Synthesis and Characterization of Novel Radiopaque Polycarbonate.

Polymeric materials implanted in the human body are usually invisible under X-ray, and the mixing of heavy metal salts into polymeric materials by physical compounding often poses compatibility problems. A new iodine-containing cyclic carbonate monomer, 4-iodo-N-(2-oxo-1,3-dioxan-5-yl)benzamide (IBTMC), is synthesized, which has a degradable carbonate group as its basic structural unit and iodine atoms attached to the side chain in the form of covalent bonds. The ring-opening polymerization of IBTMC is achieved at room temperature under the catalysis of the solid superbase 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD). The structure and X-ray developing ability of the synthesized polycarbonate are characterized by 1 H-NMR, X-ray photoelectron spectroscopy (XPS), energy dispersive X-ray spectroscopy (EDS), Gel Permeation Chromatography (GPC), and micro-computed tomography (Micro-CT). The iodine atoms remain bound to the polymer as covalent bonds after a series of reactions and exhibit a high level of X-ray opacity. In vitro degradation experiments of the polymer prove that the polymer is degradable.

Preparation and drug-delivery potential of metronidazole-loaded PELA tri-block co-polymeric electrospun membranes.

The aim of this study was to investigate the potential of poly(ethylene glycol-co-lactide) (PELA tri-block with a segmental sequence of PLA-PEG-PLA) electrospun membranes as drug-delivery vehicles using metronidazole as a model drug. PELA membranes with smooth surfaces and no bead defects were electrospun from polymer solutions containing 20% (w/v) PELA in 8:2 N,N-dimethyl formamide (DMF)/acetone. The morphology of the drug-loaded electrospun membranes was influenced by electrospinning parameters such as the flow rate and voltages during preparation. Metronidazole could be released from the electrospun membranes and was characterized by an initial burst effect. Higher voltages led to faster release rates, while an increase in the flow rate decreased the drug release. The incorporation of metronidazole into the electrospun membranes decreased their surface hydrophilicity. The amount of drug released from the electrospun membranes was effective in inhibiting microbial growth. Cell adhesion on the PELA membranes with or without drug was less than that on the homo-polymeric PDLLA membranes. Proliferation of L929 mouse fibroblasts on the PELA membranes was observed. This study confirms the potential of metronidazole-loaded PELA biodegradable electrospun membranes for optimizing the clinical therapy of post-surgical adhesions and infections.

Tissue anti-adhesion potential of biodegradable PELA electrospun membranes.

The most commonly used anti-adhesion device for separation and isolation of wounded tissues after surgery is the polymeric membrane. In this study, a new anti-adhesion membrane from polylactide-polyethylene glycol tri-block copolymer (PELA) has been synthesized. The synthesized copolymers were characterized by gel permeation chromatography and (1)H nuclear magnetic resonance spectroscopy. PELA membrane was prepared by electrospun. The prepared copolymer membranes were more flexible than the control poly-d-l-lactic acid (PDLLA) membrane, as investigated by the measurements of glass transition temperature. Its biocompatibility and anti-adhesion capabilities were also evaluated. In vitro cell adhesions on the PELA copolymer membrane and PDLLA membrane were compared by the culture of mouse fibroblasts L929 on the surfaces. For in vivo evaluation of tissue anti-adhesion potential, the PDLLA and PELA copolymer membranes were implanted between cecum and peritoneal wall defects of rats and their tissue adhesion extents were compared. It was observed that the PELA copolymer membrane was very effective in preventing cell or tissue adhesion on the membrane surface, probably owing to the effects of hydrophilic polyethylene glycol.

Preparation and characterization of biodegradable poly(D,L-lactide) and surface-modified bioactive glass composites as bone repair materials.

In order to improve filler dispersion and phase compatibility between poly(D,L-lactide) (PDLLA) and inorganic bioactive glass (BG) particles, and to enhance the mechanical properties of PDLLA/BG composites, the silane coupling agent 3-glycidoxypropyltrimethoxysilane (KH570) was used to modify the surface of BG particles (represented by KBG). The structure and properties of PDLLA/BG and PDLLA/KBG composites were investigated by mechanical property testing and scanning electron microscopy (SEM). This study demonstrated that the Guth and Gold models can be combined to predict the Young's modulus of the composites. The Pukanszky modulus showed that the interaction parameter B of PDLLA/KBG composites was higher than that of the PDLLA/BG, which indicates that there is a higher interfacial interaction between the PDLLA and KBG. The composites were incubated in simulated body fluid (SBF) at 37 degrees C to study the in vitro degradation and bioactivity of the composites and to detect bone-like apatite formation on their surfaces.

