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Biomedical subjects

J San Román

Publications and source records attributed to J San Román.

At least 19 recordsLinked to original sources
PubMed2007

Biological response of new activated acrylic bone cements with antiseptic properties. Histomorphometric analysis.

The biological response to an acrylic bone cement cured with 4,4'-bis-dimethylamino benzydrol (BZN) as activator of reduced cytotoxicity and antiseptic properties, has been carried out and compared with that obtained for CMW 3 cement. Histomorphometrical data (undecalcified trichromic Goldner staining) were obtained by measuring the most significant variables at the bone-cement interface. Quantitative results of tissue response revealed that newly formed bone and connective tissue were maximum at 4 weeks whereas bone marrow increased with time of implantation for both cements. Statistical analysis (p < 0.05) showed no significant differences in newly formed bone and bone marrow with time and between both groups, however, connective tissue significantly decreased between 4 weeks and 12 weeks for BZN cement, and between 12 weeks and 24 weeks for CMW3. By comparing both cements at each time, lower significant percentage of connective tissue at the bone-cement interface of the BZN cement, was obtained at 12 and 24 weeks, however, a very low amount of connective tissue was found for both cements. All the results indicate that the new activated system could be applied clinically in a relatively short time, after the corresponding preclinical study.

Animals↗
PubMed2006

[Predictive biochemical indicators of a postlaryngectomy pharyngocutaneous fistula: a clinical study].

UNLABELLED: The aim of this clinical study was to determinate biochemical predictor indicators of postlaryngectomy pharyngocutaneous fistula. PATIENTS AND METHODS: We have studied 100 patients with T2- 4 a laryngeal and piryform sinus carcinoma who underwent a laryngectomy. All patients were ASA 2-3. We studied serum albumin, protein serum level, cholesterol and lymphocites in each patient. These variables underwent statistical analysis (p < 0.05). RESULTS: 19% of the patients developed a postlaryngectomy pharyngocutaneous fistula, with a long-stay of 25 days vs. 10 days of stay in patients without postlaryngectomy pharyngocutaneous fistula. 7 postlaryngectomy pharyngocutaneous fistula needed surgical repair. Low serum albumin (< 3.5 g/dL) and a low level of serum proteins (< 6.5 g/dL) were predictive indicators of postlaryngectomy pharyngocutaneous fistula (p < 0.05). CONCLUSIONS: Our results suggest that a low-level of serum proteins and albumin are predictive clinical parameters of postlaryngeal pharyngocutaneous fistula.

Biomarkers↗
PubMed2005

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.

Acrylates↗
PubMed2005

Observation of spontaneous self-channeling of light in air below the collapse threshold.

We report the observation of the self-guided propagation of 120 fs, 0.56 mJ infrared radiation in air for distances greater than 1 m. In contrast with the known case of filamentation, in the present experiment the laser power is lower than the collapse threshold. Therefore the counterbalance between Kerr self-focusing and ionization induced defocusing as the stabilizing mechanism is ruled out. Instead, we find evidence of a process in which the transversal beam distribution reshapes into a form similar to a Townes soliton, with the particularity of a very high stability. We include numerical support for this conclusion.

Journal Article↗
PubMed2005

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.

Beta Particles↗
PubMed2005

Histological evaluation of scar tissue inflammatory response: the role of hGH in diabetic rats.

This paper describes a polymer site-specific delivery system containing human growth hormone in an in vivo model of scarring in the diabetic state. Copolymer discs with the hormone were introduced into incisions made in rats previously injected with streptozotocin in order to induce diabetes. Tissue specimens for evaluation were obtained at 3, 7 or 10 days after the procedure. Study groups were healthy rats and diabetic rats untreated or treated with/without the hormone. Histological sections were prepared for light microscopy examination of wound zones. Three and 7 days after surgery, polymer remains could be observed in the subcutaneous tissue. These remnants induced a moderate foreign body reaction. The number of macrophages detected was directly related to neovessel formation and metalloelastase expression. The CD4+/CD8+ ratio was low during the initial follow up stages (3 and 7 days) in untreated diabetic rats, yet an increased ratio corresponding to areas around the polymer remains was noted in the animals treated with copolymer loaded with the growth hormone. Copolymer is biodegradable in vivo and may be used as a vehicle for the slow release of active substances. The presence of the hormone at the site of skin injury induces cell proliferation and enhances the repair process.

Animals↗
PubMed2004

Influence of cross-linked PMMA beads on the mechanical behavior of self-curing acrylic cements.

