Molecular Imprints for the Detection of Specific Glycoproteins Implicated in Cancer

Molecular diagnostics rely heavily on immuno-detection, such as the enzyme-linked immunosorbent assay (ELISA).1 One of the key drawbacks of employing antibodies in biomedical detection systems is their inability to... [ view full abstract ]

Molecular diagnostics rely heavily on immuno-detection, such as the enzyme-linked immunosorbent assay (ELISA).1 One of the key drawbacks of employing antibodies in biomedical detection systems is their inability to differentiate between different glycoforms of the same protein.2 3 One such ELISA, where this short-coming is pronounced is the prostate specific antigen (PSA) ELISA developed for the diagnosis prostate cancer.4 There are multiple glycoforms of PSA including those that are strongly suggested as biomarkers of prostate cancer, however the ELISA, which is considered the ‘gold standard, cannot distinguish between normal and cancerous glycoforms making the test uninformative, unreliable and inaccurate.5 6 To this end, we look to utilise molecular imprinted polymers (MIPs) to produce a novel diagnostic method for the detection of cancerous PSA glycoforms.

MIPs within ultra-thin hydrogels are synthesised from a surface using controlled living polymerisation (Figure 1). An initiator molecule (11’-dithiobis[1-(2-bromo-2-methylpropionyloxy)undecane]) is synthesised and incubated with gold to form a self-assembled monolayer (SAM). In a separate step, PSA is incubated with vinyl-boronic acid to form a complex. The complex is then incubated with the initiator surface and polymerisation triggered around the complex using N,N’-methylenebisacrylamide (MEBA), Cu(I)Br and 2,2’-bipyridine as the metal-ligand catalyst and ethyl-2-bromoisobutyrate as a sacrificial initiator to form an imprint in biologically compatible conditions.

The afforded SAMs were in good agreement with the literature, measuring 1.74 ± 0.12 nm in thickness and with a water advancing angle of 70 ± 1.8°, as evaluated by ellipsometry and contact angle, respectively.7 The extent of the polymer network was determined by the ratio of Cu(I)Br to Cu(II)Br. The resultant system was then optimised to produce MEBA layers with a thickness of 8.07 ± 0.76 nm, which will act as the foundation into which PSA imprints will be formed. We now look to incorporate boronic acid monomers complexed with PSA into the polymerisation network to create MIPs capable of differentiating between the subtle differences in the glycosylation characteristic of each PSA glycoform, to thus produce an informative, reliable and accurate test for prostate cancer.