Hydrogel Foam Research Articles

Better bone patching with hydrogel foam

Biomaterials![Figure][1] Pore structure of a 3D architectured hydrogel (ArcGel) CREDIT: HZG 2015 Bone grafts are currently the clinical standard for replacing larger bone defects caused by trauma, infections, or tumors. Degradable biomaterials are not sufficient for regenerating bone without the addition of peptides or growth factors to attract and direct the needed cells. Neffe et al. devised a one-step process for creating hydrogels through a foaming process using gelatin and lysine connected by urea junctions. The gels form an open porous structure that allows cells to invade and provides support for their adhesion, as well as offering tailorable local environments and mechanical properties and controlled and rapid degradation. In vivo testing for the regeneration of 5-mm femoral defects in rats showed healing capacity comparable to that of bone grafts after 6 weeks. Adv. Mater. 10.1002/adma.201404787 (2015). [1]: pending:yes

Use of transpleural hydrogel foam plugs for reducing pneumothorax complicating CT-guided chest biopsy

Purpose: CT chest biopsy is a proven diagnostic technique, but is commonly complicated by pneumothorax. We evaluated the effectiveness of trans- pleural hydrogel foam plugs to reduce post-biopsy pneumothorax.

Post-expansile hydrogel foam aerosol of PG-liposomes: A novel delivery system for vaginal drug delivery applications

The purpose of this work was to develop and characterize a novel delivery system of post-expansile hydrogel foam aerosol of propylene glycol-embodying liposomes (PG-liposomes) (PEHFL) for vaginal drug delivery applications. Matrine (MT) was used as a model drug to investigate the vaginal mucous membrane permeation behavior of MT from PEHFL versus PG-liposomes foam aerosol (PLFA), hydrogel foam aerosol (HFA) and hydrogel (HYG). The MT loaded PG-liposomes were characterized for shape, particle size, polydispersity, zeta potential and encapsulation efficiency; the foams of PEHFL were also characterized for swelling behavior, mucoadhesive force and duration.Results revealed that: (i) the MT loaded PG-liposomes had a mean size of 122±16nm, a good polydispersity index of 0.147±0.023, and exhibited a negative charge of −47.5±0.4mV, the MT entrapment capacity in PG-liposomes (was calculated as percentages of total drug) was 80.8±2.6%; (ii) the foams of PEHFL had a laggingly swelling process after spurted from a sealed container, and the higher the temperature of the surrounding environment, the greater the degree of swelling, this swelling state of foams would greatly enhance drug spread uniformly in vaginal canal and contact the vaginal walls tightly; (iii) the foams of PEHFL had a mucoadhesive force about 1460±123mN/cm2, and could sustain 85±11min in vitro; (iv) the overall mean permeated MT through unit mass of porcine vaginal tissue from PEHFL was 2.64, 2.34 and 7.59 times higher than that from PLFA, HFA and HYG, respectively (t-test, P<0.05); and the quantity of MT remaining in the vaginal tissue at the end of the 12h experiment was also significantly greater (t-test, P<0.05) from the PEHFL than from PLFA, HFA and HYG. All of these results indicate that the main advantages of PEHFL over conventional dosage forms are the ability to enhance the vaginal mucosa permeability of MT, spread uniformly in vaginal canal especially the highly folded epithelial surfaces, prolong the residence time at the site of administration and induce MT delayed release. In conclusion, the PEHFL may be a promising delivery system for vaginal delivery of medication.

Microstructural analysis of foam by use of NMR R 2 dispersion

The spin–spin relaxation rate R 2 (=1/T 2) in hydrogel foams measured by use of a multiple spin echo sequence is found to be dependent on the echo time spacing. This property, referred to as R 2-dispersion, originates to a large extent from molecular self-diffusion of water within internal field gradients that result from magnetic susceptibility differences between the gel and air phase. Another contribution to the R 2 relaxation rate is surface relaxation. Numerical simulations are performed to investigate the relation between the foam microstructure (the mean air bubble radius and standard deviation of the air bubble radius) and foam composition properties (such as magnetic susceptibilities, diffusion coefficient and surface relaxivity) at one hand and the R 2-dispersion at the other hand. The simulated R 2-dispersions of gel foam are in agreement with the measured R 2-dispersions. By correlating the R 2-dispersion parameters and simulated microstructure properties a semi-empirical relationship is obtained that enables the mean air bubble size to be derived from measured R 2-dispersion curves. The R 2-derived mean air bubble size of a hydrogel foam is in agreement with the bubble size measured with X-ray micro-CT. This illustrates the feasibility of using 1H R 2-dispersion measurements to determine the size of air bubbles in hydrogel foams and of alveoli in lung tissue.

