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The interaction of nanometric synthetic materials with cell membranes is one of the key factors determining their possible cytotoxicity. This work investigated the interaction of polycation nanostructures with lipid and cellular membranes. The nanostructures (polymer micelles) were formed in aqueous media as a result of the self-assembly of strong amphiphilic polycations containing hydrophobic alkyl groups of various lengths. The effect of alkyl length on micellization and its influence on the physicochemical properties and biological activity of the polycations were analyzed. Next, the cytotoxicity of the polycations was assessed using human skin fibroblasts (HSFs). The results show that the ability of the polycations to form pores in biomembranes decreases with the length of the attached alkyl groups. The polycations substituted with short alkyl groups were the most cytotoxic, which correlates well with their high capacity to open pores in biomembranes. However, they can perforate the fibroblast plasma membrane at non-toxic concentrations. Overall, our results show that the observed trends in cytotoxicity cannot be fully explained within simple interactions between polycationic micelles and cell membranes. A relationship does, however, seem to exist between polycation membrane activity (pore formation) and its cytotoxicity.

Novel, structurally stable hybrid magnetic materials based on polymers of natural origin and containing superparamagnetic iron oxide nanoparticles (SPIONs) were obtained. SPIONs coated with the chitosan derivative were linked with the chitosan-collagen hydrogel matrix by the covalent bonds formed between the macromolecules of nanoparticles' coating and matrix on their crosslinking with genipin. The systems obtained were structurally stable as confirmed by turbidity studies. Their microstructure was determined by electron microscopy studies (SEM). The homogenic distribution of SPIONs in hybrid materials was observed by Scanning Transmission Electron Microscopy (STEM). Magnetic force microscopy (MFM) confirmed the magnetic properties of hybrids and SPIONs distribution within the samples. The rheological studies allowed to determine the effect of hybrid material composition on their mechanical properties (storage modulus). Magnetic characterization confirmed that SPIONs preserved their superparamagnetic properties in the hybrid materials fabricated.

Novel multifunctional biomimetic injectable hybrid systems were synthesized. The physicochemical as well as biological in vitro and in vivo tests demonstrated that they are promising candidates for bone tissue regeneration. The hybrids are composed of a biopolymeric collagen/chitosan/hyaluronic acid matrix and amine group-functionalized silica particles decorated with apatite to which the alendronate molecules were coordinated. The components of these systems were integrated and stabilized by cross-linking with genipin, a compound of natural origin. They can be precisely injected into the diseased tissue in the form of a viscous sol or a partially cross-linked hydrogel, where they can serve as scaffolds for locally controlled bone tissue regeneration/remodeling by supporting the osteoblast formation/proliferation and maintaining the optimal osteoclast level. These materials lack systemic toxicity. They can be particularly useful for the repair of small osteoporotic bone defects.

Curcumin, a natural product with recognized antiviral properties, is limited in its application largely due to its poor solubility. This study presents the synthesis of water-soluble curcumin-poly(sodium 4-styrenesulfonate) (Cur-PSSNan) covalent conjugates. The antiflaviviral activity of conjugates was validated in vitro by using the Zika virus as a model. In the development of these water-soluble curcumin-containing derivatives, we used the macromolecules reported by us to also hamper viral infections. Mechanistic investigations indicated that the conjugates exhibited excellent stability and bioavailability. The curcumin and macromolecules in concerted action interact directly with virus particles and block their attachment to host cells, hampering the infection process.