Cross-linked PMMA beads were prepared with the use of two cross-linking agents with different chain lengths: triethylene glycol dimethacrylate (TEGDMA) and poly(ethylene glycol) dimethacrylate (PEGDMA). Beads containing 10 wt % TEGDMA and 2, 5, and 10 wt % PEGDMA were synthesized by suspension polymerization. Experimental cement formulations were prepared by replacing part of the PMMA powder phase by an equivalent weight of the cross-linked beads. The mechanical behavior of the modified cements was carried out by testing the cements in flexure and compression. All cements displayed a higher flexural modulus, which was accompanied with a slight decrease in the flexural strength. The two-parameter Weibull model, which was used to analyze the flexural strength data, gave a good representation of the fracture load distribution. In cements prepared with beads containing 2 and 5 wt % PEGDMA and 10 wt % TEGDMA, no improvement in the flexural strength was observed. Debonding of the particles from the matrix was considered responsible for the decreased flexural strength. On the contrary, cements prepared with different proportions of beads containing 10 wt % PEGDMA resulted in a markedly increased flexural strength compared with the unmodified cement. An improved reinforcing effect of the cross-linked beads and a significant degree of bonding with the matrix in these cements account for the superior flexural strength compared with the other composite cements tested.

Acrylates↗
PubMed2004

Mechanical characterization of self-curing acrylic cements formulated with poly(methylmethacrylate)/poly(epsilon-caprolactone) beads.

New acrylic-based cements were formulated by replacing a mass fraction of 20% of poly(methyl methacrylate) (PMMA) powder by PMMA/poly(epsilon-caprolactone) (PCL) beads (throughout this article all compositions are given as mass fractions, unless specified otherwise). PMMA/PCL beads containing 10 and 30% PCL were synthesized by suspension polymerization. Cements were prepared by replacing part of the PMMA powder of the formulation by an equivalent mass of PMMA/PCL particles. The influence of the PCL content in the beads on the mechanical behavior was assessed by testing the cements in flexure and compression. The addition of PMMA/PCL particles with 10% PCL content resulted in a marked increase in both flexural modulus and flexural strength related to the plain PMMA beads formulation. This improvement was attributed to a decrease in the cured material porosity. Conversely, by the incorporation of beads with 30% PCL content the flexural properties decreased. This behavior was attributed to the debonding of the particles from the matrix, which was revealed by SEM images. The observed compressive yield strength decrease with the increase of PCL content in the beads was attributed to a low degree of adhesion between the heterogeneous particles and the matrix as well as to the plasticizing effect of the PCL.

Bone Cements↗
PubMed2004

Capillary electrophoresis-mass spectrometry of basic proteins using a new physically adsorbed polymer coating. Some applications in food analysis.

A new physically adsorbed capillary coating for capillary electrophoresis-mass spectrometry (CE-MS) of basic proteins is presented, which is easily obtained by flushing the capillary with a polymer aqueous solution for two min. This coating significantly reduces the electrostatic adsorption of a group of basic proteins (i.e., cytochrome c, lysozyme, and ribonuclease A) onto the capillary wall allowing their analysis by CE-MS. The coating protocol is compatible with electrospray inonization (ESI)-MS via the reproducible separation of the standard basic proteins (%RSD values (n = 5) < 1% for analysis time reproducibility and < 5% for peak heights, measured from the total ion electropherograms (TIEs) within the same day). The LODs determined using cytochrome c with total ion current and extracted ion current defection were 24.5 and 2.9 fmol, respectively. Using this new coating lysozymes from chicken and turkey egg white could be easily distinguished by CE-MS, demonstrating the usefulness of this method to differentiate animal species. Even after sterilization at 120 degrees C for 30 min, lysozyme could be detected, as well as in wines at concentrations much lower than the limit marked by the EC Commission Regulation. Adulteration of minced meat with 5% of egg-white could also be analysed by our CE-MS protocol.

Adsorption↗
PubMed2004

Injectable self-curing bioactive acrylic-glass composites charged with specific anti-inflammatory/analgesic agent.

