RADIO-IODINATION OF NEUROTROPHINS AND THEIR DELIVERY IN-VIVO - ADVANTAGES OF MEMBRANE FILTRATION AND THE USE OF DISPOSABLE SYRINGES

This paper reports two simple improvements for the radio-iodination of neurotrophins and their delivery in vivo. (1) Neurotrophins can be ef fectively separated from free iodide by using membrane filtration devi ces. Seven methods for the separation of free iodide are compared, inc luding dialysis, gel filtration, and membrane filtration. Membrane fil tration of the iodinated protein has several important advantages over dialysis or gel filtration. These include the precise control over th e final concentration; excellent recovery of the neurotrophin; easy an d inexpensive procedure; performance of the entire procedure in a fume hood; and reduced volume of radioactive waste. (2) Disposable, inexpe nsive syringes are suitable for the delivery of small volumes of radio -iodinated or non-radioactive neurotrophins. Plastic disposable insuli n syringes are compared with Hamilton syringes. The ejection volume of the disposable syringes is surprisingly reliable in the dose range 2- 15 mu 1. Their in vivo performance was tested by injections in the eye s of chick embryos in ovo. The amounts remaining in the eye varied sig nificantly less with the disposable syringes. Leakage into the surroun ding eye-muscles after intraocular injection was significantly more fr equent with Hamilton syringes than with the disposable syringes. Thus, disposable syringes can be a reliable and cost-effective alternative for drug delivery of 2-15 pi volumes. (C) 1998 Elsevier Science B.V. A ll rights reserved.