Objective

Surface Plasmon Resonance is a biophysical surface technique that is widely applied in screening of small molecules and biologicals in drug discovery process. Identification and validation of hits is a crucial element in development of new drug molecules and SPR enables a high-throughput screening in real time and label-free manner. Traditional SPR set-up provides affinity and kinetics information on molecule binding to their biomolecular targets but is limited to studies within a layer of 150nm. Therefore, we hereby propose a recently developed SPR configuration, namely Multi-Parametric SPR which overcomes such limitation. Indeed, our technique combines wide angular scanning and multiple wavelengths under SPR optical set-up thus enabling measurements within layers from Ã…ngströms up to tens of microns on the sensor surface.  Therefore, MP-SPR not only can address binding of small molecules to their biological targets i.e. proteins but also opens to direct assessment of biological layers including vesicles, living cells and tissues.

In a study by Viitala et al., the MP-SPR platform was applied to directly measure interactions of small drugs with living cells cultured on the sensor chip. A monolayer of model MDCKII cells was generated over gold surface of the SPR sensor and subsequently exposed to two molecules: propranolol and D-mannitol. The MP-SPR measurements confirmed both drugs to be passively absorbed by cells and enabled to distinguish two independent drug behaviour: propranolol was absorbed using transcellular whereas D-mannitol paracellular route of absorption.  In their work, Suutari et al. addressed uptake of nanoparticles (NPs) of different type by HeLa cells grown on the SPR sensor.  Model potential nanotherapeutics (PEI-DNA polyplexes, extracellular vesicles and silica NPs) were introduced onto the chip and the MP-SPR measurements evidenced substantial differences in their uptake by cells. In both aforementioned examples, assessment of interactions with living cells was performed in real time and without labelling.

Apart from studies on live cells, the unique configuration of MP-SPR systems enables measurements of crude samples e.g. 100% serum which can’t be performed with traditional SPR systems. Kari et al. used our multi-parametric approach to assess interactions between liposomes containing Doxil and samples of 100% human serum. The study brought detailed insight into the formation of protein corona which is an essential information in development of nanomedicines. Moreover, MP-SPR resulted to be compatible with un-purified samples issued from production of biopharmaceuticals. Affinity constants for binding of biosimilar adalimumab to human Fc receptors (CD23b and CD16) were obtained from crude samples containing both antibodies and cells used in bioprocess.

MP-SPR is a versatile technique that goes beyond traditional application of the SPR approach limited to drug screening and hit identification. Here presented examples show that our platform can directly address biological targets i.e. live cells involved in a disease setting and confirm its compatibility with complex biological samples. The unique features offered by the MP-SPR can furthermore increase the pace of new drug development and support the drug discovery chain.