PubMed · 1808246
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M Suzuki, N Endoh, I Nakagawa, F Nakamura. 1991. [High-performance membranes].. https://pubmed.ncbi.nlm.nih.gov/1808246/
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Investigators that require the chronic implantation of hardware on the non-human primate skull are often challenged with the possible failure of head implants. To improve the success rate of our head implants, titanium anchor screws, referred to as titanium endosseous implants, were implanted in the skulls of six macaques. Techniques adapted from the processing of dentures were utilized to pre-fabricate an acrylic "skull cap", which provided the mechanical support structure for our study-specific hardware. A two-stage procedure adapted from dentistry (Brånemark et al., 1977) was employed for the placement of titanium endosseous implants in the skull. This two-stage technique incorporates the principles of osseointegration and a healing period. Of the six skull-anchored implants prepared implementing the methods described in this paper, we have not experienced any failures. Additionally, all of the titanium endosseous implants examined post mortem were functionally successful (n=30). Histology results confirmed that there was healthy bone in direct contact with the titanium endosseous implants. The dense cortical bone of the macaque skull is ideal for the implantation of titanium endosseous implants. Titanium endosseous implants have provided secure, functional anchor points for the attachment of hardware to the macaque skull and have resulted in healthy, stable head implants that can remain on the skull for extended periods of time.
The enhancing effect of several terpenes (thymol, menthone and 1,8-cineole) in the percutaneous permeation of piroxicam (Px), either passive or iontophoretically, was investigated. These terpenes were applied, on the skin membrane, as a passive and iontophoretic skin pretreatment. Px was delivered from carbopol gels containing hydroxypropyl-beta-cyclodextrin (2% w/w Px). An increase in Px flux values, both passive and iontophoretic after skin pretreatment with 5% terpenes/50% EtOH, was found to be in the following order: thymol>menthone>1,8-cineole. Iontophoretic skin pretreatment with terpenes produced a slight increase in the passive flux of Px, in comparison with the passive skin pretreatment. This result indicated that iontophoresis could modify the skin morphology and consequently, increase the passive transport of Px. However, when Px was transported iontophoretically, passive skin pretreatment with terpenes, produced higher flux values than iontophoretic skin pretreatment. These results could be explained by the fact that with the iontophoretic pretreatment, terpenes could penetrate into the skin and limitate the movement of the ionized species, across the skin, during the iontophoretic experiments. The amount of Px retained in the skin after all experiments was related to flux values across skin.
A new chemical cross-linking scheme was utilized for the formation of degradable poly(ethylene glycol) hydrogels suitable for the delivery of protein drugs. An aqueous solution containing a PEG-multiacrylate and solid particles of albumin was mixed with an aqueous solution containing a PEG-dithiol, rapidly producing a cross-linked hydrogel through a Michael-type addition reaction. For some formulations, it was observed that about 65% of the incorporated protein was released with zero-order kinetics over a period of about 4 days. By changing the functionality of the cross-linker, the release of protein could even be delayed for about 4 days, followed by zero-order release. The mechanism for release appeared to be a combination of slow dissolution of protein in the presence of PEG and hindered diffusion of protein through the gel. The cross-linking of the gels was studied rheometrically, and the hydrolytic degradation of the gels was characterized by measuring the swelling of the gels. Biochemical analysis of the released proteins demonstrated that the polymers reacted with each other, but not with proteins. Utilizing the Flory-Rehner and Peppas-Merrill equations, a framework for modeling the protein release from the gels is described.