Vesicle-Encapsulated Rolipram (PDE4 Inhibitor) and Its Anticancer Activity.

Vesicular carriers of drugs are popular for specific targeting and delivery. The most popular vesicles among these are liposomes. However, they suffer from some inherent limitations. In this work, alternative vesicles with enhanced stability, i.e., niosomes and bilosomes have been prepared, characterized, and their delivery efficiency studied. Bilosomes have the additional advantage of being able to withstand the harsh environment of the gastrointestinal tract (GIT). The taurine-derived bile salt (NaTC) was incorporated into the bilosome bilayer. The inspiration behind NaTC insertion is the recent reports on antiaging action and immune function of taurine. Fluorescence probing was used to study the vesicle environment. The entrapment and subsequent release of the important cAMP-specific PDE4 inhibitor/drug Rolipram, which has antibreast cancer properties, was assessed on the breast cancer cell line MCF-7. Rolipram has important therapeutic applications, one of the most significant in recent times being the treatment of Covid-19-triggered pneumonia and cytokine storms. As for cancer chemotherapy, the localization of drug, targeted delivery, and sustained release are extremely important issues, and it seemed worthwhile to explore the potential of the bilosomes and niosomes to entrap and release Rolipram. The important finding is that niosomes perform much better than bilosomes in the hormone-responsive breast cancer mileau MCF-7. Moreover, there was a 4-fold decrease in the IC50 of Rolipram encapsulated in niosomes compared to Rolipram alone. On the other hand, bilosome-encapsulated Rolipram shows higher IC50 value. The results can be further understood by molecular docking studies.

Fluorescence probing and molecular docking analysis of the binding interaction of bovine serum albumin (BSA) with the polarity probe AICCN.

In this work, the fluorescent probe 2-amino-4-(1H-indol-3-yl)-4H-chromene-3-carbonitrile (AICCN) has been used to evaluate its potential as a prospective polarity probe. From detailed fluorescence studies of the probe, it could be shown that AICCN can indeed function as an effective polarity probe. The calculated dipole moments of AICCN in both the ground state and excited state in various solvents lend support to the steady state fluorescence results. It was also shown that AICCN can be used to probe the micropolarity of micelles and can be used successfully for the determination of CMC of the surfactants. The binding process of the probe AICCN to BSA has been followed by plotting the binding isotherms and Scatchard Plots. The time-resolved fluorescence data indicate that the preferred binding site of AICCN in BSA lies close to the buried Trp residue Trp-213 in Domain II. This contention is further supported by the molecular docking studies. The interaction study of the probe AICCN with proteins is relevant for future use of AICCN as a hydrophobic drug. Information was also obtained about the effect of probe binding on the serum albumin structure, which may be correlated to its physiological activity. Thus, the probe AICCN can serve not only as a good reporter of polarity of the microenvironment in biological systems but also as an efficient fluorophore to monitor conformational changes in proteins in future.

Addressing the Superior Drug Delivery Performance of Bilosomes─A Microscopy and Fluorescence Study.

The global health scenario in present times has raised human awareness about drug delivery strategies. Among colloidal drug delivery vehicles, vesicular nanocarriers such as liposomes and niosomes are popular. However, liposomes and niosomes get disrupted in the harsh environment of the gastrointestinal tract. In this context, the drug delivery community has reported the superior performance of vesicles containing bile salts, that is, bilosomes. The present work attempts to examine the structural/morphological aspects underlying the superior performance of bilosomes. Optical microscopy, electron microscopy, and light scattering give a definite proof of the enhanced stability of bilosomes compared to niosomes, both prepared from the same amphiphilic molecule. Fluorescence probing of the vesicles provides detailed insight into the bilayer characteristics and the differences between bilosomes and niosomes. Fluorescence resonance energy transfer studies lend further support to the findings that bilosomes have a more flexible bilayer structure than niosomes. The entrapment efficiency of the vesicles for the well-known antioxidant curcumin (whose bioavailability is a matter of concern due to low water solubility) was also studied. Bilosomes show higher curcumin entrapment efficiency than niosomes. For use in drug delivery, one needs to establish a trade-off between cargo/drug entrapment and release. Thus, a flexible bilayer structure is an advantage.