Background: Herpes Simplex (HSV) viruses are widely spread, highly contagious human pathogens. The statistics indicate that 50-90% of adults worldwide are seropositive for these viruses, mainly HSV-1 and HSV-2. The primary infection results in the appearance of watery blisters (cold sores) on the skin, lips, tongue, buccal mucosa or genitals. The ocular infection is the major cause of corneal blindness in the Western World. Once the HSV virus enters human body, it cannot be completely eradicated because HSV viruses are able to change into their latent form which can survive the treatment. The viron resides in trigeminal ganglia of the host, who becomes vulnerable to the reoccurrence of the disease during the whole lifespan. The neurotropic and neuro-invasive properties of HSV are responsible for neurodegenerative illnesses, such as Alzheimer's disease. Acyclovir and its analogues, being the inhibitors of the viral DNA replication, are the only approved medicines for HSV infection therapies. Objective: The current paper presents the up-to-date overview of the important pharmacological features of acyclovir, its analogues and their delivery systems including the mechanism of action, routes of administration, absorption and metabolism, as well as side effects of the therapy. Conclusion: Acyclovir remains the gold standard in the treatment of herpes virus infections, mainly due to the emerging of the new delivery systems improving considerably its bioavailability. The analogues of acyclovir, especially their esters, characterized by significantly higher bioavailability and safety, may gradually replace acyclovir in selected applications.

A series of aza‐BODIPY dyes substituted with meta‐(dimethylamino)phenyl groups were synthesized and their spectroscopic, photophysical, and electrochemical properties were compared. Highly desirable photophysical and photochemical properties were induced in meta‐(Me2N)Ph‐substituted aza‐BODIPY by bromination of the aromatic rings at the 3 and 5 positions. In particular, high values of singlet oxygen quantum yields (ΦΔ) were measured, ranging from 0.36 to 0.58. The photosensitized oxygenation process of a model compound – diphenylisobenzofuran (DPBF) ‐ proceeds via a Type II mechanism for the di‐bromo derivative, while for the tetra‐bromo derivative a mixed mechanism involving both 1O2and other reactive forms of oxygen formation (Type I and/or Type III) was detected. Nanosecond laser photolysis experiments of the brominated aza‐BODIPYs revealed T1→Tnabsorption spanning from ca. 350 nm to ca. 510 nm with the triplet lifetimes (τT) ranged between 15.6 μs and 26.0 μs. The brominated aza‐BODIPYs studied exhibited an absorption band within the so‐called “therapeutic window”, with λabslocated between 620 nm and 636 nm. As estimated by CV/DPV measurements, the meta‐(Me2N)Ph‐substituted aza‐BODIPYs studied exhibited a multi‐electron oxidation processes at a relatively low oxidation potentials (Eox), pointing to the very good electron‐donating properties of these molecules. All compounds studied exhibited extremely high photostability and thermal stability. Heavy atoms: High singlet‐oxygen quantum yields obtained for brominated aza‐BODIPY derivatives were obtained. This study indicates they can be photocatalysts and photosensitizers for biomedical applications.

A series of poly(ethylene glycol)-block-poly(3-(methacryloylamino)propyl trimethylammonium chloride) (PEG-b-PMAPTAC) water-soluble block copolymers consisting of PEG and PMPTAC were obtained by reversible addition–fragmentation chain-transfer (RAFT) polymerization and demonstrated to function as highly effective herpes simplex virus type 1 (HSV-1) inhibitors as shown by in vitro tests (Vero E6 cells) and in vivo experiments (mouse model). Half-maximal inhibitory concentration (IC50) values were determined by quantitative polymerase chain reaction to be 0.36 ± 0.08 μg/mL for the most effective polymer PEG45-b-PMAPTAC52and 0.84 ± 1.24 μg/mL for the less effective one, PEG45-b-PMAPTAC74. The study performed on the mouse model showed that the polymers protect mice from lethal infection. The polymers are not toxic to the primary human skin fibroblast cells up to the concentration of 100 μg/mL and to the Vero E6 cells up to 500 μg/mL. No systemic or topical toxicity was observed in vivo, even with mice treated with concentrated formulation (100 mg/mL). The mechanistic studies indicated that polymers interacted with the cell and blocked the formation of the entry/fusion complex. Physicochemical and biological properties of PEGx-b-PMAPTACymake them promising drug candidates.

