Chiral betulin-imino-chitosan hydrogels by dynamic covalent sonochemistry.

A series of chiral hydrogels was prepared from a homogeneous mixture of chitosan and betulinic aldehyde in different molar ratios, under the effect of ultrasound. The hydrogelation mechanism has been investigated by FTIR and CD spectroscopy, wide angle X-ray diffraction and polarized light microscopy. The morphology of hydrogels was examined by SEM.

Synthesis of novel cyclosiloxane monomers containing push-pull moieties and their anionic ring opening polymerization.

The synthesis of three novel tetracyclosiloxane monomers modified either with a nitroaniline (NA) or with a Disperse Red 1 (DR1) push-pull group and their ring opening polymerization reaction in the presence of tetramethylammonium hydroxide are presented. The prepared monomers and polymers were characterized by different spectral methods and gel permeation chromatography. For the crystalline monomers, the structures were further proven by single crystal X-ray diffraction.

Biocompatible chitosan based hydrogels for potential application in local tumour therapy.

A series of hydrogels based on chitosan polyamine and nitrosalicylaldehyde were prepared via dynamic covalent chemistry (DCC), by imination and transimination reactions towards ordered clusters which play the role of crosslinking nodes of the chitosan network. The hydrogelation mechanism has been proved through NMR and FTIR spectroscopy, X-ray diffraction and polarized light microscopy. The successful preparation of the hydrogels and their mechanical properties were further investigated using rheological measurements.

Autotemplate Microcapsules of CaCO/Pectin and Nonstoichiometric Complexes as Sustained Tetracycline Hydrochloride Delivery Carriers.

New types of composites were obtained by an autotemplate method for assembling hollow CaCO capsules by using pH-sensitive polymers. Five pectin samples, which differ in the methylation degree and/or amide content, and some nonstoichiometric polyelectrolyte complex dispersions, prepared with the pectin samples and poly(allylamine hydrochloride), were used to control the crystal growth. The morphology of the composites was investigated by scanning electron microscopy, and the polymorphs characteristics were investigated by FTIR spectroscopy.

Biopolymers/poly(ε-caprolactone)/polyethylenimine functionalized nano-hydroxyapatite hybrid cryogel: Synthesis, characterization and application in gene delivery.

Nano-hydroxyapatite (nHAp), surface functionalized with linear polyethylenimine (LPEI), was used for the preparation of biocomposites in combination with biopolymers and poly(ε-caprolactone) (PCL), by cryogelation technique, to yield biomimetic scaffolds with controlled interconnected macroporosity, mechanical stability, and predictable degradation behavior. The structural characteristics, swelling and degradation behavior of hydroxyapatite and hydroxyapatite/β-tricalcium phosphate (β-TCP) filled matrices were investigated as compared to the corresponding naked polymer 3D system. It was found that the homogeneity and cohesivity of the composite are significantly dependent on the size and amount of the included inorganic particles, which are thus determining the structural parameters.

Development of biocompatible glycodynameric hydrogels joining two natural motifs by dynamic constitutional chemistry.

The paper focusses on the synthesis of novel hydrogels by joining natural biodegradable compounds with the aim to achieve biocompatible materials for bio related applications. The hydrogels were prepared from chitosan and citral by constitutional dynamic chemistry, incorporating both molecular and supramolecular dynamic features. The hydrophobic flexible citral has been reversible immobilized onto the hydrophilic chitosan backbone via imine bonds to form amphiphilic glycodynamers, which further self-ordered through supramolecular interactions into a 3D-network of biodynameric hydrogel.

Salicyl-imine-chitosan hydrogels: Supramolecular architecturing as a crosslinking method toward multifunctional hydrogels.

Hydrogels based on chitosan and salicyladehyde were obtained by dynamic covalent chemistry. The unusual chitosan gelling in the presence of the monoaldehyde has been deciphered following and correlating data of NMR, FTIR, single crystal and wide angle XRD, POM and optical measurements. Of significant importance in understanding the crosslinking features was the synthesis of a model compound and the successfully growth as single crystal allowing the study of its supramolecular peculiarities.

Cellulose: To depolymerize… or not to?

