our study also reveals that one can modulate the drug-release rate by simply varying the concentration of nanoparticles. This study highlights a novel strategy for the controlled release of drug molecules from liposomes.

Partitioning of prototropic species of an anticancer drug ellipticine in bile salt aggregates of different head groups and hydrophobic skeletons: a photophysical study to probe bile salts as multisite drug carriers.

The entrapment of neutral and cationic species of an anticancer drug, namely ellipticine and their dynamic features in different bile salt aggregates have been investigated for the first time using steady state and time-resolved fluorescence spectroscopy. Because ellipticine exists in various prototropic forms under physiological conditions, we performed comparative photophysical and dynamical studies on these prototropic species in different bile salts varying in their head groups and hydrophobic skeletons. We found that the initial interaction between ellipticine and bile salts is governed by the electrostatic forces where cationic ellipticine is anchored to the head groups of bile salts. Bile salts having conjugated head groups are better candidates to bind with the cationic species than those having the non-conjugated ones. The fact implies that binding of cationic species to different bile salts depends on the pK(a) of the corresponding bile acids. The hydrophobic interaction dominates at higher concentrations of bile salts due to formation of aggregates and results in entrapment of neutral ellipticine molecules according to their hydrophobicity indices. Thus bile salts act as multisite drug carriers. The rotational relaxation parameters of cationic ellipticine were found to be dependent on head groups and the number of hydroxyl groups on the hydrophilic surface of bile salts. Cationic ellipticine exhibits a faster rotational relaxation in the tri-hydroxy bile salt aggregates than in di-hydroxy bile salts. We interpreted this observation from the fact that tri-hydroxy bile salts hold a higher number of water molecules in their hydrophilic surface offering a less viscous environment for ellipticine compared to di-hydroxy bile salts. Surprisingly, the neutral ellipticine molecules display almost the same rotational relaxation in all the bile salts. The observation indicates that after intercalation inside the hydrophobic pocket, neutral ellipticine molecules experience similar confinement in all the bile salts.