Injectable bioactive acrylic formulations based on poly(methyl methacrylate) (PMMA) and different amounts of bioactive glasses in the system SiO2-CaO-Na2O-P2O5 have been prepared in the presence of the anti-inflammatory analgesic drug fosfosal, the sodium salt of 2-phosphonoxibenzoic acid, to be used in minimally invasive surgery. The injectability of the formulations evaluated according to the established protocol was around 80%. The experimental formulations provided maximum temperatures in the range 50-60 degrees C, which were lower than those of commercial acrylic bone cements currently used in percutaneous vertebroplasty (PVP). Residual monomer content of any formulation was inferior to 5%. Compressive yield strength of dry specimens was in the range 80-95 MPa, but it decreased after immersion in SBF to values in the range 30-50 MPa, due to the dissolution of the bioactive glasses and the drug in the medium. The release of fosfosal was evaluated in vitro (pH = 7.0). The release profile against time obtained from a PMMA cement was quasi-linear and the 80% of the initial amount of drug was released in 175 h. However, for bioactive cements, the 80-100% of the fosfosal charged was released in approximately 48 h, due to the dissolution of the glasses in the medium. Values of weight loss of the cements determined gravimetrically ranged between 16% and 26% depending on the initial amount of fosfosal, i.e. 20 or 30 wt%, respectively. The weight loss and the water uptake were simultaneous processes, and values of hydration degree were around 10-14%. The formation of an apatite-like layer was detected on the surface of the cements at different periods of time depending on the composition of the bioactive glasses. The cements containing the glasses with P2O5 produced the growth of the apatite layer in shorter periods of time. The presence of fosfosal accelerated the precipitation of this layer independently on the glasses. The in vivo biocompatibility studied by intramuscular implantation in rats showed the absence of an anti-inflammatory response and a fibrous layer around the implant for the cement prepared with PMMA/fosfosal which is attributed to the therapeutic action of fosfosal acting in situ. The response to cements prepared with bioactive glasses and fosfosal showed a mild inflammatory reaction with the formation of the typical fibrous capsule around the implanted material.

Analgesics↗
PubMed2004

Influence of beta-radiation sterilisation in properties of new chitosan/soybean protein isolate membranes for guided bone regeneration.

Novel chitosan (cts) and soybean protein isolate (SI) blended membranes were prepared. These membranes were produced by solvent casting. Besides combining the advantages of both materials, cts/SI membranes exhibit a biphasic structure that will eventually originate in situ porous formation, through a two-step degradation mechanism. In this particular work the effect of beta-radiation over the properties of these membranes was evaluated. beta-radiation sterilisation was performed at three different doses (25, 50 and 100 kGy) and eventual surface chemical changes were evaluated by Fourier transformed infrared--with attenuated total reflection and contact angle measurements. Moreover, eventual bulk properties changes due to beta-radiation were assessed by means of mechanical tensile tests and water uptake measurements. In general, no substantial changes were detected on the studied properties, with the exception of the surface energy that was found to be slightly increased for higher applied doses.

Beta Particles↗
PubMed2003

Biocompatibility and other properties of acrylic bone cements prepared with antiseptic activators.

Acrylic bone cements prepared with activators of reduced toxicity have been formulated with the aim of improving the biocompatibility of the final material. The activators used were N,N-dimethylaminobenzyl alcohol (DMOH) and 4,4'-dimethylamino benzydrol (BZN). The toxicity, cytotoxicity, and antiseptic action of these activators were first studied. DMOH and BZN presented LD50 values 3-4 times higher than DMT, were less cytotoxic against polymorphonuclear leucocytes, and possessed an antimicrobial character, with a high activity against the most representative microorganisms involved in postoperative infections. The properties of the acrylic bone cements formulated with DMOH and BZN were evaluated to determine the influence of these activators on the curing process and the physicochemical characteristics of the cements. A decrease of the peak temperature was observed for the curing with DMOH or BZN with respect to that of one commercially available formulation (CMW 3). However, residual monomer content and mechanical properties in tension and compression were comparable to those of CMW 3. The biocompatibility of acrylic bone cements containing DMOH or BZN was studied and compared with CMW 3. To that end, intramuscular and intraosseous implantation procedures were carried out and the results were obtained from the histological analysis of the surrounding tissues at different periods of time. Implantation of rods of cement into the dorsal muscle of rats showed the presence of a membrane of connective tissue, which increased in collagen fibers with time of implantation, for all formulations. The intraosseous implantation of the cements in the dough state in the femur of rabbits, revealed a higher and early osseous neoformation, with the presence of osteoid material surrounding the rest of the cured material, for the cement prepared with the activator BZN in comparison with that obtained following the implantation of the cement cured with DMOH or DMT (CMW 3).

Alcohols↗
PubMed2003

Elimination of barium sulphate from acrylic bone cements. Use of two iodine-containing monomers.

The aim of this work is to present a new approach to joint arthroplasty failure related to bone cement mantle. As barium sulphate is considered one of the main causes of mechanical weakness in the cement, we substituted this inorganic radiopacifier of the solid component for radiopaque monomers in the liquid component. We obtained two different cements, one containing 5 vol% 2-[2',3',5'-triiodobenzoyl] ethyl methacrylate (TIBMA) and the other containing 3,5-diiodine salicylic methacrylate (DISMA). In both cases, the mechanical properties of these new cements were better than those of the barium sulphate-containing cement. The radiopacity obtained was comparable to that of the aforementioned cement and all the samples showed good biocompatibility.

Barium Sulfate↗
PubMed2003

A novel controlled drug-delivery system for growth hormone applied to healing skin wounds in diabetic rats.