Oxidation of the primary OH groups in cellulose is a pivotal reaction both at lab and industrial scale, leading to the value-added products, i.e. oxidized cellulose which have tremendous applications in medicine, pharmacy and hi-tech industry.

Dual crosslinked iminoboronate-chitosan hydrogels with strong antifungal activity against Candida planktonic yeasts and biofilms.

Chitosan based hydrogels are a class of cross-linked materials intensely studied for their biomedical, industrial and environmental application, but their biomedical use is limited because of the toxicity of different organic crosslinkers. To overcome this disadvantage, a new strategy to produce supramolecular chitosan hydrogels using low molecular weight compounds able to form covalent linkages and H-bonds to give a dual crosslinking is proposed. For this purpose we used 2-formylphenylboronic acid, which brings the advantage of imine stabilization via iminoboronate formation and potential antifungal activity due to the presence of boric acid residue.

Artificial water channels--incipient innovative developments.

Aquaporins (AQPs) are biological water channels known for fast water transport (∼10(8)-10(9) water molecules per s per channel), with complete proton/ion exclusion. Few synthetic channels have been designed to mimic this high water permeability and to reject ions at a significant level. This Feature Article will discuss the incipient developments of the first artificial water channel systems.

Dynameric Frameworks for DNA Transfection.

The design of performant nonviral vectors for efficient cellular DNA uptake represents a grand challenge. The variability of DNA targets and of the transfected cells limits the discovery of highly active nonviral vectors. Dynamic constitutional strategy presented here, combining easy synthesis and rapid screening, enables the selection of dynameric frameworks, DFs, for DNA transfection.

The Role of Chronic Exposure to Amoxicillin/Clavulanic Acid on the Developmental Enamel Defects in Mice.

Amoxicillin used in early childhood may be associated with enamel hypomineralization. Our aim was to assess disturbances of amelogenesis in mice lower incisors induced by chronic administration of amoxicillin/clavulanic acid (AMC). Twenty-eight C57BL/6 male mice, of similar age, randomly divided into a control and 3 treatment groups (n = 7) received subcutaneous injection, once per day, for 60 days: 50, 100, and 150 mg/kg BW of AMC.

DyNAvectors: dynamic constitutional vectors for adaptive DNA transfection.

Dynamic constitutional frameworks, based on squalene, PEG and PEI components, reversibly connected to core centers, allow the efficient identification of adaptive vectors for good DNA transfection efficiency and are well tolerated by mammalian cells.

Highly Selective Artificial Cholesteryl Crown Ether K(+)-Channels.

The bacterial KcsA channel conducts K(+) cations at high rates while excluding Na(+) cations. Herein, we report an artificial ion-channel formed by H-bonded stacks of crown-ethers, where K(+) cation conduction is highly preferred to Na(+) cations. The macrocycles aligned along the central pore surround the K(+) cations in a similar manner to the water around the hydrated cation, compensating for the energetic cost of their dehydration.

Hybrid fullerene conjugates as vectors for DNA cell-delivery.

The present study reports fullerene conjugates that act as efficient binders of double stranded DNA (dsDNA) into cytofriendly polyplexes. The conjugates are designed to generate dendrimeric structures, having C60 as the core and bearing linear or branched PEI and polyethyleneglycol (PEG) arms (∼2 kDa). Simple and reproducible synthesis pathways provided C60-PEI and C60-PEG-PEI conjugates.

Highly efficient copper(II) ion sorbents obtained by calcium carbonate mineralization on functionalized cross-linked copolymers.

A new type of Cu(II) ion sorbents is presented. These are obtained by CaCO3 mineralization from supersaturated solutions on gel-like cross-linked polymeric beads as insoluble templates. A divinylbenzene-ethylacrylate-acrylonitrile cross-linked copolymer functionalized with weakly acidic, basic, or amphoteric functional groups has been used, as well as different initial inorganic concentrations and addition procedures for CaCO3 crystal growth.

Imino-chitosan biopolymeric films. Obtaining, self-assembling, surface and antimicrobial properties.