Polycations are an attractive class of macromolecules with promising applications as drug/gene carriers and biocides. The chemical structure and concentration of a polycation determine its interaction with cellular membranes and, hence, are crucial parameters for designing efficient nontoxic polycations. However, the interaction of polycations with biomembranes at the molecular level and the corresponding free-energy landscape is not well understood. In this work, we investigate the molecular mechanism of interaction between a strong polycation substituted with alkyl moieties and zwitterionic membranes via long-time-scale all-atom molecular dynamics simulations and free-energy calculations combined with Langmuir monolayer, atomic force microscopy, and calcein-release experimental measurements. We found that the membrane activity of the polycation and its ability to induce pores in the membranes can be attributed to the polycation-induced changes in the bilayer organization, such as reduced membrane thickness, increased disorder of the acyl chains, reduced packing, and electrostatic field gradients between membrane leaflets. These changes facilitate the penetration of water into the membrane and the formation of aqueous defects/pores. The calculated free-energy profiles indicate that the polycation lowers the nucleation barrier for pore opening and the free energy for pore formation in a concentration-dependent manner. Above the critical coverage of the membrane, the polycation nucleates spontaneous pores in zwitterionic membranes. Our work demonstrates the potential of combining enhanced sampling methods in MD simulations with experiments for a quantitative description of various events in the polycation-membrane interaction cycle, such as strong adsorption on the membrane due to hydrophobic and electrostatic interactions, and pore formation.

Mid-infrared absorption spectroscopy has been used extensively to study the molecular properties of cell membranes and model systems. Most of these studies have been carried out on macroscopic samples or on samples a few micrometers in size, due to constraints on sensitivity and spatial resolution with conventional instruments that rely on far-field optics. Properties of membranes on the scale of nanometers, such as in-plane heterogeneity, have to date eluded investigation by this technique. In the present work, we demonstrate the capability to study single bilayers of phospholipids with near-field mid-infrared spectroscopy and imaging and achieve a spatial resolution of at least 40 nm, corresponding to a sample size of the order of a thousand molecules. The quality of the data and the observed spectral features are consistent with those reported from measurements of macroscopic samples and allow detailed analysis of molecular properties, including orientation and ordering of phospholipids. The work opens the way to the nanoscale characterization of the biological membranes for which phospholipid bilayers serve as a model.

Di- and triblock copolymers with low dispersity of molecular weight were synthesized using radical addition–fragmentation chain transfer polymerization. The copolymers contained anionic poly(sodium 2-acrylamido-2-methylpropanesulfonate) (PAMPS) block as an anticoagulant component. The block added to lower the toxicity was either poly(ethylene glycol) (PEG) or poly(2-(methacryloyloxy)ethyl phosphorylcholine) (PMPC). The polymers prolonged clotting times both in vitro and in vivo. The influence of the polymer architecture and composition on the efficacy of anticoagulation and safety parameters was evaluated. The polymer with the optimal safety/efficacy profile was PEG47-b-PAMPS108, i.e., a block copolymer with the degrees of polymerization of PEG and PAMPS blocks equal to 47 and 108, respectively. The anticoagulant action of copolymers is probably mediated by antithrombin, but it differs from that of unfractionated heparin. PEG47-b-PAMPS108 also inhibited platelet aggregation in vitro and increased the prostacyclin production but had no antiplatelet properties in vivo. PEG47-b-PAMPS108 anticoagulant activity can be efficiently reversed with a copolymer of PEG and poly((3-(methacryloylamino)propyl)trimethylammonium chloride) (PMAPTAC) (PEG41-b-PMAPTAC53, HBC), which may be attributed to the formation of polyelectrolyte complexes with PEG shells without anticoagulant properties.

Nanoparticles made of amphiphilic block copolymers comprising biodegradable core-forming blocks are very attractive for the preparation of drug-delivery systems with sustained release. Their therapeutic applications are, however, hindered by low values of the drug-loading content (DLC). The compatibility between the drug and the core-forming block of the copolymer is considered the most important factor affecting the DLC value. However, the molecular picture of the hydrophobic drug–copolymer interaction is still not fully recognized. Herein, we examined this complex issue using a range of experimental techniques in combination with atomistic molecular dynamics simulations. We performed an analysis of the interaction between itraconazole, a model hydrophobic drug, and a poly(ethylene glycol)–poly(lactide-co-glycolide) (PEG–PLGA) copolymer, a biodegradable copolymer commonly used for the preparation of drug-delivery systems. Our results clearly show that the limited capacity of the PEG–PLGA nanoparticles for the accumulation of hydrophobic drugs is due to the fact that the drug molecules are located only at the water–polymer interface, whereas the interior of the PLGA core remains empty. These findings can be useful in the rational design and development of amphiphilic copolymer-based drug-delivery systems.

