Abstract: Materials and method are disclose for delivering a desired substance to a target site, using a layered carrier in which the carrier and the substance together form at least three layers which associate by ionic interaction at the first pH, where at least one layer comprises a charge switch material which comprises an ionisable group and which has a positive charge at a first pH and a charge which is less positive, neutral or negative at a second pH, at least one layer comprises a polyionic polymer which is negatively charged at the first pH and at least one layer comprises the desired substance. Preferred carriers are based on the charge switch material poly Bis-Tris and the polyionic polymer polyacrylic acid.

Abstract: An evacuated blood collection assembly includes a plastic container having a plasma-treated inside wall surface and an open end covered by a puncturable septum. The inside wall surface may also be abraded to increase surface area. The invention included a method to make the assembly.

Abstract: A blood collection container is coated on its inside wall with a unitarily immobilized clotting activator. The activator may be applied to the surface by an adhesive or by rendering the inside wall surface sticky with a solvent and partially absorbing the activator into the sticky surface.

Abstract: An additive for a blood collection container is a polyelectrolyte complex having a surface charge which activates clotting of a blood sample in the container. A preferred additive is a crosslinked carboxylated cellulose having a negative charge. The invention includes a blood collection tube having a puncturable stopper in an open end and the additive of the invention deployed therein.

Abstract: A glass or plastic article, preferably a blood collection tube, has two or more surface regions of different surface chemistry. One region is substantially glass-like and another region is substantially plastic-like. If the tube is glass, a region of the tube adjacent the tube bottom is plastic-like. If the tube is plastic, a region of the tube adjacent the mouth of the tube is be glass-like.

Abstract: An additive for a blood collection tube has a wettable surface region and a nonwettable surface region. When a blood sample comes into contact with the wettable surface region, the clotting cascade is initiated. Clot material adheres to the nonwettable surface region. The additive thereby becomes part of the clot and, on centrifugation, becomes part of the pellet and is removed from the serum layer. The invention includes a blood collection tube having the additive therein. The tube may be evacuated and have an open end covered with a septum.