The paper reports the preparation of twelve imino-chitosan biopolymer films by acid condensation of the amino groups of chitosan with various aldehydes, in aqueous medium, followed by slow water removal. FTIR spectroscopy has shown drastic conformation changes of chitosan macromolecular chains—from a stiff coil to a straight one, while wide angle X-ray diffraction evidenced a layered morphology of the biopolymer films. Contact angle and surface free energy determination indicated a higher biocompatibility of the new biopolymers as compared to the chitosan parent, while the microbiological screening demonstrated their self-defense properties against common and virulent pathogen agents.

Green synthesis of the silver nanoparticles mediated by pullulan and 6-carboxypullulan.

Unoxidized and carboxylated pullulan (obtained by pullulan oxidation using TEMPO-sodium hypochlorite-sodium bromide system) have been used as mediators for the silver nanoparticles formation (AgNPs), under environment-friendly conditions: using aqueous solutions, room temperature and notably, by using both mediators as reducing and stabilizing agents. The formation of AgNPs was first screened by measuring the surface plasmon resonance peak in the range of 380-440 nm using UV-vis spectroscopy. The morphology of the synthesized silver nanoparticles was determined by TEM, which indicated that the AgNPs differ on shape and thickness of the polymer shell by varying the silver nitrate concentration, different size and shape of AgNPs was achieved.

Dependence of solvent quality on the composition of copolymers: experiment and theory for solutions of P(MMA-ran-t-BMA) in toluene and in chloroform.

The interaction of toluene with P(MMA-ran-t-BMA) and with the corresponding homopolymers was determined via vapor pressure measurements at 30, 50 and 70 °C. A unified thermodynamic approach served for the modeling of the results. It is capable of describing the behavior of the different solutions by means of two adjustable parameters, one representing the effective number of solvent segments and the other accounting for the interactions between the components.

Thermodynamics of copolymer solutions: how the pair interactions contribute to the overall effect.

Vapor pressure measurements were performed for solutions of poly(methyl methacrylate-ran-tert-butyl methacrylate) with different weight fractions of tert-butyl methacrylate units, and their parental homopolymers in chloroform at 323 K, over a large domain of concentrations. The Flory-Huggins interaction parameters obtained from these experimental investigations show complex dependences of the Flory-Huggins interaction parameter on concentration and copolymer composition. This behavior can be modeled by taking into account an approach which considers the ability of the polymers to rearrange in a response to changes in their molecular surroundings [Adv.

Synthesis, characterization and solution behaviour of oxidized pullulan.

Various amounts of carboxyl groups were introduced at C-6 of the non-ionic, water soluble polysaccharide, i.e. pullulan, by applying the well-established TEMPO (2,2,6,6-tetramethylpiperidine-1-oxyl), sodium hypochlorite/sodium bromide oxidation protocol, varying the reaction time.

Cyclodextrin-poly(ε-caprolactone) based nanoparticles able to complex phenolphthalein and adamantyl carboxylate.

A new compound composed of poly(ε-caprolactone) and β-cyclodextrin (β-CD) was synthesized by click chemistry. This compound was used to obtain stable nanoparticles, which have been proven to be able to complex phenolphthalein and adamantyl carboxylate. The nanoparticles are characterized by a distinct morphology, i.

Calcium carbonate microparticle growth controlled by a conjugate drug-copolymer and crystallization time.

The influence of crystallization reaction time on CaCO3 microparticle growth from supersaturate aqueous solutions, in the presence of a conjugate drug-copolymer, has been investigated. The polymer conjugate, P(NVP-MA-Ox), is based on poly(N-vinylpyrrolidone-co-maleic anhydride) as the support and 2-amino-5-(4-methoxyphenyl)-1,3,4-oxadiazole as the drug. The microparticles are characterized by optical, scanning and transmission electron microscopy, dynamic light scattering, X-ray diffraction, flow particle image analysis and particle charge density.

Out-of-water constitutional self-organization of chitosan-cinnamaldehyde dynagels.

An investigation of the constitutional adaptive gelation process of chitosan/cinnamaldehyde (C/Cy) dynagels is reported. These gels generate timely variant macroscopic organization across extended scales. In the first stage, imine-bond formation takes place "in-water" and generates low-ordered hydrogels.