Itraconazole (ITZ) is an antifungal agent used clinically to treat mycotic infections. However, its therapeutic effects are limited by low solubility in aqueous media. Liposome-based delivery systems (LDS) have been proposed as a delivery mechanism for ITZ to alleviate this problem. Furthermore, PEGylation, the inclusion in the formulation of a protective “stealth sheath” of poly(ethylene glycol) around carrier particles, is widely used to increase circulation time in the bloodstream and hence efficacy. Together, these themes highlight the importance of mechanistic and structural understanding of ITZ incorporation into liposomes both with and without PEGylation because it can provide a potential foundation for the rational design of LDS-based systems for delivery of ITZ, using alternate protective polymers or formulations. Here we have combined atomistic simulations, cryo-TEM, Langmuir film balance, and fluorescence quenching experiments to explore how ITZ interacts with both pristine and PEGylated liposomes. We found that the drug can be incorporated into conventional and PEGylated liposomes for drug concentrations up to 15 mol % without phase separation. We observed that, in addition to its protective properties, PEGylation significantly increases the stability of liposomes that host ITZ. In a 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) bilayer without PEGylation, ITZ was found to reside inside the lipid bilayer between the glycerol and the double-bond regions of POPC, adopting a largely parallel orientation along the membrane surface. In a PEGylated liposome, ITZ partitions mainly to the PEG layer. The results provide a solid basis for further development of liposome-based delivery systems.

ABSTRACTNovel sulfonated derivatives of poly(allylamine hydrochloride) (NSPAHs) and N-sulfonated chitosan (NSCH) have been synthesized, and their activity against influenza A and B viruses has been studied and compared with that of a series of carrageenans, marine polysaccharides of well-documented anti-influenza activity. NSPAHs were found to be nontoxic and very soluble in water, in contrast to gel-forming and thus generally poorly soluble carrageenans. In vitroand ex vivostudies using susceptible cells (Madin-Darby canine kidney epithelial cells and fully differentiated human airway epithelial cultures) demonstrated the antiviral effectiveness of NSPAHs. The activity of NSPAHs was proportional to the molecular mass of the chain and the degree of substitution of amino groups with sulfonate groups. Mechanistic studies showed that the NSPAHs and carrageenans inhibit influenza A and B virus assembly in the cell.

The paper presents the recent advances in the development and studies of multifunctional nanoparticles which can be used to prevent/cure the cardiovascular diseases by detecting, treating and monitoring the early stages of atherosclerotic and thrombotic changes in endothelium.

The paper presents the recent advances in the development and studies of multifunctional nanoparticles which can be used to prevent/cure the cardiovascular diseases by detecting, treating and monitoring the early stages of atherosclerotic and thrombotic changes in endothelium.

A new type of hybrid photosensitizer (Po–C30B) was obtained by efficient adsorption of a 5,10,15,20-tetrakis(4-carboxyphenyl)porphyrin (Po) by Cloisite 30B (C30B)a monotallow bis(hydroxyethyl)ammonium-modified montmorillonite clayfrom acidic solution in methanol. Structural and spectroscopic properties of Po-nanoclay photosensitizer were determined using X-ray diffraction, laser scanning fluorescence confocal microscopy, and electronic absorption/emission spectroscopies. Po is present not only at the surface of the nanoclay but also in the interior of the Po-C30B hybrid material. The obtained material was found to be an efficient photosensitizer for the oxidation of phenol in aqueous solution under irradiation with the visible light (λ > 470 nm). The mechanism and the quantum yield of that process were shown to be strongly pH-dependent. They were controlled by the acid–base equilibria of porphyrin associated with imine N-protonation as well as by the ionization of the phenol molecule. The quantitative information regarding these dependencies was obtained. The values of K3and K4acid–base equilibrium constants were determined (pK3= 5.88 and pK4= 2.46) from the absorption spectra recorded during acid–base titration and using an evolutionary factor analysis with the mathematical model including dicationic (H2Po2+), monocationic (HPo+), and neutral (Po) porphyrin forms. They were used to evaluate the importance of these forms in singlet oxygen generation by Po–C30B under defined pH conditions. Moreover, the hybrid photosensitizer can be used repeatedly, which makes it possible to use it in industrial applications.