An ionically crosslinked hydrogel containing vancomycin coating on a porous scaffold for drug delivery and cell culture.

The aim of this study was to prepare and characterize a scaffold with an ionically crosslinked hydrogel coating layer containing a water-soluble drug, vancomycin, via a novel drug loading method for sustained drug delivery and surface modification. The poly(D,L-lactide acid) (PDLLA)/biphasic calcium phosphate (BCP) scaffold with a highly inter-connected porous structure was fabricated by a particle-leaching/thermally induced phase separation (TIPS) method. The pre-vacuumized scaffold was immersed into an alginate/vancomycin solution. Following impregnation by the solution, the scaffold was removed and immersed in a CaCl(2) solution for 30 min to allow gelation of the alginate solution. In this way, the drug was not exposed to organic solvents or detrimental temperature conditions and it could avoid loss of drug during the leaching process. The water contact angles of the scaffold surface decreased after being coated with the hydrogel. The in vitro drug release profile showed sustained release properties which were influenced by the alginate concentration and the dissolution medium. A standardized bacterial assay showed that the drug was still active after association with the scaffold by this gentle method of drug loading. The in vitro osteoblast culture experiments confirmed the biocompatibility of the scaffold for attachment and proliferation of osteoblasts.

Fabrication and characterization of hydrophilic electrospun membranes made from the block copolymer of poly(ethylene glycol-co-lactide).

To improve the hydrophilicity, pliability, and egradability of some biodegradable polymers such as polylactide (PLA), a triblock copolymer, and poly(ethylene glycol-co-lactide) (PELA) has been electrospun into fibrous membranes in the fiber sizes of 7.5 microm to 250 nm. The relationship between electrospinning parameters (such as voltage, concentration, and feeding rate) and the fiber diameters has been investigated. The characterizations for the structure and morphology of electrospun membranes were carried out using differential scanning calorimetry (DSC), (1)H NMR, and scanning electron microscopy (SEM). The hydrophilicity of the membrane was determined by contact angle measurements in bi-distilled water, and it was shown that the hydrophilicity of the copolymer could be adjusted by the content of the poly (ethylene glycol) (PEG) segment in the copolymer. The results of in vitro degradation study showed that the submicrostructure of the fibrous membrane and the incorporation of hydrophilic PEG into PLA block could accelerate the degradation of the membrane in regards to the changes of inherent viscosity, tensile strength, and weight loss.

[Effects of astragalus polysaccharides-chitosan/polylactic acid composite material on biological behavior of canine bone marrow stromal cells cultured in vitro].

OBJECTIVE: To observe the biological behavior of canine bone marrow stromal cells (BMSCs) cultured in vitro with the astragalus polysaccharides-chitosan/polylactic acid (AP-C/PLA) and with the chitosan/polylactic acid (C/PLA) and to find a suitable compound material for periodontal tissue engineering. METHODS: BMSCs (induced 14 days by 50 mg/L vitamine C, 10(-8) mol/L dexamethasone, 10 mmol/L beta-sodium glycerylphosphate) were cultured on AP-C/PLA or C/PLA for 5 days respectively. The BMSCs attachment and the morphology were observed with scanning electronic microscope and the combining rates were counted. Type I collagen synthesis was examined with immunohistochemistry staining and the content of osteocalin was determined with radio-immunological method. RESULTS: Combining rates, type I collagen synthesis, and the content of osteocalin of BMSCs on AP-C/PLA were significantly higher than those on C/PLA. CONCLUSION: AP-C/PLA may promote the BMSC proliferation, differentiation and extracellular matrix synthesis, and it can be used as a good scaffold material for bone tissue engineering.

Novel polyelectrolyte carboxymethyl konjac glucomannan-chitosan nanoparticles for drug delivery. I. Physicochemical characterization of the carboxymethyl konjac glucomannan-chitosan nanoparticles.

Carboxymethyl konjac glucomannan-chitosan (CKGM-CS) nanoparticles, which are well dispersed and stable in aqueous solution, were spontaneously prepared under very mild conditions via polyelectrolyte complexation. The physicochemical properties of the nanoparticles were identified by Zetasizer 3000 and Fourier transform infrared. It was found that at various CKGM and CS concentrations the particles ranged in size from approximately 50 to 1200 nm, and the zeta potential from 15 to 45 mV. By changing pH value of the medium and increasing the concentration of salt, the mean size of the particles increased and the zeta potential decreased. Also, investigations on the encapsulation efficiency of the bovine serum albumin loaded CKGM-CS nanoparticles were also undertaken. This nanoparticulate system driven by complex formation shows potential as an advanced drug delivery system for water-soluble drugs.

