New types of hydrogels have been obtained starting from high bloom purified gelatin A, alone or in mixtures with hyaluronan and with a hyaluronan derivative bearing primary amino groups, by ...transglutaminase-catalyzed cross-linking. The reticulation process, carried out adopting two different temperature protocols, and the ensuing materials have been characterized in terms of rheologically estimated gel times, equilibrium swelling in water and in phosphate buffer solution (PBS), and rigidity modulus. Main structural and conformational factors governing the physicochemical properties and the possible application of the new hydrogels are discussed.
Controlled polymerization of N‐isopropylacrylamide (NIPAAM) was achieved by atom transfer radical polymerization (ATRP) using ethyl 2‐chloropropionate (ECP) as initiator and ...CuCl/tris(2‐dimethylaminoethyl)amine (Me6TREN) as a catalytic system. The polymerization was carried out in DMF:water 50:50 (v/v) mixed solvent at 20 °C. The first order kinetic plot was linear up to 92% conversion. Controlled molecular weights up to 2.2 × 104 and low polydispersities (1.19) were obtained. The living character of the polymerization was also demonstrated by self‐blocking experiments. Block copolymers with N,N‐dimethylacrylamide (DMAAM) and 3‐sulfopropyl methacrylate (SPMA) were successfully prepared.
Molecular weights and polydispersities of polyNIPAAM versus NIPAAM conversion for two different degrees of polymerization.
Guar gum (GG) has been partially methyl-etherified under heterogeneous reaction conditions. The resulting products, (methyl ether guar: MG) with different degrees of substitution, have been ...characterized by means of viscosity,
1H NMR, and FTIR measurements. The introduction of methoxyl groups along the polysaccharidic chains reduces the hydrogen bonding sites on the guar backbone reducing primarely the extent of hydrogen bonding between guar macromolecules, hence their aggregation tendency. A comparative analysis of Mark–Houwink–Sakurada parameters and of the characteristic ratio (
C
∞) of GG and MG samples in aqueous solution has been carried out using the Burchard–Stockmayer–Fixman method for flexible and semiflexible chains. The MG chains exhibit more flexibility than those of native guar gum which is traceable to a disruption of intrachain hydrogen bonds.
Clenbuterol molecularly imprinted polymers (MIPs) as chromatographic stationary phase for the solid-phase extraction (SPE) of the drug from biological samples have been prepared. Propylene columns ...filled with 500 mg of clenbuterol MIPs have been tested with respect to their loading capacity, memory effects, selectivity toward related drugs (mabuterol, clenproperol, clenisopenterol, ritodrine) and specificity toward interferences arising from heterogeneous matrices such as animal feeds, bovine urine and liver. Analytes were concentrated on Extrelut 20 columns and the residues resuspended in 70% acetonitrile. Application, washing and elution fractions were collected and analyzed by HPLC–diode array detection. Results indicate this MIP approach in SPE is extremely selective for clenbuterol, mabuterol, clenproperol and clenisopenterol (>95% found in the eluate), with a loading capacity of about 20 μg/100 mg of stationary phase. Ritodrine showed a recovery rate of 51%. The molecular recognition mechanism is so specific to allow clenbuterol detection and identification by conventional detectors at level of interest (ppb) also from complex matrices such as feeds, urine and liver.
Boron neutron capture therapy (BNCT) represents a promising approach for tumor therapy. A critical requirement for BNCT is tumor targeting, a goal that is currently addressed with the development of ...low and high molecular weight agents capable of interacting with receptors expressed by cancer cells. Here, we describe a new bioconjugate (HApCB) composed by n-propyl carborane linked to hyaluronan (HA) via an ester linkage for a degree of substitution of approximately 30%, leading to a water-soluble derivative. The structure and main physicochemical characteristics of the new HA derivative were determined by means of Fourier transform infrared, fluorescence, and 1H, 13C, and 10B NMR analysis and are herein reported in detail. As HA is recognized by the CD44 antigen, densely populating the surface of many tumor cells, HApCB is expected to deliver boron atoms from the locally released carborane cages directly to target cells for antitumor application in BNCT. In vitro biological experiments showed that HApCB was not toxic for a variety of human tumor cells of different histotypes, specifically interacted with CD44 as the native unconjugated HA, and underwent uptake by tumor cells, leading to accumulation of amounts of boron atoms largely exceeding those required for a successful BNCT approach. Thus, HApCB may be regarded as a promising new BNCT agent for specific targeting of cancer cells overexpressing the CD44 receptor.
