## 1 Introduction  
Concanavalin A (Con A) was first identified by [PERSON] and [PERSON] in 1935 [1] and is a carbohydrate binding protein (lectin) that is extracted from the jack bean (_Canavalia ensiformis_). Lectins are storage proteins thought to form part of the passive defence systems of plants by exhibiting specific binding affinities to animal glycoproteins and thereby provoking a toxic response [2]. The lectin Con A binds specifically by hydrogen bonds to the 3 rd, 4 th and 6 th carbon of the pyranosyl ring system of \(\alpha\)-mannosyl, \(\alpha\)-glycosyl and \(\alpha\)-N-acetylglucosamineamy! groups acting as the non-reducing termini of mono and polysaccharides [3]. This interaction has been exploited in various biological applications for example cell separation [4], immobilisation of micro-organisms [5], glycoenzyme separation [6], identification of carbohydrates [7], mapping of glycoconjugates [8] and the detection of viruses [9]. The specificity of Con A binding towards a selected group of carbohydrates have also been explored in biosensor applications, in which the lectin was incorporated as the primary ligand in the detection of biologically active metabolites. It is especially the binding affinity of the \(\alpha\)-glycosyl group of glucose and dextran that have raised interest for use in glucose sensors based on the competitive binding between these two in their interaction with Con A [10; 11; 12; 13]. Despite traditional enzyme sensors representing the state-of-the-art in glucose monitoring [14], they suffer from a degradation in enzyme activity [15], interfering electroactive compounds [16], changing hematocrit level [17], electrode fouling [18] and the requirement of mass transport control [19]. Although remedies have been sought to rectify parts of these challenges [20; 21], lectin based sensors have the potential to bypass the drawbacks posed from the combination of enzymes with an electrochemical system. Work on non-enzymatic glucose sensors have explored the use of functionalised receptors made from carbon nanotubes [22], nanomaterials with enzyme like behaviour [23] and abiotic catalysts [24]. Inactive enzymes (e.g., apo-glucose oxidase) have been used as affinity receptors in \"smart tattoos\"-small capsules of glucose sensitive hydrogels that emit a shift in photoluminescence [25] as a function of glucose concentration, or in conjunction with gold nanoparticle probes that emit light through fluorescence resonance energy transfer [26]. However, non-enzymatic glucose sensors, smart tattoos and gold nanoprobes, are still at the proof of concept level and have not attained widespread commercial use. A lectin-based sensor would require a transducer mechanism that conveys the signal by physical or optical means. One potent application permits the registration of small changes in mass or viscoelasticity associated with the binding of molecular species on a surface [27]. This form for gravimetric detection permits label free measurements of glucose to be performed without the use of any fluorophores. Moreover, the competitive binding between the smaller glucose (180 Da) and the larger dextran molecule (3-70 kDa) with Con A amplify the mass change on the surface making the accompanying change in the resonance frequency more easily detectable [28]. This change in resonance frequency can be monitored by quartz crystal microbalances (QCM) [12], acoustic Love wave (LW) resonators [29] or thin film bulk acoustic resonators (FBAR) [27]. These gravimetric sensors share a common trait of using silicon oxide based ceramics (silica, silicon dioxide, quartz) as their bulk and/or surface material, as well as the guiding layer modulating the entrapment and propagation of acoustic waves in LW devices. It is on this surface material that one of the components of the Con A affinity assay would need to be immobilised. Immobilisation strategies described in prior art focus on immobilising dextran to the sensor surface with Con A and glucose being freely suspended in the surrounding solution [10; 11; 12; 28].