Brij Niosomes as Carriers for Sustained Drug Delivery─A Fluorescence-Based Approach to Probe the Niosomal Microenvironment.

Niosomes were prepared using a triad of polyoxyethylene alkyl ether surfactants. The focus was to elucidate the effects of varying alkyl chain length and varying hydrophilic headgroups on the structure of the niosomes, with an aim to design niosomes for efficient encapsulation and release of both hydrophobic and hydrophilic drugs. The phase transitions of the surfactants were ascertained by differential scanning calorimetry. It was found that the headgroup has a profound influence on the niosomal bilayer. Fluorescent probes Coumarin 153 (C-153) and 1,6-diphenyl-1,3,5-hexatriene were used to probe the structural integrity of the niosomal bilayer under stress conditions. Other aspects of the niosomes were probed by following the aggregation of the dyes fluorescein (FL) and Nile Red, red edge excitation shift, and fluorescence resonance energy transfer (FRET) between them. Fluorescence lifetime imaging microscopy provides proof of the exact location of the donor and acceptor dyes in the niosomes under FRET condition. It was also shown that the niosomes are efficient "carriers" for entrapment and controlled release of the chemotherapeutic drug 5-fluorouracil. It was found that a rigid niosomal bilayer leads to controlled drug release. The present work is relevant for the future use of these niosomes for cargo entrapment.

Tailoring Niosomes- Implications for Controlled Cargo Release and Function as Nanoreactors.

Nonionic surfactant vesicles (Niosomes) were prepared using polyoxyethylene alkyl ether (Brij 58).The impact of variation of the Brij: cholesterol molar ratio on the niosomal structure was studied. Fluorescence studies performed with the membrane probe 1,6-Diphenyl-1,3,5-triene (DPH) gave important insight on the bilayer integrity of the niosomes in response to environmental perturbations. The aim of the work being assessment of the efficacy of the niosomes as "drug release vehicles", release studies were performed with a xanthene dye Carboxyfluorescein (CF). Further, the vesicles were used as nanoreactors for the synthesis of gold nanoparticles (GNPs) as it is often useful to house nanoparticles in biological /biomimicking environments. Stable, spherical GNPs of diameter 6-10 nm were formed in these vesicles. As the vesicular bilayer mimics the cell membrane, the present work is relevant to the use of the GNPs for diagnostic and therapeutic purpose. It has also been established that fluorescence resonance energy transfer (FRET) effectively occurs between DPH and CF in the niosomes. The FRET studies provide important insight on the location of dyes within the vesicles thus indicating the prospective applications of this fluorescence technique for tracking the location of probes in biomimicking systems which maybe extrapolated to in vivo biological systems in future.

Enhanced Hydrodynamic Radius of AOT/n-heptane/Water Reverse Micellar System Through Altered Electrostatic Interactions and Molecular Self-Assemblies.

We have demonstrated a unique approach to alter the aqueous pool size of an AOT/n-heptane/water reverse micellar system. A positively charged dye Rhodamine B (RhB) and negatively charged Rose Bengal (RB) were incorporated in the reverse micellar pool to investigate the effect of electrostatic interactions and stacking effects among the dye molecules on the AOT/n-heptane/water interface. Dynamic light scattering revealed increase in reverse micellar pool size in presence of positively charged dye aggregates at the oil-water interface. However, less expansion was observed in presence of negatively charged dye aggregates (RB). This confirms the role of electrostatic interaction in modulating the hydrodynamic radius. A head-to-tail type of stacking of RhB molecules at the interface favors this expansion. The differences in stacking of the two dyes inside the reverse micelles and their torsional mobility indicated the role of the reverse micellar interface and H-bonding ability of the microenvironment on dye aggregation. Conductivity measurements demonstrated a significant drop in percolation temperature of the reverse micellar system in presence of dye aggregates. This confirms the effect of dye aggregation and electrostatic interaction on such expansion. This strategy can be exploited for solubilizing greater amounts and a wider variety of drug molecules in microemulsions.

"Theranostic" role of bile salt-capped silver nanoparticles - gall stone/pigment stone disruption and anticancer activity.

