Carterra’s patented flow printing technology was invented in the lab of Prof. Bruce Gale at the University of Utah Department of Mechanical Engineering and uses a network of microchannels that uniquely enable flow-based array printing of proteins and antibodies on sensor surfaces. In contrast to spotter and printer technologies that use fixed volume droplets with uncertainty in binding coverage, flow printing uses micro-channels to flow and cycle ligand solutions over a defined surface area. This maintains sensitive proteins in a liquid environment throughout the immobilization step and produces highly defined active spots with coverage that approaches saturation.
Surface Plasmon Resonance (SPR) platforms typically use a unidirectional flow system that limits both association and dissociation times which impose restrictions on kinetic studies and increase sample usage. By turning the orientation of the flow cell through 90°, flow printing enables the same flow characteristics required for high quality kinetics studies, but with significant benefits in terms of fluidic performance and SPR data output, thereby expanding applications.
The 96-Channel Printhead enables a 96 protein array to be immobilized in parallel from flow onto a sensor chip surface in a single step. Sample is taken from either a 96 well plate or one quadrant of a 384 well plate and cycled through the 96 Printhead which is docked onto the surface of an SPR chip. Each of the 96 printhead channels creates a fluidically isolated flow cell on the surface of the chip, enabling flow-based immobilization for 96 distinct samples simultaneously. This can be repeated up to 4 times to build a 384 array on the SPR surface, all with real-time SPR detection throughout the assay, from surface preparation through to kinetic interaction.
The LSA’s Single Flow Cell (SFC) utilizes a single needle and dual syringe pumps to deliver high-quality flow across the chip surface via a proprietary fluidics cartridge. The SFC cartridge automatically switches with the printhead to cover the entire chip surface as needed, for surface preparation, regeneration, and delivery of one sample to address all spots created on the surface by the 96 Printhead.
The LSA seamlessly integrated both single flow cell and 96-channel printhead switching.
The LSA utilizes a laser diode light source to illuminate the functionalized gold surface at the interface with the prism and reflected light is detected via a high-resolution CCD camera. At the boundary of the functionalized gold layer and the glass prism a certain fraction of incident light photons propagates as surface plasmons, forming an evanescent field which is sensitive to changes in refractive index (RI) at the functionalized surface. When the RI changes, such as when molecules bind, the angle of incident photon absorption shifts and this change in the minima of reflected light is used to quantify binding.
While the CCD camera in the LSA can monitor the entire SFC area, data collection is focused on locations by using flow printing technology (up to 384), as well as unprinted locations typically used as references (48), totaling 432 spots, over which a single analyte is then flowed.
LSA sensor chips consist of a functionalized gold wafer adhered to a dove-cut glass prism, forming an SPR coupler capable of eliciting the SPR phenomenon. Within the LSA, the sensor chip is docked in the path of the optics module allowing incident light to interact with this SPR coupler, while a portion exits as reflected light to the detector.