Profile of rhBMP-2 release from collagen minipellet and induction of ectopic bone formation.

For a cylindrical controlled-release formulation using collagen as a carrier, called the minipellet (MP), which contains rhBMP-2, the relationship between the diameter of MPs and rhBMP-2 release profiles was investigated, and its effect in inducing bone formation was evaluated. Samples with three different diameters were tested for each of the following formulations: MP without additives, MP with 10% (w/w) glutamic acid (Glu) and 20% (w/w) alanine (Ala), and MP with 20% (w/w) Glu and 20% (w/w) Ala. The results of the in vitro release test and the amount of rhBMP-2 remaining in the MPs after subcutaneous implantation into mice were compared among different samples.

Controlled release of rhBMP-2 from collagen minipellet and the relationship between release profile and ectopic bone formation.

The purpose of this study was to examine the effects of various additives on the profiles of rhBMP-2 release from minipellet, which is a sustained release formulation for protein drugs using collagen as a carrier, and to examine the influence of varying release profiles on ectopic bone formation. When the amount of rhBMP-2 remaining in the preparation after subcutaneous implantation to mice was examined, it was found that the addition of sucrose, glucose, PEG4000, alanine (Ala) or acacia in a concentration of 20% (w/w) to the minipellet with 5% (w/w) of rhBMP-2 did not accelerate the drug release in a noticeable manner, while the addition of sodium chondroitin sulfate, glutamic acid (Glu) or citric acid accelerated the release of rhBMP-2 markedly. When two types of minipellets (a fast release type added with 20% Glu and 20% Ala and a slow release type without additives) containing varying amounts of rhBMP-2 were implanted subcutaneously to mice, the soft X-ray observation, histological examination and measurement of calcium formation 3 weeks after implantation revealed extensive ectopic bone formation in mice implanted with the fast release type preparation.

Atelocollagen for protein and gene delivery.

Recent progress in recombinant gene technology and cell culture technology has made it possible to use protein and polynucleotides as effective drugs. However, because of their short half-lives in the body and the necessity of delivering to target site, those substances do not always exhibit good potency as expected. Therefore, delivery systems of such drugs are important research subjects in the field of pharmacology, and to prolong the effect of these drugs, many studies are being conducted to control the release of proteins and polynucleotides from various carrier materials.

Design of long-acting formulation of protein drugs with a double-layer structure and its application to rhG-CSF.

In order to design a sustained-release formulation of protein drugs characterized by excellent long-acting properties without an initial burst, a new double-layer minipellet (DL-MP) in which the lateral side of a matrix-type sustained-release formulation 'minipellet' using collagen as a carrier was coated with collagen was designed, and its performance was evaluated. In a DL-MP using bovine serum albumin (BSA) as a model drug, the initial burst observed with a single-layer minipellet (SL-MP) was effectively inhibited in an in vitro release test, and the addition of additives such as chondroitin sulfate (CS) permitted control of release rate. This formulation of recombinant human granulocyte colony-stimulating factor (rhG-CSF) was then prepared, and its characteristics were determined in normal rats.

Novel drug delivery device using silicone: controlled release of insoluble drugs or two kinds of water-soluble drugs.

Drug release mechanism from silicone carrier differs depending on physicochemical properties of the drug. So far, there have been few reports on controlled release of insoluble drug and on simultaneous release of two kinds of water-soluble drugs. The purposes of this study are to establish methods for (1).

Novel method to control release of lipophilic drugs with high potency from silicone.

Silicone has been utilized as a carrier material for sustained release system of lipophilic drugs. Extensive studies revealed that drug release rate is influenced by factors such as physicochemical properties of the drug and additives.(1-5)) When a lipophilic drug is highly potent at low concentrations, the drug release rate should be strictly controlled so as to avoid side effects.