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High Conjugation Efficiency CdPbS Near-infrared Molecular Probe

Friday, November 11, 2022

3:00 PM-5:00 PM

BIOMED PhD Thesis Defense

High Conjugation Efficiency CdPbS Near-infrared Molecular Probe Toward Intraoperative Breast Cancer Margin Assessment
Alexandra (Lexi) Jednorski, PhD Candidate
School of Biomedical Engineering, Science and Health Systems
Drexel University
Wan Shih, PhD
School of Biomedical Engineering, Science and Health Systems
Drexel University

Wei-Heng Shih, PhD
Department of Materials Science and Engineering
College of Engineering
Drexel University

Breast cancer makes up a large fraction of newly diagnosed cancer cases in the US. About 42% of breast cancer patients choose to undergo a lumpectomy or breast-conserving surgery (BCS) as opposed to mastectomy. Around 25% of the time, a re-excision surgery must be performed to remove more breast tissue as breast cancer margins were found to be positive post-BCS. There is a need for a rapid and specific intraoperative breast cancer margin assessment technique, so margins can be assessed during surgery reducing the incidence of re-excision surgeries.

A molecular probe consisting of a near-infrared (NIR) emitting aqueous quantum dot (AQD) conjugated to a cancer-specific antigen antibody (Ab) was developed for direct immunofluorescence staining of breast cancer tissues. Quantum dots (QDs) are semiconducting nanocrystals. They possess superior optical qualities to traditional organic dye fluorophores used in immunofluorescence imaging including increased photostability and tunable excitation and emission wavelengths. Specifically, CdPbS AQDs were applied to the molecular probe design as they emit NIR light that is well-separated from any tissue autofluorescence. They have a facile aqueous synthesis without the need for phase transfer; however, they become unstable in biological conditions like neutral buffers. Therefore, before conjugation to the Ab, the AQD surface was modified by replacing its original capping-molecule with dihydrolipoic acid (DHLA). This method rendered a highly stable AQD ready for conjugation to Ab in a neutral environment.

The molecular probe utilized polyethylene glycol (PEG) to act as a spacer between DHLA-replaced AQD and Ab. This allowed for multiple AQDs to bind per Ab, something not found in literature on direct staining. The molecular probe design was developed using cell lines before its application to human breast tissue slices. It had a repeatable signal-to-noise ratio of 25-30. In formalin fixed paraffin embedded human breast tissues, it showed sensitivity and specificity of over 95% for the Tn antigen, specific to carcinomas. A professional pathologist deemed the tissue staining results promising. A more diverse set of breast tissue cases should be stained in the future for a greater understanding of the molecular probe’s application to various breast pathologies before its application to freshly excised breast tissues. At that stage, a custom imaging setup can be utilized for macroscopic tissue imaging. The imaging system was tailored to the properties of the AQD fluorescence and evenly illuminates an area large enough for most tumor sizes. Overall, a NIR molecular probe with multiple AQDs per Ab was designed for direct imaging of breast cancer tissues with promise for future applications in intraoperative imaging of fresh tissue specimens.

Contact Information

Natalia Broz

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