Technetium-99m labeling of albumin microspheres intended for drug targeting

In vivo evaluation of dosage forms: application of gamma scintigraphy to non-enteral routes of administration

The trend to deliver drugs to defined areas of the body involves sophisticated carriers systems. In addition to the in vitro drug release profile one must be aware of the in vivo behaviour of the dosage form and the drug. Gamma scintigraphy is an elegant way to gain insights of the actual in vivo distribution pattern of dosage forms. This technique relies on the use of radioactive tracers included into the medicament and selected so as to enable an optimum detection by a gamma ray camera. The choice of a convenient label enables the in vivo determination of the targeting of the formulation administered through a large number of routes. The present paper reviews applications of gamma scintigraphy for the evaluation of dosage forms administered by the parenteral, rectal, buccal, nasal, pulmonary, and ophthalmic routes.

Studies of quality control of 99mTc-labelled macroaggregated albumin--Part 1. Aggregation of non-mercaptalbumin and its conformation

The aggregative condition of albumin was investigated using bovine serum albumin (BSA) as a model for quality control of 99mTc-macroaggregated albumin (99mTc-MAA). Uniformalized aggregates were obtained from the oxidized non-mercapt-type of BSA by heating. The size of the aggregates was affected by the pH and the types of buffer solutions used as well as the concentrations of albumin and buffers. The beta form structure of the albumin was more stable on heating and this may contribute to its aggregation. Aggregation of oxidized non-mercaptalbumin afforded a portion of smaller sized particles in MAA, this being an inappropriate factor for scintiscanning of lungs. Our results suggest that it is necessary to remove oxidized type albumin from human serum albumin as the starting material, in order to prepare MAA with a uniform and larger particle size.

Microspheres for biomedical applications: preparation of reactive and labelled microspheres

This review describes the synthesis and physico-chemical properties of reactive and labelled microspheres useful for biomedical applications. Preparation of microspheres with specific functional groups, fluorescent species, radionuclides and magnetite particles (Fe2O3) are discussed. Physico-chemical properties of microspheres, including surface charge and hydrophilicity/hydrophobicity, are also briefly covered.

Albumin microspheres. I: Physico-chemical characteristics

Albumin microspheres are biodegradable particles which can be readily radiolabelled and synthesized in the size range of 1 to 200 microns. During the last 30 years extensive efforts have been made towards the design and development of this carrier for the purpose of diagnosis and drug delivery. This review presents a thorough discussion on the physico-chemical characteristics of albumin microspheres.