Silver nanoparticles (AgNPs) have been synthesized in situ in micelles formed by the bile salt sodium deoxycholate (NaDC). The AgNPs exhibit "green" fluorescence. It has been shown in the present study that they can disrupt the components of gall stones/pigment stones. This unique ability of the AgNPs has been observed upon detailed study of the interaction between the endobiotic pigment bilirubin (BR) and bile salt (NaDC). In addition, these AgNPs show significant cytotoxicity towards the breast cancer cells (MCF-7). Thus the AgNPs synthesized in this work show important physiological activity and can serve as prospective "Theranostic Materials" in future. Their green fluorescence bears relevance to future diagnostic applications while their anticancer activity and disruptive action upon BR aggregates in bile salt micelles is extremely important for therapeutic purpose. This is the first report of the use of metal nanoparticles in disruption of components of gall stones/pigment stones and thus the present work has very important physiological significance. The detailed spectral studies indicate that bile salts increase the dimerization of BR which could be linked to increased solubilisation of BR in bile salt media and consequent bile stone/pigment stone formation. Importantly, an increase in red fluorescence was observed (upon dimerization of BR), which is important for cancer detection and studying the metabolism of biological tissues.

Probing the Highly Efficient Electron Transfer Dynamics between Zinc Protoporphyrin IX and Sodium Titanate Nanosheets.

Sodium titanate nanosheets (NaTiO2 NS) have been prepared by a new method and completely characterized by TEM, SEM, XRD, EDX, and XPS techniques. The sensitization of nanosheets is carried out with Zn protoporphyrin IX (ZnPPIX). The emission intensity of ZnPPIX is quenched by NaTiO2 NS, and the dominant process for this quenching has been attributed to the process of photoinduced electron injection from excited ZnPPIX to the nanosheets. Time resolved fluorescence measurement was used to elucidate the process of electron injection from the singlet state of ZnPPIX to the conduction band of NaTiO2 NS. Electron injection from the dye to the semiconductor is very fast (ket ≈ 10(11) s(-1)), much faster than previously reported rates. The large two-dimensional surface offered by the NaTiO2 NS for interaction with the dye and the favorable driving force for electron injection from ZnPPIX to NaTiO2 NS (ΔGinj = -0.66 V) are the two important factors responsible for such efficient electron injection. Thus, NaTiO2 NS can serve as an effective alternative to the use of TiO2 nanoparticles in dye sensitized solar cells (DSSCs).

Green synthesis of gold nanoparticles for staining human cervical cancer cells and DNA binding assay.

Gold nanoparticles have been functionalized by non-ionic surfactants (polysorbates) used in pharmaceutical formulations. This results in the formation of more well-dispersed gold nanoparticles (GNPs) than the GNPs formed in neat water. The synthesized GNPs show good temporal stability. The synthesis conditions are mild and environmentally benign. The GNPs can bind to ct-DNA and displace bound dye molecules. The DNA-binding assay is significant as it preliminarily indicated that DNA-GNP conjugates can be formed. Such conjugates are extremely promising for applications in nanobiotechnology. The GNPs can also stain the human cervical cancer (HeLa) cells over a wide concentration range while remaining non-cytotoxic, thus providing a non invasive cell staining method. This result is very promising as we observe staining of HeLa cells at very low GNP concentrations (1 µM) while the cell viability is retained even at 10-fold higher GNP concentrations.

Ultraslow recombination in AOT-capped TiO2 nanoparticles sensitized by protoporphyrin IX.

Aerosol OT (AOT) capped TiO2 nanoparticles have been prepared by a phase transfer mechanism. The TiO2 nanoparticles have a diameter of 5-10 nm, are highly crystalline (anatase) and show high photoluminescence. They are effectively sensitized by protoporphyrin IX (PPIX) and show high electron injection rates while the rate of back recombination is much slower than those reported previously. Thus the AOT capped TiO2 nanoparticles synthesized in this work are highly effective not only in promoting ultrafast electron injection from PPIX to TiO2 but more importantly they lead to extremely slow back recombination rates. The significance of this work is in the synthesis of highly photoluminescent TiO2 nanoparticles which can be easily sensitized by a porphyrin dye, whereby ultraslow recombination is observed.

