A dexamethasone-loaded PLGA microspheres/collagen scaffold composite for implantable glucose sensors.

We have developed a new dexamethasone (Dex)-loaded poly(lactic-co-glycolic acid) microspheres/porous collagen scaffold composite for implantable glucose sensors. The scaffolds were fabricated around the sensing element of the sensors and crosslinked using nordihydroguaiaretic acid (NDGA). The microspheres containing Dex were incorporated into the NDGA-crosslinked collagen scaffold by dipping in microsphere suspension in either water or Pluronic.

A novel porous collagen scaffold around an implantable biosensor for improving biocompatibility. II. Long-term in vitro/in vivo sensitivity characteristics of sensors with NDGA- or GA-crosslinked collagen scaffolds.

We have developed a new 3D porous and biostable collagen scaffold for implantable glucose sensors. The scaffolds were fabricated around the sensors and crosslinked using nordihydroguaiaretic acid (NDGA) or glutaraldehyde (GA) to enhance physical and biological stability. The effect of the scaffolds on sensor function and biocompatibility was examined during long-term (>or=28 days) in vitro and in vivo experiments and compared with control bare sensors.

Use of hydrogel coating to improve the performance of implanted glucose sensors.

In order to protect implanted glucose sensors from biofouling, novel hydrogels (146-217% water by mass) were developed based on a copolymer of hydroxyethyl methacrylate (HEMA) and 2,3-dihydroxypropyl methacrylate (DHPMA). The porosity and mechanical properties of the hydrogels were improved using N-vinyl-2-pyrrolidinone (VP) and ethyleneglycol dimethacrylate (EGDMA). The results of SEM and DSC FT-IT analyses showed that the hydrogel (VP30) produced from a monomeric mixture of 34.

Synthesis and performance of novel hydrogels coatings for implantable glucose sensors.

Novel hydrogel polymers were prepared, characterized, coated on implantable glucose sensors, and tested in vitro and in vivo. The effects of 2,3-dihydroxypropyl methacrylate (DHPMA) on the swelling, morphology, glass transition (T(g)), and water structure were studied. The results show that the degree of swelling increases with increasing DHPMA content.

A novel porous collagen scaffold around an implantable biosensor for improving biocompatibility. I. In vitro/in vivo stability of the scaffold and in vitro sensitivity of the glucose sensor with scaffold.

A new 3D porous and biostable collagen scaffold has been developed to improve the biocompatibility of implantable glucose sensors by minimizing tissue reactions while stimulating angiogenesis around the sensors. The novel collagen scaffold was crosslinked using nordihydroguaiaretic acid (NDGA) to enhance biostability. NDGA-treated collagen scaffolds were stable without physical deformation in the subcutaneous tissue of rats for 4 weeks.

Study of the effects of tissue reactions on the function of implanted glucose sensors.

The relationship between tissue reactions to a subcutaneously implanted glucose sensor and the function of the sensor was evaluated over a period of 4-weeks using tubular, porous polyvinyl alcohol (PVA) sponges implanted subcutaneously in rats. The PVA sponges were used as scaffolds in which the foreign body response could develop. Coil-type glucose sensors were then placed in the center of the PVA sponges and tested on day 3, and weekly thereafter.

An investigation of long-term performance of minimally invasive glucose biosensors.

Objective: The long-term performance stability of minimally invasive glucose biosensors was evaluated in vitro and in vivo.

Methods: Coil-type glucose biosensors were constructed using an epoxy-polyurethane membrane. Seven sensors were continuously polarized for 12 weeks in a 5 mM glucose-phosphate-buffered saline (PBS) solution, and the sensor sensitivities were tested weekly.

Strategies for testing long-term transcutaneous amperometric glucose sensors.

Objectives: Transcutaneous and embedded devices were developed for use in characterizing the in vivo performance of subcutaneously implanted glucose sensors. The devices were used as a portal for accessing electrochemical glucose sensors from the exterior. They were designed to prevent the sensors from being pulled out of the animals and the sensor leads from breaking.

A long-term flexible minimally-invasive implantable glucose biosensor based on an epoxy-enhanced polyurethane membrane.

This paper describes the preparation method as well as the in vitro and in vivo evaluation of a novel flexible glucose biosensor designed for long-term subcutaneous implantation. An epoxy-enhanced polyurethane membrane, which includes ca. 30-40% epoxy resin adhesive and 50-70% polyurethane, has been developed and used for the first time as the outer protective membrane of the sensor.

Coil-type implantable glucose biosensor with excess enzyme loading.

As part of our overall long-term objective of designing a glucose sensor for long-term subcutaneous implantation, a coil-type implantable glucose sensor loaded with excess glucose oxidase (GOD) inside the coils of a 0.125mm diameter coiled platinum-iridium wire has been developed. The excess GOD was immobilized in a glutaraldehyde/bovine serum albumin (BSA) gel reinforced with cotton and located inside the coils chamber of the sensor.

Electrochemistry of metal phthalocyanines in organic solvents at variable pressure.

High-pressure electrochemical investigations of representative metallophthalocyanines in solution are reported. The selected systems were ZnPc, CoPc, FePc, and CoTNPc (Pc = phthalocyanine, TNPc = tetraneopentoxyphthalocyanine) in several donor solvents and (for CoTNPc) dichlorobenzene, with [Bu(4)N][ClO(4)] as supporting electrolyte and a conventional Pt electrode referred to Ag(+)(CH(3)CN)/Ag. Electrode reaction volumes deltaV(cell) for CoTNPc and ZnPc show that consecutive ring reductions result in progressive increases in electrostriction of solvent in accordance with Drude-Nernst theory.