Micellar multilayer films were prepared from an amphiphilic comb-like polycation (“polysoap”) and the polyanion poly(styrene sulfonate) (PSS) using alternate polyelectrolyte layer-by-layer (LbL) self-assembly. Linear growth of the film thickness was evidenced by UV–vis spectroscopy and spectroscopic ellipsometry. Imaging by atomic force microscopy (AFM) indicated that the micellar conformation adopted by the polycation in solutions was preserved in the films. Thus, hydrophobic photoactive molecules, which were solubilized by the hydrophobic nanodomains of the micellar polymer prior to deposition, could be transferred into the films. Photoinduced energy transfer was observed in the nanostructured multilayers between naphthalene (donor) and perylene (acceptor) molecules embedded inside the polymer micelles. The efficiency of the energy transfer process can be controlled to some extent by introducing spacer layers between the layers containing the donor or acceptor, revealing partial stratification of the micellar LbL films. Also, photoinduced electron transfer was evidenced between perylene (donor) and butyl viologen (acceptor) molecules embedded inside the multilayers by steady-state fluorescence spectroscopy. The obtained photoactive nanostructures are promising candidates for solar-to-chemical energy conversion systems.

The purpose of this work was to study two methods of degradation of roxithromycin: acidic hydrolysis and photocatalytic degradation under illumination with near-UV light in the presence of the TiO2photosensitizer. For acidic degradation studies a TLC-densitometric method has been developed using TLC aluminium plates precoated with silica gel F254and the mobile phase composed of methanol–acetone–ammonia 25% (1 : 14 : 0.1, v/v/v) which gives compact spots for roxithromycin and its degradation products. Photocatalytic degradation studies in the presence of TiO2were monitored by HPLC. The obtained results have shown that both methods of degradation of roxithromycin are quite efficient. Kinetics of the first order photocatalytic degradation reaction follows the Langmuir–Hinshelwood theory for photocatalytic microheterogeneous systems. The chemical structures of the degradation products obtained during acidic degradation and photocatalytic degradation were suggested based on the UPLC-MS/MS technique. The general mechanisms of both processes were proposed.

Photodynamic therapy (PDT) is a clinically approved method for treatment of cancer, microbial infections, and some other diseases. PDT has proved effective in the treatment of malignancies of various organs, including lung, bladder, gastrointestinal tract, and skin, and in the therapy of bacterial infection of skin wounds and carious lesions. It employs a combination of light and a drug (photosensitizer, PS) to induce phototoxicity against cancerous cells or bacteria. The efficiency of currently used PSs is limited due to their hydrophobic nature, which causes aggregation of the PS in aqueous media and low tumor selectivity (a low value of the tumor-to-normal tissue ratio). The purpose of this review is to present some aspects of the current state of knowledge on nanostructural carriers for the PS delivery. In this paper we reviewed studies on the development of nanostructural materials for PDT, especially those based on the polymeric and liposomal formulation of PS. We focused mainly on the nanostructural PSs obtained by the covalent attachment of hydrophilic polymer chain to the low-molecular-weight PS, the incorporation of PS into polymeric nanostructures such as micelles, and the solubilization of PS in liposome carriers.

The properties of heparin, a key anticoagulant, are reviewed. The important issues in heparinotherapy, i.e., reaching quick anticoagulant effect, maintaining therapeutic level of anticoagulation, heparin inhibition and non-invasive heparin formulations have been reviewed and discussed, with the focus on the role of polymeric substances in the proposed solutions.