Control of the size and shape of TiO2 nanoparticles in restricted media.

Template-capped TiO2 nanostructures have been synthesized. In certain template conditions, TiO2 hexagons are found to form. These hexagonal structures can be effectively sensitized by fluorescein dye without any change in the protonation state of the dye. Bare TiO2 nanoparticles are not so useful for sensitization with dyes like fluorescein as they alter the dye protonation state. The novelty of this work is twofold-the hitherto elusive hexagonal phase of TiO2 nanoparticles has been stabilized and the synthesis of TiO2 in the rutile phase has been achieved under mild conditions.

Facile and general preparation of multifunctional main-chain cationic polymers through application of robust, efficient, and orthogonal click chemistries.

Poly(ß-hydroxyl amine)s are prepared from readily available small molecular building blocks at ambient conditions. These macromolecules can be transformed into main-chain cationic polymers upon quaternization of the backbone amine units. The modular and mild nature of the synthesis allows for incorporation of multiple (2-4) chemically distinct reactive sites in the polymer chain. Modifications of the reactive sites afford multifunctional polymers with tunable properties. The orthogonal nature of the involved chemistries sets the synthetic pathway free from any functional group protection/deprotection requirements. This feature also allows for alteration of the modification sequence.

Synthesis of gold nanoparticles in niosomes.

This work outlines a novel method for the synthesis of stable gold nanoparticles within the spatially confined region of vesicles. For the first time, Span/cholesterol based niosomes have been used for nanoparticle synthesis. The restricted geometry within niosomes prevents nanoparticle aggregation. The results have important implications for controlled delivery of nanoparticles for therapeutic applications.

Efficient synthesis of multifunctional polymers via thiol-epoxy "click" chemistry.

We demonstrate high efficiency and simplicity of the thiol-epoxy reaction towards preparation of a wide range of main-chain as well as end-chain multifunctional polymers.

Synthesis and self-assembly of dynamic covalent block copolymers: towards a general route to pore-functionalized membranes.

A diblock copolymer is designed to have incompatible blocks, unsymmetrical block lengths, and a reversible linkage. This copolymer self-assembles into nanostructured cylindrical morphology in thin films. Removal of the nanosized cylinders by breaking the reversible linkage then affords nanoporous membranes featuring a chemically reactive functionality in the pores.

Folding of a donor-containing ionene by intercalation with an acceptor.

Cationic ionenes that bear electron-rich 1,5-dialkoxynaphthalene (DAN) units within the alkylene segment were allowed to interact with different types of electron-deficient, acceptor-containing molecules in an effort to realize intercalation-induced folding of the ionenes; the collapse of the chains was expected to occur in such a way that the donor and acceptor units become arranged in an alternating fashion. Several acceptor-bearing molecules were prepared by the derivatization of pyromellitic dianhydride and naphthalene tetracarboxylic dianhydride with two different oligoethylene glycol monomethyl ether monoamines. This yielded acceptor molecules with different water solubility and allowed the examination of solvophobic effects in the folding process. UV/Vis spectroscopic studies were carried out by using a 1:1 mixture of the DAN-ionenes and different acceptor molecules in water/DMSO solvent mixtures. The intensity of the charge-transfer (CT) band was seen to increase with the water content in the solvent mixture, thereby suggesting that the intercalation is indeed aided by solvophobic effects. The naphthalene diimide (NDI) bearing acceptor molecules consistently formed significantly stronger CT complexes when compared to the pyromellitic diimide (PDI) bearing acceptor molecules, which is a reflection of the stronger π-stacking tendency of the former. AFM studies of drop-cast films of different ionene-acceptor combinations revealed that compact folded structures are formed most effectively under conditions in which the strongest CT complex is formed.

Phenyl-ring-bearing cationic surfactants: effect of ring location on the micellar structure.

