Radio-iodination of neurotrophins and their delivery in vivo: advantages of membrane filtration and the use of disposable syringes

Abstract

This paper reports two simple improvements for the radio-iodination of neurotrophins and their delivery in vivo. (1) Neurotrophins can be effectively separated from free iodide by using membrane filtration devices. Seven methods for the separation of free iodide are compared, including dialysis, gel filtration, and membrane filtration. Membrane filtration of the iodinated protein has several important advantages over dialysis or gel filtration. These include the precise control over the final concentration; excellent recovery of the neurotrophin; easy and inexpensive procedure; performance of the entire procedure in a fume hood; and reduced volume of radioactive waste. (2) Disposable, inexpensive syringes are suitable for the delivery of small volumes of radio-iodinated or non-radioactive neurotrophins. Plastic disposable insulin syringes are compared with Hamilton syringes. The ejection volume of the disposable syringes is surprisingly reliable in the dose range 2–15 μl. Their in vivo performance was tested by injections in the eyes of chick embryos in ovo. The amounts remaining in the eye varied significantly less with the disposable syringes. Leakage into the surrounding eye-muscles after intraocular injection was significantly more frequent 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 μl volumes.