The mechanisms and factors causing or influencing degenerative diseases require tailor-made solutions. Natural polysaccharides are among the most versatile building units of the novel drug delivery systems. Their properties can be easily tailored to specific needs because they depend not only on the first-order structure, but also on the molecular weight, the type of end-groups and the conformation of the chain. The review presents the current state-of-art in the field of modifications of natural polysaccharides aiming at improving the delivery of anti-degenerative agents. Derivatization includes introducing of ionic or hydrophobic groups in order to adjust polarity or to obtain amphiphilic material, as well as degradable bonds, spacers and targeting moieties. The influence of the modification on the properties of the carrier, such as its size, surface charge, encapsulation efficiency, drug release profile, and stability in vivo, is discussed. Application of the polysaccharide derivatives to enhance the mucoadhesion and to actively target the drug to its site of action is also shown for a variety of carriers: nano and microparticulate systems, coated liposomes, hollow particles and polymer-drug conjugates.

Summary:Block amphiphilic copolymer, poly(sodium styrenesulfonate‐block‐5‐(4‐acryloyloxyphenyl)‐10,15,20‐tritolylporphyrin) (PSSS‐block‐Po) was synthesized by nitroxide‐mediated controlled radical polymerization. The polymer is soluble in water and can absorb light in the visible region. The absorbed energy migrates between the porphyrin chromophores. The polymer chains form nanospheres in aqueous solution. Their interiors are highly hydrophobic and can effectively solubilize the large hydrophobic molecules of the various organic compounds (pyrene, azulene, rubrene). The polymer photosensitizes oxidation of organic compounds via photoinduced electron transfer and/or via formation of singlet oxygen. The effect of the architecture, chain properties and Po content on the photochemical properties of the porphyrin‐containing photosensitizers was also discussed.

Summary:This work presents a novel surfactant‐free method of preparation of silicone hollow nano/microstructures in water. New silicone monomer was synthesized by attaching the unsaturated fatty acid ester – methyl 10‐undecenoate (UDM) to the commercial silicone monomer ‐ 1,3,5,7‐tetramethylcyclotetrasiloxane (D4H) using hydrosilylation reaction. The reaction was catalyzed by Karstedt's catalyst [Pt(0)‐divinyltetramethyldisiloxane complex]. That modified monomer, tetra(11‐methoxy‐11‐oxoundecyl)‐tetramethylcyclotetrasiloxane (D4undecyl), undergoes self‐organization in water. The anionic ring‐opening polymerization of D4undecylresulted in formation of the silicone polymer (poly‐D4undecyl). Both, the silicone monomer and the polymer were dispersed in aqueous medium using sonication. The structures in the dispersions were visualized by cryo‐transmission electron microscopy (Cryo‐TEM) and optical microscopy. The size of the particles was also determined from dynamic light scattering (DLS) measurements.

Photodynamic theraphy (PDT) is a clinically approved method for treatment of cancer and some other diseases. It employs the combination of a drug (photosensitizer) and light to induce photoxicity towards the cancerous cells. The efficiency of currently used photosensitizers is limited due to their aggregation in aqueous media and low chemical purity; usually a mixture of various isomers is used. This paper presents the results of our studies on the development of nanostructural materials for PDT. They are constructed from porphyrin (Po) which is covalently attached to the chain of hydrophylic polymer such as poly(methacrylic acid) (PMA) or poly(ethylene glycol) (PEG) and solubilized in lipid bilayer of liposome vesicles. The attachment of Po to the polymer chain improves its solubility in water while the solubilization in liposome carriers helps the dye to penetrate the cell membranes. Physicochemical and photophysical properties of those systems were determined. The in vitrostudies on cancer cell lines demonstrated that the photosensitizers are efficiently accumulated in the cells. Their dark toxicity is negligible, while phototoxicity is very high.

Summary: Series of novel water‐soluble photosensitizers based on dextran was synthesized and studied. Dextran was modified by covalent attachment of anthracene chromophores. Photophysical and photochemical properties of the photosensitizers in aqueous solutions were determined. Their applicability for sensitization of oxidation of polynuclear aromatics and degradation of pesticides was demonstrated. Removal of photosensitizers from the environment after their usage was discussed.

