Biomedical subjects

P K Campbell

Publications and source records attributed to P K Campbell.

6 recordsLinked to original sources

PubMed2001

Evaluation of the SprayGel adhesion barrier in the rat cecum abrasion and rabbit uterine horn adhesion models.

OBJECTIVE: To evaluate the efficacy of a new adhesion barrier in the prevention of postoperative adhesion formation. DESIGN: A double-blind controlled study of the efficacy of SprayGel in reducing postoperative adhesion formation in two animal models. SETTING: Animal care facility of a contract testing laboratory. ANIMAL(S): Sixteen Sprague-Dawley male rats were randomly allocated into two groups in the cecum abrasion model. Twenty New Zealand white female rabbits were randomly allocated into two groups in the uterine horn abrasion model. INTERVENTION(S): In the rat model, the cecum was abraded with gauze and the abdominal wall was abraded with a scalpel. Treated animals received SprayGel coating on injured surfaces; control animals received no treatment. In the rabbit model, uterine horns were abraded with a scalpel. Treated animals received SprayGel coating on injured surfaces; control animals received no treatment. MAIN OUTCOME MEASURE(S): Postoperative adhesion formation. RESULT(S): In the rat model, SprayGel was found to significantly reduce the incidence of adhesions, which formed in 7 of 8 control rats compared with 1 of 8 treated rats. In the rabbit model, SprayGel was found to significantly reduce both the extent and severity of adhesions. CONCLUSION(S): Application of SprayGel in two animal models reduced formation of postoperative adhesions. Further investigation in large animal and clinical settings is warranted.

Abdominal Muscles↗

PubMed2001

Evaluation of a sprayable polyethylene glycol adhesion barrier in a porcine efficacy model.

BACKGROUND: The formation of adhesions following pelvic surgery remains one of the leading causes of infertility, small bowel obstruction and re-operation for pelvic pain. A novel hydrophilic polyethylene glycol based adhesion barrier (SprayGel) is formed by simultaneously spraying two liquid precursors onto surgical sites. The liquids polymerize to form a gel that effectively coats and adheres to tissue. After about 5 days, the hydrogel layer is absorbed and subsequently undergoes renal clearance. It is believed that the presence of such a barrier would inhibit the formation of adhesions following surgical insult. METHODS: A porcine adhesion model was developed wherein bilateral uterine horn transection and re-anastomosis, along with peritoneal side wall excision was performed via laparotomy. In each animal (n = 10, including the pilot study) one pelvic side wall was treated with adhesion barrier, while the contralateral side remained untreated. RESULTS: At second look laparoscopy, 90% of the untreated sites had adhesions, compared with 30% of the treated sites (P = 0.006). Also observed were statistically significant reductions in the adhesion extent (P = 0.029) and adhesion severity scores (P = 0.023) at the treated sites. However, if the pilot study was excluded (n = 8) the differences obtained were no longer significant. CONCLUSIONS: Polyethylene glycol (SprayGel) merits further investigation as an effective barrier to the formation of post-operative adhesions in this porcine model.

Aerosols↗

PubMed1992

A glass/silicon composite intracortical electrode array.

A new manufacturing technique has been developed for creating silicon-based, penetrating electrode arrays intended for implantation into cerebral cortex. The arrays consist of a 4.2 mm x 4.2 mm glass/silicon composite base, from which project 100 silicon needle-type electrodes in a 10 x 10 array. Each needle is approximately 1,500 microns long, 80 microns in diameter at the base, and tapers to a sharp point at the metalized tip. The technique used to manufacture these arrays differs from our previous method in that a glass dielectric, rather than a p-n-p junction, provides electrical isolation between the individual electrodes in the array. The new electrode arrays exhibit superior electrical properties to those described previously. We have measured interelectrode impedances of at least 10(13) omega, and interelectrode capacitances of approximately 50 fF for the new arrays. In this paper, we describe the manufacturing techniques used to create the arrays, focusing on the dielectric isolation technique, and discuss the electrical and mechanical characteristics of these arrays.

Electric Conductivity↗

PubMed1991

A silicon-based, three-dimensional neural interface: manufacturing processes for an intracortical electrode array.

A method has been developed for the manufacture of a "three-dimensional" electrode array geometry for chronic intracortical stimulation. This silicon based array consists of a 4.2 x 4.2 x 0.12 mm thick monocrystalline substrate, from which project 100 conductive, silicon needles sharpened to facilitate cortical penetration. Each needle is electrically isolated from the other needles, and is about 0.09 mm thick at its base and 1.5 mm long. The sharpened end of each needle is coated with platinum to facilitate charge transfer into neural tissue. The following manufacturing processes were used to create this array. 1) Thermomigration of 100 aluminum pads through an n-type silicon block. This creates trails of highly conductive p+ silicon isolated from each other by opposing pn junctions. 2) A combination of mechanical and chemical micromachining which creates individual penetrating needles of the p+ silicon trails. 3) Metal deposition to create active electrode areas and electrical contact pads. 4) Array encapsulation with polyimide. The geometrical, mechanical, and electrical properties of these arrays should make them well suited as interfaces to cortical tissue.

Animals↗

PubMed1990

A 100 electrode intracortical array: structural variability.

A technique has been developed for fabricating three dimensional "hair brush" electrode arrays from monocrystalline silicon blocks. Arrays consist of a square pattern of 100 penetrating electrodes, with 400 microns interelectrode spacing. Each electrode is 1.5mm in length and tapers from about 100 microns at its base to a sharp point at the tip. The tips of each electrode are coated with platinum and the entire structure, with the exception of the tips, is insulated with polyimide. Electrical connection to selected electrodes is made by wire bonding polyimide insulated 25 microns diameter gold lead wires to bonding pads on the rear surface of the array. As the geometrical characteristics of the electrodes in such an aray will influence their electrical properties (such as impedance, capacitance, spreading resistance in an electrolyte, etc.) it is desirable that such an array have minimal variability in geometry from electrode to electrode. A study was performed to determine the geometrical variability resulting from our micromachining techniques. Measurements of the diameter of each of the 100 electrodes were made at various planes above the silicon substrate of the array. For the array that was measured, the standard deviation of the diameters was approximately 9% of the mean diameter near the tip, 8% near the middle, and 6% near the base. We describe fabrication techniques which should further reduce these variabilities.

Animals↗

PubMed1989

A chronic intracortical electrode array: preliminary results.

Two sets of electrode arrays made of either 25- or 50-microns-diameter Teflon-insulated platinum-iridium wire and Teflon have been developed for chronic intracortical electrical stimulation. Cortical histological studies were performed following acute and chronic implantation in cats. While some neural damage resulted from the implantations of either array configuration, a unique set of problems was associated with each diameter wire. Arrays with 50-microns electrodes and lead wires tended to maintain interelectrode spacing upon implantation, but the percutaneous leads retained residual stress which made array implantation difficult. Arrays with 25-microns electrodes and lead wires suffered from changes in interelectrode spacing upon implantation, but were much easier to manipulate during surgery. Both array configurations demonstrated some movement after implantation. It is concluded that a chronic intracortical stimulating electrode array of this geometry should have the following properties: 1) the penetrating electrodes and supporting substrate must be stiff (to maintain interelectrode spacings upon implantation), and 2) the percutaneous leads must be extremely flexible (to avoid array movement after implantation).

Animals↗