Scientists from the Terasaki Institute for Biomedical Innovation (TIBI) have developed a contact lens capable of capturing and detecting exosomes, nano-sized vesicles found in bodily secretions that have the potential to be diagnostic biomarkers for cancer. The lens was designed with microchambers linked to antibodies that can capture exomes found in tears.
This Antibody Conjugated Signaling Microchamber Contact Lens (ABSM-CL) can be colored for detection with specific nanoparticle labeled antibodies for selective visualization. This offers a potential platform for cancer pre-screening and a simple, rapid, sensitive, cost-effective, and non-invasive supportive diagnostic tool.
Exosomes are formed in most cells and secreted into many body fluids, such as plasma, saliva, urine, and tears. Once thought of as dumping grounds for unwanted materials from their cells of origin, it is now known that exosomes can transport different biomolecules between cells. It has also been shown that there are a multitude of surface proteins on exosomes – some that are common to all exosomes and others that are increased in response to cancer, viral infections or injury. Moreover, tumor-derived exosomes can strongly influence tumor regulation, progression, and metastasis.
Because of these capabilities, the use of exosomes for cancer diagnosis and prognosis/treatment prediction has garnered much interest. However, this has been hampered by the difficulty of isolating exosomes in sufficient quantity and purity for this purpose. Current methods involve tedious and time-consuming ultracentrifuge and density gradients, lasting at least ten hours. Other difficulties arise in the detection of isolated exosomes; commonly used methods require expensive and bulky equipment.
The TIBI team leveraged their expertise in designing and manufacturing contact lens biosensors to eliminate the need for these isolation methods by designing their ABSM-CL to capture exosomes from tears, a source of exosomes optimal and cleaner than blood, urine and saliva.
They also facilitated and optimized the preparation of their ABSM-CL through the use of alternative approaches. When fabricating the microchambers for their lens, the team used a direct laser cutting and etching approach rather than conventional die casting for the structural retention of the chambers and lens.
Additionally, the team introduced a method that chemically modifies the surfaces of the microchambers to activate them for antibody binding. This method was used instead of standard approaches, in which metallic or nanocarbon materials have to be used in expensive cleanrooms.
The team then optimized procedures to bind a capture antibody to ABSM-CL microchambers and a different detection antibody (positive control) to gold nanoparticles that can be visualized spectroscopically. These two antibodies are specific for two different surface markers present on all exosomes.
In a first validation experiment, ABSM-CL was tested against secreted exosomes in supernatants from ten different tissue and cancer cell lines. The ability to capture and detect exosomes was validated by the spectroscopic shifts observed in all samples tested, compared to negative controls. Similar results were obtained when ABSM-CL was tested against ten different tear samples collected from volunteers.
In the final experiments, exosomes in supernatants collected from three different cell lines with different surface marker expressions were tested against ABSM-CL, as well as different combinations of marker-specific detection antibodies. The resulting patterns of detection and non-detection of exosomes from the three different cell lines were as expected, thus validating the ability of ABSM-CL to accurately capture and detect exosomes with different surface markers.
“Exosomes are a rich source of markers and biomolecules that can be targeted for several biomedical applications,” said Ali Khademhosseini, Ph.D., Director and CEO of TIBI. “The methodology that our team has developed greatly facilitates our ability to tap into this source.”
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