Comparative Efficacy of Topical Versus Systemic Teicoplanin in Experimental Model of Wound Infections

Surgical site infections are the second most common cause of nosocomial infections and, typically, gram-positive pathogens are involved. A mouse model was used to investigate the efficacy of different methods for the treatment of wound infections. A full thickness wound was established on the back subcutaneous tissue of adult male BALB/c mice. A small gauze was placed over each wound and then inoculated with 5 x 10(7) colony-forming units of Staphylococcus aureus. The study included a control group that did not receive any treatment and four contaminated groups treated, respectively, with: (1) drug-free Allevyn (Smith and Nephew Healthcare, Yorkshire, United Kingdom), (2) teicoplanin-soaked Allevyn, (3) drug-free Allevyn and daily intraperitoneal teicoplanin (7 mg/kg) and, finally, (4) teicoplanin-soaked Allevyn and daily intraperitoneal teicoplanin (7 mg/kg). Main outcome measures were quantitative bacterial culture, assessment of vascular endothelial growth factor (VEGF) plasma levels, histological examination with assessment of microvessel density, and of VEGF expression in tissue sections. Data analysis showed that strong inhibition of bacterial growth was achieved in any group treated with intraperitoneal teicoplanin. However, the highest inhibition of bacterial growth was obtained in the group that received teicoplanin-soaked Allevyn and intraperitoneal teicoplanin. Histological examination showed that each treatment modality was able to reduce the delay in wound repair. The most effective treatment appeared to be the local application of teicoplanin-soaked hydro gel foam. The tissue effects were associated with an increase in neovascularization and VEGF expression by endothelial cells and fibroblasts in the granulation tissue. Bacterial colonies also were reduced, especially when teicoplanin was given parenterally. Soaking a hydro cellular foam with an antistaphylococcal agents, such as teicoplanin, may be useful for the management of infected wounds.

Three dimensional radiation dosimetry in lung‐equivalent regions by use of a radiation sensitive gel foam: Proof of principle

A polymer hydrogel foam is proposed as a potential three dimensional experimental dosimeter for radiation treatment verification in low-density tissue such as the lung. A gel foam is created by beating a radiation sensitive polymer gel mixture in an anoxic atmosphere. The mass density of the gel foam is in the order of 0.25-0.35 kg/dm3. Both nuclear magnetic resonance (NMR) spin-spin relaxation rate (R2) and magnetization transfer ratio (MTR) have been used to map the dose distribution from the gel dosimeter. It is found that MTR has significant advantages compared to R2 for mapping the dose distribution in the polymer gel foam dosimeters. The magnetization transfer ratio is found to be less dependent on the density and microstructure of the gel foam dosimeter while spin-spin relaxation dispersion has been observed making the spin-spin relaxation rate dependent on the interecho time interval. Optical microscopy reveals a microstructure that shows great similarity with human lung tissue. It is also shown how NMR hydrogen proton density measurements can be used to map the density distributions in gel dosimeters.

Partition and diffusion of sodium and chloride ions in soft charged foam: the effect of external salt concentration and mechanical deformation.

The partition and diffusion characteristics of an acrylic acid/acrylamide hydrogel, copolymerized in the pores of a polyurethane foam with sodium and chloride ions, were studied by radiochemical methodologies. The hydrogel foam swells by 51%, 80%% and 260% relative to its raw state under bath salt concentrations of 2.0, 1.0, and 0.15 M, respectively. The corresponding partition coefficients are 1.13, 1.29, and 1.99 for sodium (Na+) and 0.89, 0. 85, and 0.65 for chloride (Cl-). The diffusion coefficients are independent of bath concentration and increase linearly with hydration towards their values in water. Deformation affects partition and diffusion solely by dilatation, which determines the swelling and hydration. Comparison of the hydrogel foam with cartilage and intervertebral disc shows considerable similarities and suggests that the same mechanisms control their function.