Synthesis of biocompatible nanocomposite hydrogels as a local drug delivery system

Nanocomposite biocompatible hydrogels (NCHG) were synthesised as model systems for in situ cured potentially local drug delivery devices for curing periodontal infections. The composite consists of the following components: nanoparticles (NPs), matrix gel, and chlorhexidine (CHX) as antibacterial drug. The NPs were obtained by free radical initiated copolymerization of the monomers, 2-hydroxyethyl methacrylate (HEMA) and polyethyleneglycol dimethacrylate (PEGDMA), in aqueous solution. The same monomers were used to prepare crosslinked matrices by photopolymerization. NCHGs were obtained by mixing NPs, monomers, and drug in an aqueous solution then crosslinked by photopolymerization. Mechanical properties, swelling behavior, and the kinetics of drug release have been investigated. It was found that compression strength values increased with increasing ratio of the crosslinker PEGDMA. Incorporation of NPs into the matrix resulted similar compression strength as the matrix hydrogel. The hydrated NCHGs swelled more slowly but admitted more water. The drug was incorporated in NPs by swelling in CHX aqueous solution or added to the solution of monomer mixture followed by photopolymerization. Studies of release kinetics revealed that on average 60% of the loaded drug was released. The most rapid release was observed over a 24 h period for matrix gels with low crosslinking density. For NCHGs, the release period exceeded 48 h. An unexpected result was observed for NCHGs without drug in the NPs. In this case, increasing release was observed for the first 24 h. Thereafter, however, the apparent quantity of detectable drug decreased dramatically.     

Characterization and dioxygen reactivity of a new series of coordinatively unsaturated thiolate-ligated manganese(II) complexes

The synthesis, structural, and spectroscopic characterization of four new coordinatively unsaturated mononuclear thiolate-ligated manganese(II) complexes ([Mn(II)(S(Me2)N(4)(6-Me-DPEN))](BF(4)) (1), [Mn(II)(S(Me2)N(4)(6-Me-DPPN))](BPh(4))·MeCN (3), [Mn(II)(S(Me2)N(4)(2-QuinoPN))](PF(6))·MeCN·Et(2)O (4), and [Mn(II)(S(Me2)N(4)(6-H-DPEN)(MeOH)](BPh(4)) (5)) is described, along with their magnetic, redox, and reactivity properties. These complexes are structurally related to recently reported [Mn(II)(S(Me2)N(4)(2-QuinoEN))](PF(6)) (2) (Coggins, M. K.; Kovacs, J. A. J. Am. Chem. Soc.2011, 133, 12470). Dioxygen addition to complexes 1-5 is shown to result in the formation of five new rare examples of Mn(III) dimers containing a single, unsupported oxo bridge: [Mn(III)(S(Me2)N(4)(6-Me-DPEN)](2)-(μ-O)(BF(4))(2)·2MeOH (6), [Mn(III)(S(Me2)N(4)(QuinoEN)](2)-(μ-O)(PF(6))(2)·Et(2)O (7), [Mn(III)(S(Me2)N(4)(6-Me-DPPN)](2)-(μ-O)(BPh(4))(2) (8), [Mn(III)(S(Me2)N(4)(QuinoPN)](2)-(μ-O)(BPh(4))(2) (9), and [Mn(III)(S(Me2)N(4)(6-H-DPEN)](2)-(μ-O)(PF(6))(2)·2MeCN (10). Labeling studies show that the oxo atom is derived from (18)O(2). Ligand modifications, involving either the insertion of a methylene into the backbone or the placement of an ortho substituent on the N-heterocyclic amine, are shown to noticeably modulate the magnetic and reactivity properties. Fits to solid-state magnetic susceptibility data show that the Mn(III) ions of μ-oxo dimers 6-10 are moderately antiferromagnetically coupled, with coupling constants (2J) that fall within the expected range. Metastable intermediates, which ultimately convert to μ-oxo bridged 6 and 7, are observed in low-temperature reactions between 1 and 2 and dioxygen. Complexes 3-5, on the other hand, do not form observable intermediates, thus illustrating the effect that relatively minor ligand modifications have upon the stability of metastable dioxygen-derived species.     

Oxidative addition of hydrogen halides and dihalogens to Pd. Trends in reactivity and relativistic effects

We have theoretically studied the oxidative addition of HX and X(2) to palladium for X = F, Cl, Br, I and At, using both nonrelativistic and ZORA-relativistic density functional theory at BLYP/QZ4P. The purpose is 3-fold: (i) to obtain a set of consistent potential energy surfaces (PESs) to infer accurate trends in reactivity for simple, archetypal oxidative addition reactions; (ii) to assess how relativistic effects modify these trends along X = F, Cl, Br, I and At; and (iii) to rationalize the trends in reactivity in terms of the reactants' molecular-orbital (MO) electronic structure and the H-X and X-X bond strengths. For the latter, we provide full Dirac-Coulomb CCSD(T) benchmarks. All oxidative additions to Pd are exothermic and have a negative overall barrier, except that of HF which is approximately thermoneutral and has a positive overall barrier. The activation barriers of the HX oxidative additions decrease systematically as X descends in group 17 of the periodic table; those of X(2) first increase, from F to Cl, but then also decrease further down group 17. On the other hand, HX and X(2) show clearly opposite trends regarding the heat of reaction: that of HX becomes more exothermic and that of X(2) less exothermic as X descends in group 17. Relativistic effects can be as large as 15-20 kcal/mol but they do not change the qualitative trends. Interestingly, the influence of relativistic effects on activation barriers and heats of reaction decreases for the heavier halogens due to counteracting relativistic effects in palladium and the halogens.     

Synthesis of novel type pyrazolyl and tetrazolyl isoquinolinium zwitterions

New type pyrazol‐3‐yl‐isoquinolinium hydrochloride ( 8a ) and tetrazol‐5‐yl‐isoquinolinium ( 8b ) zwitterions were synthesised. Their structures were proved by ir, pmr, cmr, ms spectra as well as X‐ray diffraction analysis of model compounds.     

A new spectrophotometric readout for the alanine-triphenyl tetrazolium chloride system for high-dose dosimetry

The electron spin resonance (ESR) readout of radical concentration in irradiated L-alanine is well known as a transfer dosimetry system, however, the high cost of the ESR equipment is a serious handicap for large-scale routine application. In this study the reaction between irradiated L-alanine powder and aqueous solution of triphenyl tetrazolium chloride (TTC) was studied. The radical produced by irradiation of alanine reacts during the dissolution with TTC forming pink-colored formazans with absorption maxima around 401 and 487 nm. This readout method can be used in the 2–200 kGy dose range.     

Metal clusters in metal/C thin film nanosystems

Structure of metal clusters and of the C₆₀ matrix in Au/C₆₀ and Cu/C₆₀ nanosystems was investigated by X-ray diffraction. Results support a charge-transfer-type interaction at the metal-C₆₀ interface, which affects the size distribution of metal clusters, favouring interstitial location of metal ions in the fullerite lattice. Received 5 February 1999 and Received in final form 7 July 1999     

ChemInform Abstract: Chemical Vapor Deposition of Gallium Nitride from the GaCl3 + NH3 System. Theoretical Study of the Structure and Thermodynamics of Potential Intermediates Formed in the Gaseous Phase.

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