Magnetic nanoparticles as gene delivery agents: enhanced transfection in the presence of oscillating magnet arrays.

Magnetic nanoparticle-based gene transfection has been shown to be effective in combination with both viral vectors and with non-viral agents. In these systems, therapeutic or reporter genes are attached to magnetic nanoparticles which are then focused to the target site/cells via high-field/high-gradient magnets. The technique has been shown to be efficient and rapid for in vitro transfection and compares well with cationic lipid-based reagents, producing good overall transfection levels with lower doses and shorter transfection times. In spite of its potential advantages (particularly for in vivo targeting), the overall transfection levels do not generally exceed those of other non-viral agents. In order to improve the overall transfection levels while maintaining the advantages inherent in this technique, we have developed a novel, oscillating magnet array system which adds lateral motion to the particle/gene complex in order to promote transfection. Experimental results indicate that the system significantly enhances overall in vitro transfection levels in human airway epithelial cells compared to both static field techniques (p<0.005) and the cationic lipids (p<0.001) tested. In addition, it has the previously demonstrated advantages of magnetofection-rapid transfection times and requiring lower levels of DNA than cationic lipid-based transfection agents. This method shows potential for non-viral gene delivery both in vitro and in vivo.

System for the pH-dependent release of a dye in model dental restorations.

We are developing a system for detecting recurrent caries under dental restorations. The controlled release of dyes under conditions of likely demineralization will alert the dentist to potential secondary caries. Production of acidic species is a characteristic of caries activity; hence, the system uses pH-sensitive polymers to release markers when the pH at the cavity wall of the restored tooth is below 6.5. The objectives of this investigation were to test the hypotheses that (1) the proposed system can be designed to release detectable marker continuously for at least six months in a simulated carious environment, and (2) the transient pH changes in the oral cavity caused by simulated dietary intake will not induce premature marker release from the pH-sensitive polymer placed beneath restorations. Two types of dye-loaded microspheres based on styrene, vinylpyridine, and divinylbenzene were prepared and placed on the floor of model cavity preparations made from an acrylic rod. Each model cavity was restored with a hybrid dental composite, placed in a vial with 5 mL of sodium-lactate/lactic-acid base buffer solution, and stored at 37 degrees C. Solutions of three different pH values were used: 2.86, 4.73, and 6.39. The dye release into storage media was monitored periodically with a UV/VIS spectrophotometer. Results showed that the duration could extend beyond six months for pH > 4.73, and that transient oral pH changes are not likely to result in premature dye release. The data indicate that it would take approximately 21 days for the acidic agent external to the restoration to initiate dye release from restored sites.

Water and abrasive effects on three-body wear of composites.

The degrees of in vitro three-body wear resistance of a hybrid, a small-particle, and a microfilled composite were determined after water storage for up to 24 months. The hybrid composite was the most wear-resistant, while the microfilled composite showed the most wear. The hybrid composite showed no loss of wear resistance as a result of water storage. The small-particle composite showed a decrease in wear resistance after water storage only when tested with silicon carbide abrasive. The wear resistance of the microfilled composite decreased following water storage when tested with either a soft (CaCO3) or a hard (SiC) abrasive. For all composites, the soft abrasive was not capable of causing preferential wear of the polymer matrix, as observed on in vivo specimens. Instead, the filler particles became flattened, with minimal loss of interparticle substance. The hard abrasive did cause preferential wear of the matrix. All composites absorbed water and leached silicon during water storage, indicating that the filler-polymer bond was attacked by hydrolytic degradation. Scanning electron microscopic evaluation of the three-body wear specimens indicated that the in vitro wear method did not duplicate in vivo wear conditions (e.g., the hard abrasive caused excessive wear and chipping of the filler particles in vitro, a pattern that was not usually observed in vivo). Filler-polymer de-bonding was observed on in vivo specimens of all the composites, while it was found only on the in vitro microfilled composite specimens. These findings suggest that filler dislodging is a complex process that cannot be simulated with the in vitro wear method used in this study, not even after prolonged water storage.

The effect of exercise on the circumvaginal muscles in postpartum women.

The effect of exercise on pressure developed by the circumvaginal muscles (CVM) in postpartum women was studied. The CVM assessment system described earlier by Dougherty, Abrams, and McKey used an intravaginal balloon device (IVBD) developed from an impression and model of the vagina. The system (IVBD, pressure transducer and strip chart recorder) provided permanent CVM pressure tracings with high test-re-test reliability (n = 16; r = .85) for maximum pressure (MP). The hypothesis in the research reported here was that exercise with and without an IVBD, when compared to no exercise, would result in significantly higher MP and pressure over time (POT). Forty-five healthy PP volunteers were randomly assigned to a 10-minute per day home training program, for six weeks. The baseline and six-week assessments consisted of CVM pressure tracings during contraction. Dependent variables were MP (highest pressure attained) and POT (area under the pressure curve). Although no significant differences were found between the home training groups, greater improvement was found in the exercise groups. Variability within subjects partly accounts for the results. Pressure changes before and after pregnancy and before and after CVM exercise are demonstrated in a case study. The findings support the use of CVM exercise in the postpartum.

The dynamic characteristics of the circumvaginal muscles.

Circumvaginal muscle (CVM) maximum pressure was studied as related to the postpartal period, parity, type of birth, episiotomy, age, breastfeeding, physical activity, body mass, stress urinary incontinence, and orgasm in a sample of 98 healthy postpartal and nonpostpartal women. Circumvaginal muscle pressure tracings were obtained from these women using a pressure-sensitive, intravaginal balloon device. Correlations between circumvaginal muscle maximum pressures and episiotomy, age, breastfeeding, physical activity, body mass, stress urinary incontinence, and orgasm were either not significant or only weakly significant. However, Duncan's multiple range test showed differences in the maximum pressures between groups (nulliparous, parity greater than 0, cesarean delivery, and vaginal delivery) and indicated that vaginal birth has a marked weakening effect on the circumvaginal muscles.

Ultrastructure of whewellite kidney stones: electron-analytical investigation.

The investigation of the degree of interpenetration between the two component phases of whewellite kidney stones, the protein matrix and calcium oxalate monohydrate crystallites, is extended by a technique of microchemical analysis, employing X-ray photoelectron spectroscopy (XPS). The technique involves determining the surface elemental (hence chemical) composition of fractured whewellite stones. Comparison with the bulk composition of about 95% COM and 5% matrix yielded information on the fracture path, hence on the spatial distribution of the two phases. The results showed large increases in matrix signal upon fracture, confirming that the minor phase, matrix, which is expected to provide an easy path for fracture, pervades the structure down to the level of individual crystallites.