In many ways, sensors make up the heart of Bioprocessing 4.0. So, an international team of scientists—with members from Australia, China, and the United States—developed what they described as an “extraordinary optical transmission fibre-optic surface plasmon resonance biosensing platform…to monitor the concentrations of monoclonal antibodies.”

As explained by corresponding author Hu Zhang, PhD, professor in bioprocessing at the Keck Graduate Institute in Claremont, CA, surface plasmon resonance (SPR) “is the resonant oscillation of conduction electrons at the interface between a gold film—around 100 nanometers thick—and a glass substrate.” Here, the scientists made a useful modification: developing this sensor from “surface plasmon confined around nano-sized holes across the gold film, enabling higher sensitivity and higher flexibility to excite localized SPR,” Zhang stated. With this approach, the scientists made “a fiber-tip SPR sensor by integrating the nanohole gold film into the enface of a fiber with its diameter similar with a hair size,” according to Zhang.

Although Zhang mentioned that ELISA or HPLC provide the most effective measurements of monoclonal antibodies, he added that this requires taking a sample from a bioreactor and labeling it with enzymes or dyes. “These methods are time-consuming, and the treatment of the cell-culture media may cause loss of the monoclonal antibodies,” he explained.

Fibre-Optic Surface Plasmon Resonance Biosensor [Hu Zhang, PhD, professor, bioprocessing, Keck Graduate Institute

With antibody-antigen binding, this new biosensor detects proteins, including monoclonal antibodies, without treating a sample. “The small size of this sensor makes it ideal for point-of-care or on-site applications with much lower costs compared to current commercial SPR instruments,” Zhang noted. Plus, he pointed out that this biosensor “can detect biomolecules at nanogram or even picogram per milliliter concentrations, and it is not susceptible to external interference.”

The biosensor’s fiber tip allows inline or at-line monitoring. “The measurement takes less than two minutes,” pointed out Zhang. So, this device “provides timely data to be used for optimization of the bioprocess.”

In describing the overall benefits of this device, Zhang said: “The biosensor can be easily delivered to the customer’s location, it’s simple to set up, and it’s applicable to space-limited and remoted locations.”