Researchers have developed a contact lens that can capture and detect exosomes, nanometer-sized vesicles prevalent in human fluids that have the potential to be clinical cancer biomarkers.
The study and findings, led by the Terasaki Institute for Biomedical Innovation (TIBI), were published in the journal Advanced Functional Materials.
The lens was designed with antibody-bound microchambers that can capture the exosomes found in tears. This antibody-conjugated signaling microchamber contact lens (ACSM-CL) can be stained for detection with a nanoparticle-tagged specific antibody for selective visualization. It offers a potential platform for cancer pre-screening and an adjunctive diagnostic tool that is easy, rapid, sensitive, cost-effective and non-invasive.
Exosomes are formed within most cells and are secreted into many bodily fluids, such as plasma, saliva, urine, and tears. Once considered a dumping ground for unwanted substances from their parent cells, it is now known that exosomes can carry various biomolecules between cells. It has also been shown that exosomes contain a wealth of surface proteins – some that are common to all exosomes and others that increase in response to cancer, viral infection or injury. Furthermore, tumor-derived exosomes can strongly influence tumor regulation, progression and metastasis.
Because of these capabilities, there has been great interest in using exosomes for cancer diagnosis and prediction/treatment of prognosis. However, this has been hampered by the difficulty of isolating exosomes in sufficient quantity and purity for this purpose. Current methods include tedious and time-consuming ultracentrifuges and density gradients, which take at least ten hours to complete. Further difficulties arise in the detection of isolated exosomes; Commonly used methods require expensive and space-consuming equipment.
The TIBI team has leveraged their expertise in contact lens biosensor design and manufacturing to eliminate the need for these isolation methods to design their ACSM-CL for capturing exosomes from tears, which are present in blood, urine and An optimal and cleaner source of exosomes than saliva.
They also facilitated and optimized the preparation of their ACSM-CL using alternative methods. When creating the microchamber for their lens, the team used a direct laser cutting and engraving approach instead of traditional cast molding for structural retention of both the chambers and the lens.
In addition, the team introduced a method that chemically modified microchamber surfaces to activate them for antibody binding. This method was used in place of standard approaches, which must use metal or nanocarbon materials in an expensive clean-up setting.
The team then optimized the procedures for binding a capture antibody to the ACSM-Cl microchambers and allowing a different (positive control) detection antibody to be observed spectroscopically on the gold nanoparticles. Both of these antibodies are specific for two different surface markers found on all exosomes.
In a preliminary validation experiment, 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 changes observed in all test samples, compared to negative controls. Similar results were obtained when ACSM-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 ACSM-CL, along with different combinations of marker-specific detection antibodies. . The resulting patterns of detection and non-detection of exosomes from three different cell lines were as expected, thus validating the ability of ACSM-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 many biomedical applications,” said Ali Khademhosaini, PhD, director and CEO of TIBI. “The methodology our team has developed greatly facilitates our ability to tap into this source.”