Nonlinear post-compression in multi-pass cells in the mid-IR region using bulk materials.

We numerically investigate the regime of nonlinear pulse compression at mid-IR wavelengths in a multi-pass cell (MPC) containing a dielectric plate. This post-compression setup allows for ionization-free spectral broadening and self-compression while mitigating self-focusing effects. We find that self-compression occurs for a wide range of MPC and pulse parameters and derive scaling rules that enable its optimization. We also reveal the solitonic dynamics of the pulse propagation in the MPC and its limitations and show that spatiotemporal/spectral couplings can be mitigated for appropriately chosen parameters. In addition, we reveal the formation of spectral features akin to quasi-phase matched degenerate four-wave mixing. Finally, we present two case studies of self-compression at 3-µm and 6-µm wavelengths using pulse parameters compatible with driving high-field physics experiments. The simulations presented in this paper set a framework for future experimental work using few-cycle pulses at mid-IR wavelengths.

Polymeric drugs based on random copolymers with antimitotic activity.

Polymeric drugs based on random copolymers with antimitotic activity were obtained by free radical copolymerization of oleyl 2-acetamido-2-deoxy-α-d-glucopyranoside methacrylate (OAGMA) and 2-ethyl-(2-pyrrolidone) methacrylate (EPM) at low and high conversion and analyzed in terms of microstructure, physicochemical, and biological properties. Reactivity ratios of monomers were found to be r(OAGMA) = 1.34 and r(EPM) = 0.98, indicating the obtaining of statistical copolymers with random sequence distribution of the comonomeric units in the macromolecular chains. The glass transition temperature of the copolymers presents a negative deviation from the predicted values according to the Fox equation, suggesting a higher flexibility of the alternating diad. Copolymeric systems with OAGMA contents between 10-50 mol % presented thermosensitive behavior in a heating process showing cloud point temperatures (CPT) in the range 45-28 °C with increasing OAGMA content and hysteresis in one heating-and-cooling cycle. In vitro glycolipid release studies revealed the stability of the ester group in culture medium. The polymeric drugs with 30 and 50 mol % OAGMA presented antimitotic activity on a human glioblastoma line, but they were less toxic on normal human fibroblast cultures.

Eugenol functionalized poly(acrylic acid) derivatives in the formation of glass-ionomer cements.

Eugenol possesses analgesic and anti-inflammatory properties with the ability to relieve pain in irritated or diseased tooth pulp, thus, incorporating polymers with eugenol moieties in dental cements is attractive. An acrylic derivative of eugenyl methacrylate (EgMA) was copolymerized with acrylic acid (AA) using a radical initiator, to yield a water soluble copolymer of acrylic acid and eugenyl methacrylate {p(AA-co-EgMA)}, which was then applied in the formulation of glass-ionomer cements for potential application as dental cements. Three concentrations of the p(AA-co-EgMA) copolymer in water were studied by, 30wt%, 40wt% and 50wt%, and used with different powder:liquid ratios to formulate the glass-ionomer cements. The setting kinetics showed that both the concentration of the copolymer and the powder:liquid ratio influenced the working and setting times. Thus, selected formulations were used for further characterization of their mechanical properties, water uptake and fluoride release, to optimize the cement formulation. The experimental glass-ionomer cements exhibited physical and mechanical properties in compliance to ISO standard requirements with the benefit of the initial pH being greater than the commercial formulation used as the standard cement. Furthermore, the presence of the eugenyl moieties bound to the polymer matrix was advantageous with respect to moisture sensitivity and anti-bacterial properties.

Acrylic injectable and self-curing formulations for the local release of bisphosphonates in bone tissue.

Two bisphosphonates (BPs), namely 1-hydroxy-2-[4-aminophenyl]ethane-1,1-diphosphonic acid (APBP) and 1-hydroxy-2-[3-indolyl]ethane-1,1-diphosphonic acid (IBP), have been synthesized and incorporated to acrylic injectable and self-curing formulations. Alendronic acid monosodium trihydrated salt (ALN) containing cement was formulated as control. These systems have potential applications in low density hard tissues affected by ailments characterized by a high osteoclastic resorption, i.e. osteoporosis and osteolysis. Values of curing parameters of APBP and IBP were acceptable to obtain pastes with enough fluency to be injected through a biopsy needle into the bone cavity. Working times ranged between 8 and 15 min and maximum temperature was around 50 degrees C. Cured systems stored for a month in synthetic body fluid had compressive strengths between 90 and 96 MPa and modulus between 1.2 and 1.3 GPa, which suggest mechanical stabilization after setting and in the short time. BPs were released in PBS at an initial rate depending on the corresponding chemical structure in the order ALN > APBP > IBP to give final concentrations in PBS of 2.21, 0.44, and 0.19 mol/mL for ALN, APBP, and IBP, respectively. Cytotoxicities of bisphosphonates were evaluated, IC(50) values being in the order APBP > ALN > IBP. Absence of cytotoxicity coming from leachables of the cured systems was observed in all cases independently of the BP. An improved cell growth and proliferation for the systems loaded with APBP and IBP compared with that loaded with ALN was observed, as assessed by measuring cell adhesion and proliferation, and total DNA content.

