In 1985, George Smith introduced phage display, a groundbreaking technique for presenting peptides fused to the bacteriophage coat protein pIII (Smith, 1985; Smith and Petrenko, 1997). This method enables the display of large libraries of diverse peptides, with each phage particle ideally presenting a unique sequence (Devlin et al., 1990; Laman et al., 2020; Parmley and Smith, 1988; Scott and Smith, 1990; Zhao et al., 2023). Although some level of sequence redundancy is inherent, the sheer number of phage particles generated reflects a vast sequence diversity, often of billions of variants (Sinkjaer et al., 2025). This technology was later adapted to display larger polypeptides, including antibodies, marking the beginning of recombinant monoclonal antibody technology (Barbas et al., 1991; Breitling et al., 1991; Clackson et al., 1991; Hoogenboom et al., 1991; Lee et al., 2024; McCafferty et al., 1990). By integrating recombinant DNA technology with phage display, researchers could now identify monoclonal antibodies without the use of animals (Bradbury and Marks, 2004; Willats, 2002).

The fundamental concept of antibody display is to isolate high-affinity antibody clones from large libraries based on their binding strength and specificity to a target antigen (Barbas 3rd et al., 1991; Breitling et al., 1991; McCafferty et al., 1990; Winter et al., 1994). This principle governs selection across various display platforms (Porebski et al., 2024; Slavny et al., 2024). A key characteristic of phage display, and other related systems, is the genotype–phenotype linkage, i.e. the direct association between the antibody gene sequence and the expressed antibody protein (Jaroszewicz et al., 2022; Mustafa and Mohammed, 2024). This physical bridge enables accurate identification of specific antibody clones (Jaroszewicz et al., 2022; Mustafa and Mohammed, 2024; Watanabe et al., 2024). Early phage display systems were limited to moderately sized peptides due to constraints on phage size/function and the challenges of displaying larger proteins (Zhang, 2023). Recent studies have shown that full-length antibodies can now be displayed on phage, however only limited numbers of functional full-length displayed antibodies have been demonstrated and diverse libraries are yet to be reported (Zhang et al., 2021a, Zhang et al., 2021b; Zhou et al., 2010). More commonly, a variety of smaller recombinant antibody formats such as single fragment variable (scFv), Fragment antigen binding (Fab), single-domain antibodies (VHH) that subsequently allow for conversion to full-length antibodies after selection have been developed for phage display (Dyson et al., 2020; Kirsch et al., 2005; Ledsgaard et al., 2018). These same formats are also used in other display technologies, including ribosome, yeast, bacterial, and mammalian cell display (Doerner et al., 2014).

Just as the immune system relies on a diverse repertoire of antibodies to target specific infections, antibody display technologies enable the selection of high-affinity clones from vast in vitro libraries (Lai and Lim, 2020). This selection is based on the affinity of antibodies for a target antigen (Winter et al., 1994). Such in vitro antibody libraries are fundamental to display technologies. This review explores common recombinant antibody formats, various antibody library types, and diverse display technologies used to present antibodies. Furthermore, it examines how recombinant antibodies are applied in a variety of diagnostic platforms. The shift towards recombinant antibodies represents a Midas touch for the diagnostic industry, where the ability to customize antibodies at the genetic level allows for the development of diagnostic platforms with unprecedented specificity and scalability required for next generation point of care testing.