Researchers have developed a contact lens that can capture and identify exosomes, nanometer-sized vesicles found in human fluids that have the potential to be diagnostic cancer biomarkers.
The study led by Terasaki Institute for Biomedical Innovation (TIBI) and its findings were published in the journal Advanced Functional Materials.
The lens is designed with microchambers bound to antibodies that can capture exosomes found in tears. This antibody-conjugated signaling microchamber contact lens (ACSM-CL) can be stained for detection with specific nanoparticle-tagged antibodies for selective visualization. This provides a potential platform for cancer pre-screening and a supportive diagnostic tool that is convenient, rapid, sensitive, cost-effective and non-invasive.
Exosomes are formed in most cells and secreted into many body fluids, such as plasma, saliva, urine, and tears. Once thought to be the dumping ground for unwanted materials from their cells of origin, it is now known that exosomes can transport various biomolecules between cells. There is also a wealth of surface proteins on exosomes shown – some common to all exosomes and others that increase in response to cancer, viral infections or injury. In addition, exosomes derived from tumors can strongly influence tumor regulation, progression and metastasis.
Because of these capabilities, there has been considerable interest in the use of exosomes for cancer diagnosis and prognosis/treatment prediction. However, this was 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, which take at least ten hours to complete. Further problems arise in the detection of the isolated exosomes; common methods require expensive and space-consuming equipment.
The TIBI team has used their expertise in the design and manufacture of contact lens biosensors to eliminate the need for these isolation methods by developing their ACSM-CL for trapping exosomes from tears, an optimal and cleaner source of exosomes than blood, urine and saliva.
They also facilitated and optimized the preparation of their ACSM-CL by using alternative approaches. When fabricating the microchambers for their lens, the team used a direct laser cutting and engraving approach rather than conventional casting for structural retention of both the chambers and lens.
In addition, the team introduced a method that chemically modified the microchamber surfaces to activate them for antibody binding. This method was used instead of standard approaches, which require the use of metals or nanocarbon materials in expensive cleanroom environments.
The team then optimized procedures for binding a capture antibody to the ACSM-CL microchambers and another (positive control) detection antibody to gold nanoparticles that can be visualized spectroscopically. Both antibodies are specific for two different surface markers found on all exosomes.
In a first validation experiment, the ACSM-CL was tested against exosomes secreted 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 test samples, compared to the negative controls. Similar results were obtained when the ACSM-CL was tested with ten different tear samples collected from volunteers.
In final experiments, exosomes in supernatants collected from three different cell lines with different surface marker expressions were tested against the ACSM-CL, along with 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, validating the ability of the ACSM-CL to accurately capture and detect exosomes with different surface markers.
“Exosomes are a rich source of markers and biomolecules that can be used for a variety of biomedical applications,” said Ali Khademhosseini, Ph.D., director and CEO of TIBI. “The methodology our team has developed makes it significantly easier for us to tap into this resource.”