In a recent article published in the journal Sensing and Bio-Sensing Research, researchers developed a label-free optical fiber biosensor for the detection of CD44-expressing breast cancer cells. CD44 is a significant biomarker associated with cancer progression and metastasis, making its detection crucial for early diagnosis and treatment monitoring.
The overview of the experimental setup used for the detection of CD44-expressing cancer cells by optical fiber biosensor (OFB). Zoomed image shows the spherical tip of the ball resonator sensor functionalized with CD44-antibodies capturing target cells. Created using BioRender software (http://biorender.com). Image Credit: https://www.sciencedirect.com/science/article/pii/S2214180424000436
Background
Cancer continues to be a significant global health challenge, and early detection is crucial for effective management. Breast cancer, in particular, stands as one of the most common cancers affecting women worldwide. The identification of specific biomarkers associated with breast cancer, such as CD44, has become a vital strategy for early diagnosis and targeted therapy.
In breast cancer cases, the presence of CD44-expressing cells is often associated with aggressive tumor behavior, metastasis, and resistance to conventional therapies. Thus, the accurate detection and quantification of CD44-expressing cells are essential for effective prognosis, treatment planning, and monitoring of disease progression. This approach can lead to more personalized therapies, improving outcomes and potentially reducing the impact of breast cancer globally.
The Current Study
In this study, the optical fiber biosensor was constructed using a fiber-optic ball resonator (BR) sensor, starting with a thorough cleaning of the single-mode fiber (SMF) using Piranha solution to eliminate contaminants and ensure surface cleanliness. Following the cleaning, the fiber was functionalized with (3-aminopropyl)trimethoxysilane (APTMS) and glutaraldehyde (GA), creating binding sites crucial for the attachment of CD44 antibodies. This step was pivotal for enhancing the biosensor's specificity towards CD44-expressing cells.
Post-functionalization, the biosensor was incubated with CD44 monoclonal antibodies, enabling the specific recognition of the CD44 biomarker found on the surface of breast cancer cells. The immobilization process of the antibodies was optimized to maximize binding efficiency while minimizing non-specific interactions.
To further reduce non-specific binding from non-target molecules, the biosensor surface underwent treatment with methoxy-polyethylene glycol amine (mPEG-amine). This step aimed to block any remaining active sites, thus minimizing background noise during the detection phase.
The prepared biosensor was then exposed to various concentrations of CD44-expressing breast cancer cells, such as HCC1806 cells. The binding of these cells to the immobilized antibodies caused changes in the reflected light intensity, which was detected using an optical backscatter reflectometer. These changes in intensity were directly correlated with the concentration of cancer cells in the sample.
The spectral data collected from the reflectometer were processed and analyzed using MATLAB software. This analysis included quantifying the intensity changes across different cell concentrations and determining the limit of detection (LoD) for CD44-expressing cells. Statistical methods were employed to validate the sensitivity and specificity of the biosensor in identifying the target cells.
Lastly, the reproducibility of the biosensor was assessed through multiple experiments using varying concentrations of cells. This evaluation ensured the consistency of the biosensor's response and its reliability in detecting CD44-expressing cells across different trials, confirming the platform's effectiveness for clinical applications.
Results and Discussion
The optical fiber biosensor demonstrated successful detection of CD44-expressing breast cancer cells, affirming its effectiveness as a sensitive and specific platform for cancer biomarker detection. The biosensor's spectral response exhibited noticeable changes in reflected light intensity corresponding to various concentrations of HCC1806 cells, validating its capability to accurately recognize and interact with CD44 biomarkers on the surface of target cells.
The sensitivity of the biosensor was quantified by calculating the LoD for CD44-expressing cells. This LoD, determined from the observed intensity changes relative to cell concentrations, represented the minimum concentration of target cells detectable by the biosensor. The achieved low LoD underscored the biosensor's high sensitivity, which is crucial for detecting trace amounts of CD44-expressing cancer cells and is pivotal for early cancer detection and ongoing monitoring.
A comprehensive specificity analysis evaluated the biosensor's ability to distinguish CD44-expressing breast cancer cells from other analytes. The sensor's selective response to various analytes, including DPBS and raw data, showcased its capability to specifically detect CD44-expressing cells. The repeatability of the biosensor's performance across multiple trials further confirmed its specificity and reliability in cancer cell detection applications.
Comparatively, the optical fiber biosensor's performance was evaluated against traditional methods like flow cytometry and immunohistochemistry (IHC), which are commonly used for CD44 detection. The advantages of the biosensor, including its label-free detection, quantitative capabilities, and absence of electromagnetic interference, provided distinct benefits over these conventional techniques. This comparison highlighted the biosensor's potential as a rapid, cost-effective alternative for the analysis of cancer cells, thereby enhancing diagnostic and monitoring processes.
Conclusion
This study introduces a novel method for the label-free detection of CD44-expressing breast cancer cells using an optical fiber biosensor. The results affirm the biosensor's high sensitivity and specificity in identifying target cells, underscoring its potential utility in cancer diagnosis and research. The developed biosensor provides a rapid and dependable technique for quantifying CD44 biomarkers, facilitating significant strides in early cancer detection and the advancement of personalized medicine. This approach could revolutionize current diagnostic methodologies, offering more timely and tailored treatment options for patients.
Journal Reference
Marzhan N., Kanagat K., et al. (2024). Label-free optical fiber biosensor for the detection of CD44-expressing breast cancer cells. Sensing and Bio-Sensing Research 44, 100661. DOI: 10.1016/j.sbsr.2024.100661, https://www.sciencedirect.com/science/article/pii/S2214180424000436