Novel polyelectrolyte carboxymethyl konjac glucomannan-chitosan nanoparticles for drug delivery. II. Release of albumin in vitro.

Carboxymethyl konjac glucomannan-chitosan (CKGM-CS) nanoparticles were spontaneously prepared under very mild conditions via polyelectrolyte complexation. Bovine serum albumin (BSA), as a model protein drug, was incorporated into the CKGM-CS nanoparticles. The physicochemical properties of the BSA-loaded nanoparticles were identified by Zetasizer 3000 and FTIR spectrophotometry. Their sizes were from 330 nm to 900 nm; zeta potentials were positive according to varies CKGM/CS ratios. The encapsulation efficiency was up 20%. The release behavior in vitro of BSA from the nanoparticles was also investigated. We could find that the BSA release from the CKGM-CS nanoparticles is much more influenced by the CS coating layer than by the CKGM inner structure. And the CKGM-CS matrices not only exhibited pH-responsive properties, but ionic strength-sensitive properties. These systems may present a potential for pulsatile protein drug delivery.

[Study on chronic toxicity to rats of implantation of super-high molecular weight polylactate].

OBJECTIVE: To make sure whether super-high molecular weight polylactate is toxic to the body after it has been implanted into the body for a long period. METHODS: We implanted super-high molecular weight polylactate into the rats and took the specimens of blood at 3, 6, 9, 12 months after the operation. The changes of proteins, electrolyte, enzyme and other indices were observed. At the same time, the tissue around the implants were taken out to carry out the histological observation. RESULTS: At 3, 6, 9, 12 months after the operation, the levels of albumin, globulin, total bilirubin, direct bilirubin, triglyceride, glucose, K+, Na+, Cl-, Ca2+, alkaline phosphatase, glutamic-pyruvic transaminase in the blood plasma were all in the normal range; there were no significant differences between the experimental group and the control group. The level of lactate dehydrogenase increased slightly, but there was no statistically significant difference between the experimental group and the control group. There were no non-reversible immune rejection around the implants in the histological observation. CONCLUSION: Super-high molecular weight polylactate is not toxic to the body after it has been implanted into the animals for a long period.

[Repair of hard cleft palate with absorbable membranes made by poly-DL-lactic acid: a feasibility study].

OBJECTIVE: To investigate the feasibility and clinical results of applying poly-DL-lactic acid (PDLLA) biomembranes in cleft palate repair. METHODS: 68 cleft palate patients were divided into study group and control group. The traditional surgical method was used to control group to close the soft cleft palate, and the PDLLA biomembrane was used to study group and implanted into the surgical gap between the periosteum and bone at the hard palate, and fixed with suture. The duration, blood loss at operation, post-operative complication, wound healing and recovery were recorded and compared to conventional cleft palate repair. RESULTS: Operations were successfully completed on all 34 patients. Wound healing of soft palate and uvula was uneventful with no incidence of fistula or dehiscence. The primary healing on tissue defect of hard palate occurred in 29 patients, secondary healing occurred in 3 patients, permanent fistula between the oral cavity and the nasal cavity occurred in only one patients, and 3 patients left over fistula on alveolar process. Compared to traditional cleft palate repair, blood loss and incidence of fistula on alveolar process were decreased; the average surgical time was 89.25 minutes and was not prolonged; and there was no significant increase in post-operative complication. CONCLUSION: Hard cleft palate repair with PDLLA biomembranes is safe, simple and practical with good clinical results and is beneficial to minimize the bad influences towards the development and growth for maxilla of cleft palate patients.

[Influence of super high molecular weight poly D,L-lactic acid on viability and new bone formation of osteoblasts].

OBJECTIVE: To investigate the influence of the viability and new bone formation of osteoblasts by the super high molecular weight poly D,L-lactic acid (SHMW-PDLLA). METHODS: 1. The osteoblasts derived from neonatal rat were grown and maintained at steep of SHMW-PDLLA and normal culture medium. The viability and function of the osteoblasts were measured with MTT array. 2. The plate and screws made of SHMW-PDLLA were implanted and fixed at the artificial fractured mandible of dogs. Specimens were gained at 3 and 6 months and examined with macroscopy and SEM. RESULTS: 1. There is no significant difference of OD values between the experimental group and the control group (P > 0.05). The SHMW-PDLLA isn't toxic to osteoblast at 1 week and 2 weeks, and the toxicity is 3% at 3 days. 2. There were a lot of new bone formed between the implanted SHMW-PDLLA plate and bone tissues under SEM. CONCLUSION: SHMW-PDLLA hasn't pathological influence on the viability and new bone formation of osteoblasts and it is feasible in tissue engineering of bone.