A photoimmobilization technique for decorating surfaces with micropatterns that consist of variable densities of bioactive molecules is described. The efficacy of the patterns for controlling cell adhesion and shape has been demonstrated. This technique is useful for the study of cell behavior on micropatterns.

Gradients of biological molecules on a microscale have been postulated to elicit cellular responses, such as migration. However, it has been difficult to prepare such gradients for experimental testing. A means for producing such gradients has been developed using a heterobifunctional photolinking agent with laser light activation. The photolinking agent synthesized includes an N-hydroxysuccinimide group and a photoreactive benzophenone (BP) separated by a tetraethylene glycol (TEG) spacer. The presence of the tetraethylene glycol spacer renders the photolinker hydrophilic, a desirable trait for conjugation in aqueous solutions. The linker was then conjugated to R-phycoerythrin (R-PE), a fluorescent protein. The resulting photolinker-R-phycoerythrin conjugate (BP-TEG-PE) was then immobilized onto a polystyrene surface by laser irradiation on a motorized stage. By varying exposure time of the sample to the beam, the amount of BP-TEG-PE immobilized on the surface was changed over an order of magnitude over a distance of 250 microns. This method can be applied to prepare gradients of proteins that elicit biological responses, such as extracellular matrix proteins or growth factors, and to study the biological effects of such gradients.

A new homogeneous chemiluminescent immunoassay method featuring the use of specific binding members separately labeled with an acridan-based chemiluminescent compound and a peroxidase is reported. Formation of an immunocomplex brings the chemiluminescent compound and the peroxidase into close proximity. Without any separation steps, a chemiluminescent signal is generated upon addition of a trigger solution, and the intensity is directly correlated to the quantity of the analyte.