A novel amphiphilic acrylic copolymer based on Triton X-100 for a poly(alkenoate) glass-ionomer cement.

OBJECTIVES: The aim of this study was to synthesize a novel ampiphilic polyalkenoic acid copolymer based on acrylic acid and a methacrylic macromonomer of Triton X-100 and determine the efficacy of the novel copolymeric polyalkenoic acid in the formation of glass-ionomer cements. METHODS: Two water soluble copolymers of acrylic acid (AA) and a new amphiphilic macromonomer derived from Triton X-100 (MT) were prepared via radical copolymerisation at 60 degrees C, using azobisisobutyronitrile (AIBN) as the initiator and used to formulate conventional glass-ionomer cements with reactive glass fillers. The acid-base reaction was carried out by reacting aqueous solutions of the new copolymer (40 and 50%) with a commercial aluminofluorosilicate glass as used in conventional glass-ionomer cements. The efficacy of the new copolymer in the formation of glass-ionomer cements was investigated and preliminary results on setting parameters, FTIR analysis, mechanical properties and SEM analysis are reported in this paper. RESULTS: The copolymers were synthesized and characterized and further used to successfully prepare glass-ionomer cements. The experimental cements exhibited longer setting and working times in comparison to conventional glass-ionomer cements and the inclusion of tartaric acid enhanced the mechanical properties, which were comparable to the commercial glass-ionomer cement, Fuji IX. SIGNIFICANCE: Glass-ionomer cements prepared using ampiphilic comonomers is expected to influence their behavior in both polar and non-polar environments. As bulky side chains have been incorporated within the polymeric chain it is expected to affect the reaction kinetics of the acid-base reaction.

Study of the influence of beta-radiation on the properties and mineralization of different starch-based biomaterials.

In this work, the effects of beta-radiation are assessed, for the first time, on starch-based biodegradable polymers, with the aim of using it as an alternative sterilization process to the previously studied sterilization methods. Different doses of radiation were used in order to investigate the possibility of using this sterilization technique as a treatment to tailor the surface and bulk properties (namely mechanical) of these polymers. The as-treated substrates were characterized by water-uptake measurements and contact angle (theta) measurements. The mechanical properties of the materials were characterized by tensile tests by means of ultimate tensile strength (UTS) and strain at break (epsilon). The fracture of the surfaces was observed by scanning electron microscopy (SEM). Dynamic mechanical analysis (DMA) was also used to characterize the viscolelastic behavior of the irradiated materials. The main effect of sterilization with beta-radiation over the starch-based polymers seems to be a surface modification by an increase of the hydrophilicity. Nevertheless, because beta-radiation did not significantly affect the mechanical properties, it can be regarded as an effective way of modifying the surface for applications were more hydrophilic surfaces are desirable.

Polymer controlled drug delivery system for growth hormone.

The use of biomaterials as vehicles for pharmacological agents, hormones, and growth factors is at times the best treatment for controlled local administration. Our study was designed to evaluate the in vitro biocompatibility and potential clinical use of a new polymer, hydroxyethyl methacrylate-vinyl pirrolidone. Human fibroblasts were incubated in the presence of the polymer and/or growth hormone, and evaluation was made of both the rate of polymer and hormone degradation and the proliferative effect on the fibroblast population. Results indicate that this polymer is biodegradable and lacks toxicity toward these cells. The hormone was slowly released, as suggested by enhanced cell proliferation.

Random co-polymers based on the poloxamer Bayfit® 10WF15 for biomedical applications.