A series of isomeric cationic surfactants (S1-S5) bearing a long alkyl chain that carries a 1,4-phenylene unit and a trimethyl ammonium headgroup was synthesized; the location of the phenyl ring within the alkyl tail was varied in an effort to understand its influence on the amphiphilic properties of the surfactants. The cmc's of the surfactants were estimated using ionic conductivity measurements and isothermal calorimetric titrations (ITC); the values obtained by the two methods were found to be in excellent agreement. The ITC measurements provided additional insight into the various thermodynamic parameters associated with the micellization process. Although all five surfactants have exactly the same molecular formula, their micellar properties were seen to vary dramatically depending on the location of the phenyl ring; the cmc was seen to decrease by almost an order of magnitude when the phenyl ring was moved from the tail end (cmc of S1 is 23 mM) to the headgroup region (cmc of S5 is 3 mM). In all cases, the enthalpy of micellization was negative but the entropy of micellization was positive, suggesting that in all of these systems the formation of micelles is both enthalpically and entropically favored. As expected, the decrease in cmc values upon moving the phenyl ring from the tail end to the headgroup region is accompanied by an increase in the thermodynamic driving force (ΔG) for micellization. To understand further the differences in the micellar structure of these surfactants, small-angle neutron scattering (SANS) measurements were carried out; these measurements reveal that the aggregation number of the micelles increases as the cmc decreases. This increase in the aggregation number is also accompanied by an increase in the asphericity of the micellar aggregate and a decrease in the fractional charge. Geometric packing arguments are presented to account for these changes in aggregation behavior as a function of phenyl ring location.

Oxovanadium(IV) complexes of phenanthroline bases: the dipyridophenazine complex as a near-IR photocytotoxic agent.

Oxovanadium(iv) complexes [VOCl(B)(2)]Cl (1-3) of phenanthroline bases (B), viz. 1,10-phenanthroline (phen in ), dipyrido[3,2-d:2',3'-f]quinoxaline (dpq in ) and dipyrido[3,2-a:2',3'-c]phenazine (dppz in ), have been prepared, characterized and their DNA and protein binding, photo-induced DNA and protein cleavage activity and photocytotoxicity have been studied. Complex , structurally characterized by X-ray crystallography, shows the presence of a vanadyl group in VOClN(4) coordination geometry. The dpq ligand displays a chelating mode of binding with a N-donor site trans to the oxo-group. The chloride ligand is cis to the oxo-group. The one-electron paramagnetic complexes show a d-d band near 715 nm in 15% DMF-Tris-HCl buffer. The complexes are redox active exhibiting a V(iv)/V(iii) redox couple within -0.5 to -0.7 V vs. SCE in 20% DMF-Tris-HCl/0.1 M KCl. The complexes bind to calf thymus (CT) DNA in the order: (dppz) > (dpq) > (phen). The binding data reveal the groove and/or partial intercalative DNA binding nature of the complexes. The complexes show "chemical nuclease" activity in the dark in the presence of 3-mercaptopropionic acid or hydrogen peroxide via a hydroxyl radical pathway. The dpq and dppz complexes are efficient photocleavers of DNA in UV-A light of 365 nm forming reactive singlet oxygen ((1)O(2)) and hydroxyl radical ( OH) species. Complexes and also show DNA cleavage activity in red light (>750 nm) by an exclusive OH pathway. The complexes display a binding propensity to bovine serum albumin (BSA) protein giving K(BSA) values in the range of 7.1 x 10(4)-1.8 x 10(5) M(-1). The dppz complex shows BSA and lysozyme protein cleavage activity in UV-A light of 365 nm via OH pathway. The dppz complex exhibits significant PDT effect in human cervical cancer HeLa cells giving IC(50) values of 1.0 microM and 12.0 microM in UV-A and visible light, respectively (IC(50) = >100 microM in the dark).

Geminate charge recombination in alternating polyfluorene copolymer/fullerene blends.

By measuring excited state and charge dynamics in blends of an alternating polyfluorene copolymer and fullerene derivative over nine orders in time and two orders in light intensity, we have monitored the light-induced processes from ultrafast charge photogeneration to much slower decay of charges by recombination. We find that at low light intensities relevant to solar cell operation relatively fast (approximately 30 ns) geminate recombination is the dominating charge decay process, while nongeminate recombination has a negligible contribution. The conclusion of our work is that under solar illumination conditions geminate recombination of charges may be directly competing with efficient charge collection in polymer/fullerene solar cells.