Physiological and functional responses of water-cooled versus traditional radiofrequency ablation of peripheral nerves in rats

BACKGROUND AND OBJECTIVES

Several clinical studies have focused on assessing the effectiveness of different radiofrequency ablation (RFA) modalities in pain management. While a direct head-to-head clinical study is needed, results from independent studies suggest that water-cooled RFA (CRFA) may result in longer lasting pain relief than traditional RFA (TRFA). The primary purpose of this study was, therefore, to investigate in a preclinical model, head-to-head differences between the two RFA technologies.

METHODS

RFA was performed in a rat sciatic nerve model (n=66) in two groups: (1) TRFA or (2) CRFA. The surgeon was not blinded to the treatment; however, all the physiological endpoints were assessed in a blinded fashion which include histological, MRI, and nerve function assessment via electromyography.

RESULTS

The energy delivered by the generator for CRFA was significantly higher compared with TRFA. Histological staining of nerves harvested immediately following CRFA exhibited extended length and multiple zones of thermal damage compared with TRFA-treated nerves. MRI scans across 4 weeks following treatment showed edematous/inflammatory zones present for longer times following CRFA. Finally, there was greater attenuation and prolonged loss of nerve function measured via electromyography in the CRFA group.

CONCLUSIONS

This study shows that CRFA has greater energy output, as well as more pronounced structural and functional changes elicited on the peripheral nerves compared with TRFA. While these preclinical data will need to be confirmed with a large clinical randomized controlled trial, we are encouraged by the direction that they may have set for those trials.

D-Optimal mixture experimental design for stealth biodegradable crosslinked docetaxel-loaded poly-ε-caprolactone nanoparticles manufactured by dispersion polymerization

We report here our efforts on the development of stealth biodegradable crosslinked poly-ε-caprolactone nanoparticles by free radical dispersion polymerization suitable for the delivery of bioactive agents. The uniqueness of the dispersion polymerization technique is that it is surfactant free, thereby obviating the problems known to be associated with the use of surfactants in the fabrication of nanoparticles for biomedical applications. Aided by a statistical software for experimental design and analysis, we used D-optimal mixture statistical experimental design to generate thirty batches of nanoparticles prepared by varying the proportion of the components (poly-ε-caprolactone macromonomer, crosslinker, initiators and stabilizer) in acetone/water system. Morphology of the nanoparticles was examined using scanning electron microscopy (SEM). Particle size and zeta potential were measured by dynamic light scattering (DLS). Scheffe polynomial models were generated to predict particle size (nm) and particle surface zeta potential (mV) as functions of the proportion of the components. Solutions were returned from simultaneous optimization of the response variables for component combinations to (a) minimize nanoparticle size (small nanoparticles are internalized into disease organs easily, avoid reticuloendothelial clearance and lung filtration) and (b) maximization of the negative zeta potential values, as it is known that, following injection into the blood stream, nanoparticles with a positive zeta potential pose a threat of causing transient embolism and rapid clearance compared to negatively charged particles. In vitro availability isotherms show that the nanoparticles sustained the release of docetaxel for 72 to 120 hours depending on the formulation. The data show that nanotechnology platforms for controlled delivery of bioactive agents can be developed based on the nanoparticles.

Formation of particles in aqueous infusions of the medical plant Harungana madagascariensis

In some aqueous plant extracts the formation of nanoparticles, microparticles and macroparticles has been observed. In the present investigation the particle formation in aqueous infusions of Harungana madagascariensis LAM. EX. POIR., a medicinal plant, was investigated using photon correlation spectroscopy (PCS) and scanning electron microscopy (SEM). The results show that nanoparticles with mean diameters of 220 nm are formed in aqueous infusions of the dried leaves of Harungana. The particles have an almost spherical shape. In aqueous infusions of the dried stem bark nanoparticles with a mean diameter of 242 nm (PCS) are observed at 25 degrees C. The particle size distribution has a maximum in the range of 200 nm to 300 nm. Nanoparticles can be detected in infusions of the leaves and the bark in the range of 25 degrees C to 55 C. The mean diameter of the nanoparticles in preparations of the bark is temperature dependent: At 55 degrees C the mean diameter is 144 nm, at 30 degrees C 197 nm and at 25 degrees C 242 nm. Lower temperatures result in higher count rates. In infusions of the leaves the mean diameters vary between 220 (25 degrees C) and 139 nm (55 degrees C). The particle formation was investigated at pH 2.2, 4.0 and 7.4 at 37 degrees C. Nanoparticles are detected in infusions of the leaves and the stem bark at each pH. The pH value has an influence on the mean diameter and the count rate.