Controlled release systems for drugs, hormones and growth factors can be particularly useful in tissue repair processes. These systems act as a biodegradable support containing the substance to be delivered, allowing their gradual release. In the past years, the local application of growth factors has acquired special relevance as a therapeutic option for use in subjects who show deficient tissue scarring, the hormone dose being the limiting factor for its success. In this study, the in vitro biocompatibility of a copolymer formed by vinylpyrrolidone and 2-hydroxyethyl methacrylate, used as an administration vehicle for hGH, was evaluated. The system was then tested in vivo in terms of its capacity for healing incisional wounds in healthy and diabetic rats. For the in vitro studies, polymer and hormone degradation rates were determined, and polymer biocompatibility was evaluated in fibroblast cultures. In the in vivo experiments, an incision was made in the back of the animals, and polymers discs with/without hGH, were introduced in the aperture. Morphological, immunohistochemical and morphometric evaluations were performed on wound tissue specimens 3-10 days after surgery. In vitro, the polymer was found to be biodegradable and showed no toxic effects on fibroblasts, the hormone being slowly released to the culture medium. In untreated diabetic rats, a delayed skin scarring and cell response were observed, compared to that noted in healthy animals. Skin closure, keratinisation and fibrosis occurred earlier in the presence of the polymer-hGH system. The use of this co-polymer as an administration vehicle for hGH improves the wound scarring process in the pathological setting of diabetes.

Animals↗
PubMed2002

New acrylic bone cements conjugated to vitamin E: curing parameters, properties, and biocompatibility.

Acrylic bone cement formulations with antioxidant character were prepared by incorporation of a methacrylic monomer derived from vitamin E (MVE). Increasing concentrations of this monomer provided decreasing peak temperature values, ranging from 62 to 36 degrees C, and increasing setting time with values between 17 and 25 min. Mechanical properties were evaluated by compression and tension tests. Compressive strength of the new formulations were superior to 70 MPa in all cases. The cement containing 25 wt % MVE, however, showed a significant decrease in tensile properties. Biocompatibility of the new formulations was studied in vitro. The analysis of the effect of leachables from cements into the media showed continued cell proliferation and cell viability with a significant increase for the cement containing 15 wt % MVE. This formulation also showed a significant increase in cellular proliferation over a period of 7 days as indicated by the Alamar Blue test. The cells were able to differentiate and express phenotypical markers in presence of all materials. A significant increase in alkaline phosphatase activity was observed on the cements prepared in presence of 15-25 wt % MVE compared with PMMA. Morphological assessment showed that the human osteoblast (HOB) cells were able to adhere, retain their morphology, and proliferate on all the cements.

Acrylates↗
PubMed2002

Starch-based biodegradable hydrogels with potential biomedical applications as drug delivery systems.

The design and preparation of novel biodegradable hydrogels developed by the free radical polymerization of acrylamide and acrylic acid, and some formulations with bis-acrylamide, in the presence of a corn starch/ethylene-co-vinyl alcohol copolymer blend (SEVA-C), is reported. The redox system benzoyl peroxide (BPO) and 4-dimethylaminobenzyl alcohol (DMOH) initiated the polymerization at room temperature. Xerogels were characterized by 1H NMR and FTIR spectroscopies. Swelling studies were performed as a function of pH in different buffer solutions determining the water-transport mechanism that governs the swelling behaviour. Degradation studies of the hydrogels were performed in simulated physiological solutions for time up to 90 days, determining the respective weight loss, and analyzing the solution residue by 1H NMR. The mechanical properties of the xerogels were characterized by tensile and compressive tests, as well as by dynamo-mechanical analysis (DMA). Dynamo-mechanical parameters are also reported for hydrated samples.

Aniline Compounds↗
PubMed2002

Monitoring ibuprofen enantiomers released from polymeric systems.

Two methacrylic derivatives of ibuprofen (N-[4-[2-(4-isobutylphenyl)propionyloxy]phenyl] methacrylamide (MAI) and 2-[(4-isobutylphenyl)propionyloxy]ethyl methacrylate (MEI)) were used together with 2-hydroxyethyl methacrylate (HEMA) to synthesize four polymeric materials: two hydrophobic homopolymers, PMAI and PMEI, and two hydrophilic copolymers containing 70% (w/w) HEMA, MAI-HEMA 30 and MEI-HEMA 30. The enantiomeric determination of R- and S-IBU released from these four systems has been carried out by capillary electrophoresis. Release of R- and S-IBU was monitored during in vitro assays done at 37 degrees C at pH 7.4 and 10 in buffered solutions and rat plasma. There is a hydrolytical activation in plasma and at pH 10 compared to pH 7.4; moreover, the release rate from the copolymers is much higher than from the homopolymers as a consequence of the greater hydrophilic character. A slight excess of the S-enantiomer of IBU is observed in all the experiments, being more relevant at higher release rates, i.e. copolymers at pH 10.

Animals↗