Recent developments in the synthesis and utilization of poly (ortho esters)

Heller, Jorge; Maa, Y. F.; Wüthrich, Patrick; Ng, Shu Hang; Duncan, Ruth

doi:10.1016/0168-3659(91)90026-a

Cited by 20 publications

(5 citation statements)

References 12 publications

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“…In addition, the degradation of POEs is generally confined to the surface layer, essentially resulting in an erosion‐controlled release of encapsulated compounds. In accordance, long‐term zero‐order release has been shown in several studies on low molecular weight drugs encapsulated in (semisolid) POE 2–7. The biocompatibility of these POEs is good, and the degradation products consist of relatively harmless compounds like pentaerythritol and propionic acid 8.…”

Section: Introductionmentioning

confidence: 66%

“…The biocompatibility of these POEs is good, and the degradation products consist of relatively harmless compounds like pentaerythritol and propionic acid 8. Whereas earlier types of POE required the admixing of an acidic compound to result in POE degradation,2,4,9 the newer types contain a latent acid in the backbone 6. Indiffusion of water and subsequent ester degradation result in a local drop of pH, which in turn catalyzes the ortho ester degradation.…”

Section: Introductionmentioning

confidence: 99%

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Semisolid, Self-Catalyzed Poly(Ortho Ester)s As Controlled-Release Systems: Protein Release and Protein Stability Issues

Weert

Steenbergen

Cleland³

et al. 2002

Journal of Pharmaceutical Sciences

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Section: Introductionmentioning

confidence: 66%

Section: Introductionmentioning

confidence: 99%

Semisolid, Self-Catalyzed Poly(Ortho Ester)s As Controlled-Release Systems: Protein Release and Protein Stability Issues

Weert

Steenbergen

Cleland³

et al. 2002

Journal of Pharmaceutical Sciences

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“…This semi-solid polymer is currently under investigation regarding its biocompatibility (3). Controlled peptide delivery (4,5) and ophthalmic implant injections, releasing the antimetabolite 5-fluorouracil (6), have been reported recently.…”

Section: Introductionmentioning

confidence: 99%

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Merkli

Heller²,

Tabatabay

et al. 1994

Pharmaceutical Research

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Radiation sterilization is becoming increasingly popular for the sterilization of many pharmaceutical products. Although this technique is not limited to the sterilization of polymers, it is probably the most suitable method for such materials. This method however suffers several drawbacks. The sterilization of a product must lead to a safety level of 10(-6), i.e. one chance in a million to find a contaminated sample. In many cases, this assurance of sterility can be achieved by using a uniform treatment dose of 2.5 Mrad, recommended by the pharmacopeia. We investigated the possibility of using doses of radiation inferior to 2.5 Mrad to sterilize a semi-solid poly(ortho ester) (POE) developed for use as carrier in controlled drug delivery. After determination of the initial bioburden, the polymer was intentionally contaminated with the bioindicator Bacillus pumilus E 601. Following exposure to gamma irradiation, the D10 value of the radio resistant bioindicator was determined. Using the initial contamination value, the reduction factor D10 and the safety level, it is possible to calculate an optimal sterilizing dose for POE. All polymers are affected by ionizing radiation and the amount of radiation which produces a significant change in properties may vary from one polymer to the other. A molecular weight and dynamic viscosity decrease resulting from backbone cleavage was observed for this POE at a dose lower than 2.0 Mrad. Evaluation of the structure using 1H-NMR, 13C-NMR and IR analysis shows that for doses higher than 2.0 Mrad, another degredation process takes place.(ABSTRACT TRUNCATED AT 250 WORDS)

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“…[14][15][16][17][18] Since the second hydrolysis is much slower, no autocatalysis is observed (Fig. 2).…”

Section: Poe Degradationmentioning

confidence: 99%

Subconjunctival biocompatibility of a viscous bioerodable poly(ortho ester)

Zignani

Bernatchez

Minh

et al. 1998

J. Biomed. Mater. Res.

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The biocompatibility of a viscous poly(ortho ester) (POE) intended for prolonged intraocular drug delivery was studied. This hydrophobic and bioerodable carrier was subconjunctivally injected in rabbits and evaluated both clinically and histologically. To assess the cause of the triggered transient acute inflammatory reaction, the two monomers, the intermediate and final degradation products, and the local toxicity of different solvents used during the polymer preparation were tested. Since the two initial monomers and the intermediate degradation products induced only moderate inflammation, the main acute inflammatory reaction is attributed to the formation of an acidic by-product which has been monitored in vitro by measuring the progressive decrease of the environmental pH. The influence of the sterilization procedure on tissue biocompatibility was established by comparing two polymers of similar molecular weight: one after gamma-sterilization, and an aseptically synthesized one. The biocompatibility was significantly improved by avoiding irradiation of the polymer.

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Recent developments in the synthesis and utilization of poly (ortho esters)

Cited by 20 publications

References 12 publications

Semisolid, Self-Catalyzed Poly(Ortho Ester)s As Controlled-Release Systems: Protein Release and Protein Stability Issues

Semisolid, Self-Catalyzed Poly(Ortho Ester)s As Controlled-Release Systems: Protein Release and Protein Stability Issues

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Subconjunctival biocompatibility of a viscous bioerodable poly(ortho ester)

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