Random co-polymers were prepared from the poloxamer Bayfit(®) 10WF15 and their thermal and biological properties analyzed. The poloxamer was characterized, functionalized with methacrylate groups (Bayfit-MA) and further co-polymerized with 2-hydroxyethyl methacrylate (HEMA) with Bayfit-MA feed contents of 1, 5 and 10 wt%. Co-polymers were partially soluble in organic solvents and exhibited a single glass transition temperature indicative of a random monomer distribution in the macromolecular chains. In thermogravimetric studies the co-polymers showed two degradation stages, around 210 and 350 °C, respectively. The thermosensitive behaviour of the poloxamer was studied by turbidimetry. Cloud point temperatures of aqueous solutions of Bayfit(®) 10WF15 (0.5-5 wt%) ranged from 15 to 18 °C and for Bayfit(®) 10WF15 methacrylate (0.5-1 wt%) from 6 to 7 °C. DSC thermograms of hydrated co-polymers showed the typical endothermic peaks with phase transition temperatures close to that of physiological medium. The biocompatibility of initial poloxamer and derivatives was analyzed with human fibroblasts cultures. The IC(50) value of Bayfit(®) 10WF15 was 1.4 mg/ml. Cellular extracts of the co-polymers were not cytotoxic and cellular proliferation and DNA content depended on co-polymer composition.

Selective biological response of human pulmonary microvascular endothelial cells and human pulmonary artery smooth muscle cells on cold-plasma-modified polyester vascular prostheses.

The aim of this work was to improve the hemocompatibility and the selectivity according to cells of non-woven poly(ethylene terephthalate) (PET) membranes. Non-woven PET membranes were modified by a combined plasma-chemical process. The surface of these materials was pre-activated by cold-plasma treatment and poly(acrylic acid) (PAA) was grafted by the in situ free radical polymerization of acrylic acid (AA). The extent of this reaction and the number of carboxylic groups incorporated were evaluated by colorimetric titration using toluidine blue O. All samples were characterized by SEM, AFM and thermogravimetric analysis, and the mechanical properties of the PAA grafted sample were determined. A selective cell response was observed when human pulmonary artery smooth muscle cells (HPASMC) or human pulmonary micro vascular endothelial cells (HPMEC) were seeded on the modified surfaces. HPASMC proliferation decreased about 60%, while HPMEC proliferation was just reduced about 10%. PAA grafted samples did not present hemolytic activity and the platelet adhesion decreased about 28% on PAA grafted surfaces.

A study on partially biodegradable microparticles as carriers of active glycolipids.

This paper describes a study on the preparation and characterisation of partially biodegradable microparticles of poly(epsilon-caprolactone)/poly(ethyl methacrylate) (PCL/PEMA) as carriers of synthetic glycolipids with antimitotic activity against brain tumour cells. Microparticles prepared by suspension polymerisation of methacrylate in the presence of already polymerised PCL showed a predominantly spherical but complex morphology, with segregation of PCL micro/nano-domains towards the surface. Small diameter discs were prepared by compression moulding of blends of microparticles and the active principle under mild conditions. The in vitro behaviour of the discs and release of the glycolipid were studied in different simulated fluid models. Ingress of fluids increased with increasing hydrophobicity of the medium. Release of the glycolipid was sustained in all fluids, the most prolonged profile being in human synovial fluid and phosphate-buffered saline modified with 20 vol.% dioxane. Slow disintegration of the discs and partial degradation of the microparticles was evident in accelerated studies. The antimitotic activity of glycolipid released from the discs was proved against a human glioblastoma line. This activity, along with selectivity against human fibroblasts, could be controlled by the amount of drug charged in the disc.

Synthesis of HMDI-based segmented polyurethanes and their use in the manufacture of elastomeric composites for cardiovascular applications.

For short-term cardiovascular application, segmented polyurethanes (SPUs) based on 4,4-methylenebis(cyclohexyl isocyanate) (HMDI), polytetramethylenglycol (PTMG) and 1,4-butanediol (BD) were synthesized and characterized by spectroscopy (FT-IR, (1)H-NMR) and thermal (TGA, DMA, DSC) and mechanical techniques. The segmented nature of the SPUs was not easily established by spectroscopic means; however, TGA allowed the quantification of the rigid segments content by the significant mass loss between 348 and 356 degrees C. The alpha transition was detected by DMA and related to the T(g) of the soft segments at -50 degrees C, while DSC showed the presence of an endothermic transition above 80 degrees C attributed to the melting of rigid segments. Two types of composites were prepared using the synthesized SPUs and Lycra (either T162B or T162C). The first one consisted of a two layers casting laminated while the second one was a classic unidirectional fibre-reinforced material. Laminate composites prepared with SPU containing 23.9% and 33.9% of rigid segments and Lycra T162C exhibited a higher tensile modulus but lower tensile strength than composites prepared with Tecoflex SG-80A (39.7% of rigid segments). The energy of adhesion between layers on these composites ranged from 475 to 2150 J. Fibre-reinforced SPUs exhibited higher moduli than the two layer laminated composites with increasing amounts of rigid segments in the matrix and by increasing Lycra T162C content (up to 10%). This behaviour was explained by SEM, which showed a good fibre-matrix bonding.