Two new HA derivatives bearing carborane rings were synthesized by click chemistry. The optimal conditions were assessed for the preparation of biocompatible boron carriers, potentially suitable for ...application in BNCT and capable of targeting the CD44 antigen. The new polymeric samples were characterized by means of NMR‐spectroscopy techniques that gave degrees of 17 and 8% for HAAACB and HapACB, respectively. Both HAAACB and HApACB turned out to be nontoxic for colorectal, ovarian and bladder tumor cell lines, to disclose a specific interaction with the CD44 antigen as the native hyaluronan moiety, and to deliver boron‐atom concentrations largely sufficient for BNCT therapy when accumulated in cancer cells.
A novel procedure for the in situ rapid chemical gelation of aqueous solutions of hyaluronan has been employed. In brief, water-soluble polysaccharide derivatives bearing side chains endowed with ...either azide or alkyne terminal functionality have been prepared. When the latter two types of derivatives are mixed together in aqueous solution they give rise to a 1,3-dipolar cycloaddition reaction resulting in fast gelation (in the presence of catalytic amounts of Cu(I)) at room temperature. Gel formation has been characterized rheologically and could also be followed qualitatively by means of IR spectroscopy. The resulting gels have been studied in terms of swelling properties and, in particular, NMR spectral features. Carrying out the gelation process in aqueous solutions of benzidamine and doxorubicin, respectively, the polysaccharide networks acted as drug reservoirs. The doxorubicin release resulted in well controllable acting upon the gels degree of cross-linking. Finally, formation of the click-gels using aqueous suspensions of Saccharomices cerevisiae yeast cells allowed the obtainment of scaffolds inside which cells were homogeneously distributed and smoothly adhered to the inner pores surfaces, according to SEM analysis. After 24 h about 60% of the entrapped cells exhibited proliferating activity. Click-gels prepared as detailed herein do have a number of positive features that make them, in perspective, materials of choice for drug release and tissue engineering manipulations.
Guar gum, a β-d-(1→4)-linked d-mannan with α-d-galactopyranosyl units attached as side groups, was treated with α-galactosidase, an enzyme that splits off the α-d-galactosyl units to obtain a ...galactomannan with a low galactose content. The galactose-depleted polysaccharide was then selectively oxidized in C(6) position and epimerized using mannuronan C(5)-epimerases, namely AlgE1, AlgE4, AlgE6, and their mixtures, obtaining new pseudo-alginates. In this paper, we report a full high field 1D and 2D NMR study of guar gum as such and of the galactose-depleted, oxidized and epimerized compounds, respectively. From the 1H NMR spectra, the degree of epimerization, the distribution of mannuronic acid (M) and guluronic acid (G) residues and the average G-block length, NG>1, were obtained. By means of NMR diffusion experiments, it was also shown that no significant degradation of the polysaccharide occurs as a consequence of the epimerization reactions.
After an introductory note on the main reasons underlying the interest in microbial polysaccharides as subjects of fundamental structural/physicochemical investigations, as well as of applied ...studies, and after a brief historical account, a survey is offered of ongoing research activities in Europe in the broad field of carbohydrate polymers of microbial origin. Attention is drawn to glycopolymers of actual or potential industrial relevance.
Highly selective non-covalent clenbuterol (CL) imprinted polymers were prepared using methacrylic acid as monomer and ethylene glycol dimethacrylate as cross-linking agent. HPLC experiments with ...columns packed with this material showed that CL are selectively recognised with respect to all other adrenergic substances studied using a phosphate buffer/acetonitrile eluent. The separation was strongly dependent on pH and the organic/aqueous phase ratio. An important contribution to the recognition mechanism from hydrophobic interactions was found at higher water content. These results demonstrate that a novel family of absorbents with high selectivity for CL was obtained which can be exploited in solid phase extractions or as recognition elements for selective sensors.