The thermosensitive polyelectrolytes were obtained by grafting 2‐acrylamido‐2‐methyl‐1‐propanesulfonic acid (AMPS) onto hydroxypropylcellulose (HPC), a biodegradable polysaccharide. The interactions of the polymers with dodecyltrimethylammonium chloride (DTAC), a model cationic surfactant, were studied. It was found by the measurements of the surface tension and the analysis of fluorescence emission of pyrene used as a fluorescent probe, that the HPC–AMPS graft polymers strongly interact with DTAC with the formation of polymer–surfactant complexes. The critical aggregation concentrations of these polymer–surfactant systems were found to be of the order of 10−5 mol/dm3. The polymers were found to be potentially useful in the purification of water from cationic surfactants. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 2401–2407, 2006

A copolymer of poly(vinyl naphthalene) grafted onto poly(vinyl alcohol) has been synthesized with nitroxide‐mediated controlled radical polymerization. By separating the processes of the generation of grafting sites and polymerization, we can avoid the formation of the homopolymer. Because of its architecture, the polymer is soluble in water, despite the high content of hydrophobic groups. The naphthalene chromophores tend to aggregate, forming hydrophobic microdomains in an aqueous solution. Those aggregates exist in a very constrained environment that leads to extraordinarily large redshifts of both the absorption and emission of the polymer. The polymer acts as an efficient photosensitizer in photoinduced electron transfer. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 2675–2683, 2006

Novel water‐soluble polymeric photosensitizers (SPO) based on starch and containing porphyrin chromophores were synthesized and studied. The polymers were soluble in water and in dimethyl sulfoxide. Photophysical studies and solubilization of molecular probes proved the formation of hydrophobic, rigid microdomains in an aqueous solution of SPO; they were created due to the clustering of porphyrin chromophores attached to the polymer chain. SPO polymers absorbed light from the UV‐visible spectral region. The polymers could sensitize photochemical reactions mediated by electron transfer, energy transfer or both, from the singlet‐excited state of porphyrin chromophores to the molecules of organic compounds solubilized in the hydrophobic microdomains or residing in the water phase.

Summary:We demonstrate a novel approach for constructing photoactive multilayer films in which the aggregation of fluorescing molecules is effectively eliminated. In the films formed via a layer‐by‐layer electrostatic self‐assembly technique, the core‐shell amphiphilic copolymer, poly[(sodium 4‐styrenesulfonate)‐block‐vinylnaphthalene], was deposited. The isolated cores served as nanosized host sites for photoactive guest molecules (pyrene, perylene). The efficient energy transfer between polymeric chromophores and perylene molecules was observed.

The interactions between copolymers of sodium styrene sulfonate (SSS) and N-isopropylacrylamide (NIPAM), anionic polyelectrolytes, and dodecyltrimethylammonium chloride (DTAC), a cationic surfactant, were studied in aqueous solutions of various ionic strengths. The copolymers were found to be thermoresponsive, showing a lower critical solution temperature (LCST). The influence of the polymer composition, the surfactant concentration, and the ionic strength on the LCST was studied. The surfactant was found to interact strongly with the polymer, forming mixed polymer-surfactant micelles. The critical aggregation concentration (cac) of the polymer-surfactant system was found from fluorescence spectroscopy using pyrene as a fluorescent probe. A strong dependence of the anionic polyelectrolyte-cationic surfactant interactions on the structure of the ionic comonomer was observed.

A series of copolymers of acrylic acid, N‐isopropylacrylamide (NIPAM), and cinnamoyloxyethyl acrylate were synthesized and studied. The polymers were responsive to four stimuli: UV light, temperature, pH, and ionic strength. The polymeric cinnamoyl chromophores underwent efficient photodimerization with concomitant photocrosslinking of the polymeric micelles. Because of the content of NIPAM, the terpolymers displayed a lower critical solution temperature, which could be controlled by the polymer composition, pH, and ionic strength. The ability to respond to the pH resulted from the content of acrylic carboxyl groups, which became protonated at low pHs. The changes in the polymer properties due to the application of the aforementioned stimuli were studied with pyrene and perylene as fluorescent probes. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 3879–3886, 2004