Lateral Flow Strip

A sandwich format produces a test signal when the target is captured between two recognition reagents, making it suitable for detecting target molecules through paired binding interactions. In a competitive format, sample target competes with a labeled or immobilized target-related component for recognition. The resulting signal therefore reflects different relationships between target concentration and test-line intensity.

Each strip component supports a different stage of analysis. The conjugate pad holds labeled antibodies, aptamers, or other affinity reagents before sample contact. The porous membrane provides the surface for capture at the test line, while the control line indicates that liquid has migrated through the device and that the flow process functioned properly.

Antibodies, aptamers, and other affinity reagents provide the molecular recognition step that gives a strip its target selectivity. Their binding interactions can be directed toward proteins, hormones, nucleic acids, metabolites, or pathogens. Choosing the appropriate reagent and assay format connects the biochemical identity of the target with the visible signal generated on the membrane.

Interpretation depends on both lines rather than the test line alone. A visible control line supports that sample movement occurred through the strip, whereas the test line reports target-related binding according to the selected sandwich or competitive design. If the control response is absent, the result does not demonstrate a valid assay process, regardless of the test-line appearance.

A typical workflow introduces a liquid sample to the strip, allows capillary movement across the conjugate pad and membrane, and then examines the test and control regions. During migration, labeled recognition reagents interact with targets and may be captured at the test line. The resulting line pattern provides a rapid visual outcome without requiring specialized laboratory equipment.

These devices are useful when testing must be portable, rapid, low-cost, and accessible outside a specialized laboratory. Their applications include point-of-care diagnostics, environmental monitoring, food safety, and research assays. In biochemistry, they can extend detection of molecular targets such as proteins, hormones, nucleic acids, metabolites, and pathogens to decentralized testing settings.