Self-Expandable Electrode Based on Chemically Polished Nickel–Titanium Alloy Wire for Treating Endoluminal Tumors Using Bipolar Irreversible Electroporation

The application of irreversible electroporation (IRE) to endoluminal organs is being investigated; however, the current preclinical evidence and optimized electrodes are insufficient for clinical translation. Here, a novel self-expandable electrode (SE) made of chemically polished nickel–titanium (Ni–Ti) alloy wire for endoluminal IRE is developed in this study. Chemically polished heat-treated Ni–Ti alloy wires demonstrate increased electrical conductivity, reduced carbon and oxygen levels, and good mechanical and self-expanding properties. Bipolar IRE using chemically polished Ni–Ti wires successfully induces cancer cell death. IRE-treated potato tissue shows irreversibly and reversibly electroporated areas containing dead cells in an electrical strength-dependent manner. In vivo study using an optimized electric field strength demonstrates that endobiliary IRE using the SE evenly induces well-distributed mucosal injuries in the common bile duct (CBD) with the overexpression of the TUNEL, HSP70, and inflammatory cells without ductal perforation or stricture formation. This study demonstrates the basic concept of the endobiliary IRE procedure, which is technically feasible and safe in a porcine CBD as a novel therapeutic strategy for malignant biliary obstruction. The SE is a promising electrical energy delivery platform for effectively treating endoluminal organs

Schematic image of an absorbable magnesium stent to manage ETD showing prevention of stent-induced tissue hyperplasia and maintaining the ET patency.

Schematic image of an absorbable magnesium stent to manage ETD showing prevention of stent-induced tissue hyperplasia and maintaining the ET patency.</p

The Mg stent and the technical steps of ET stent placement under endoscopic guidance.

Photographs showing (A) the Mg stent loaded onto a balloon catheter and (B) when fully expanded. (C) Endoscopic image showing the nasopharyngeal ostium (arrowheads). (D) The steerable guiding sheath (arrows) was inserted into the nasopharyngeal ostium. (E) The balloon catheter crimped with the Mg stent (arrowheads) is advanced into the ET. (F) The balloon catheter was fully inflated with saline. (G) After verifying the fully expanded stent (arrows), the sheath with the balloon catheter was removed. (H) An endoscopic image of the Mg stent (arrowheads) in the porcine ET. Note. Mg, magnesium; ET, Eustachian tube.</p

Representative endoscopic and CT images of the stented ET over time.

(A) Endoscopic images taken immediately after stent placement, showing the proximal end of the Mg stent (arrows) in the porcine ET. The proximal end of the stent with mild secretion (arrows) is observed around the Mg stent at two weeks, while the Mg stent is not observed at four weeks (arrowheads). (B) 3D-reconstructed CT images of the degraded Mg stent showing a residual Mg stent with a collapsed distal end at two weeks and only a small piece of the Mg stent at four weeks. Note. CT, computed tomography; Mg, magnesium; ET, Eustachian tube.</p

Representative histological images of the porcine ET and histological findings.

(A) Histological images showing the submucosal tissue hyperplasia increased at two weeks and then significantly decreased at four weeks. (B) Histological results of the thickness of submucosal tissue hyperplasia and the degree of inflammatory cell infiltration in the proximal and distal portions of the stented ET over time after the Mg stent placement. Note. Mg, magnesium; ET, Eustachian tube.</p

Surface morphologies of the Mg stent and mass loss rates.

(A) SEM images showing the size and number of the cracks increasing over time (arrows) on the surface of Mg stent samples obtained at one, two, and four weeks, respectively. (B) The bridges (arrows) between the struts are disconnected, and the strut was sequentially separated. (C) A graph depicting the mass loss rates of the Mg stent over a four-week period. Note. Mg, magnesium; SEM, scanning electron microscopy.</p

Growth and yield of a tropical rainforest in the Brazilian Amazon 13 years after logging

Successive inventories of a silvicultural experiment in terra firme rain forest within the Tapajós National Forest in the Brazilian Amazon are examined to provide guidelines for operational forest management on a sustainable basis. The experiment was logged in 1979 without additional silvicultural treatment, but included protection from further logging and encroachment (`log and leave'). Thirty six permanent plots established in 1981 were remeasured in 1987 and 1992. Logging changed the canopy structure and altered the composition of the stand, reducing the number of shade tolerant species and stimulating light demanding species. There was a net increase in stem number and stand basal area during the 11 year observation period, and this trend also holds for most of the individual species. The stand basal area 13 years after logging was about 75% of that in a comparable unlogged forest. Logging stimulated growth, but this effect was short lived, lasting only about 3 years, and current growth rates are similar to those in the unlogged forest. Between the first and second remeasures, average diameter increment decreased from 0.4 to 0.2 cm year-1, mortality remained relatively constant at 2.5% year-1, while recruitment (at 5 cm diameter at breast height) decreased from 5 to 2%. Total volume production declined from approximately 6 to 4 m3 ha-1 year-1, while commercial production remained about 0.8 m3 ha-1 year-1. New commercial species increased the commercial volume in 1992 from 18 to 54 m3 ha-1, and the increment to 1.8 m3 ha-1 year-1. Results from this experiment provide the first quantitative information for management planning in the Tapajós Forest, and may guide the choice of cutting cycle and annual allowable cut. Silvicultural treatment to stimulate growth rates in forest areas zoned for timber production should be considered as a viable management option. Extrapolations of these results to an anticipated 30-35 year cutting cycle must be interpreted with caution. Ongoing remeasurement and analysis of these and other plots over the next 30 years or more are necessary to provide a stronger basis for management inferences

EW-7197 eluting nano-fiber covered self-expandable metallic stent to prevent granulation tissue formation in a canine urethral model - Fig 1

<p>Representative optical images of (A) Nanofiber-covered, self-expandable metallic stent and (B) scanning electron micrographs of EW-7197 loaded nanofibers. The scale bars are 30 μm and 10 μm.</p

EW-7197 eluting nano-fiber covered self-expandable metallic stent to prevent granulation tissue formation in a canine urethral model - Fig 5

<p>Representative microscopic images (hematoxylin and eosin staining magnification × 2 [A,B] and Masson’s trichrome staining magnification × 5 [C,D]) of histological sections at 8 weeks after stent placement. The thickness of papillary projection (arrows) was significantly increased in the CS group (A) compared to the DS group (B). Arrowhead = stent struts (A,B). The degree of collagen deposition (arrowheads) was significantly greater in the CS group (C) than the DS group (D). The number of epithelial layers (arrows) in the CS group (C) was significantly higher than the DS group (D). CS: control stent, DS: drug stent.</p

Retrograde urethrographic findings after stent placement in canine urethra.

<p>Retrograde urethrographic findings after stent placement in canine urethra.</p