Biology subjects

Bekdemir, A.

Publications and source records attributed to Bekdemir, A..

3 recordsLinked to original sources

bioRxiv2023

A nanoparticle priming agent reduces cellular uptake of cell-free DNA and enhances the sensitivity of liquid biopsies

Liquid biopsies are enabling minimally invasive monitoring and molecular profiling of diseases across medicine, but their sensitivity remains limited by the scarcity of cell-free DNA (cfDNA) in blood. Here, we report an intravenous priming agent that is given prior to a blood draw to increase the abundance of cfDNA in circulation. Our priming agent consists of nanoparticles that act on the cells responsible for cfDNA clearance to slow down cfDNA uptake. In tumor-bearing mice, this agent increases the recovery of circulating tumor DNA (ctDNA) by up to 60-fold and improves the sensitivity of a ctDNA diagnostic assay from 0% to 75% at low tumor burden. We envision that this priming approach will significantly improve the performance of liquid biopsies across a wide range of clinical applications in oncology and beyond.

genomics↗

bioRxiv2020

Activatable zymography probes enable in situ localization of protease dysregulation in cancer

Recent years have seen the emergence of conditionally activated diagnostics and therapeutics that leverage protease-cleavable peptide linkers to enhance their specificity for cancer. However, due to a lack of methods to measure and localize protease activity directly within the tissue microenvironment, the design of protease-activated agents has been necessarily empirical, yielding suboptimal results when translated to patients. To address the need for spatially resolve d protease activity profiling in cancer, we developed a new class of in situ probes that can be applied to fresh-frozen tissue sections in a manner analogous to immunofluorescence staining. These activatable zymography probes (AZPs) detected dysregulated protease activity in human prostate cancer biopsy samples, enabling disease classification. We then leveraged AZPs within a generalizable framework to design conditional cancer diagnostics and therapeutics, and demonstrated the power of this approach in the Hi-Myc mouse model of prostate cancer, which models features of early pathogenesis. Multiplexed screening against barcoded substrates yielded a peptide, S16, that was robustly and specifically cleaved by tumor-associated metalloproteinases in the Hi-Myc model. In situ labeling with an AZP incorporating S16 revealed a potential role of metalloproteinase dysregulation in proliferative, pre-malignant Hi-Myc prostatic glands. Last, we incorporated S16 into an in vivo imaging probe that, after systemic administration, perfectly classified diseased and healthy prostates, supporting the relevance of ex vivo activity assays to in vivo translation. We envision AZPs will enable new insights into the biology of protease dysregulation in cancer and accelerate the development of conditional diagnostics and therapeutics for multiple cancer types.

bioengineering↗

bioRxiv2019

Reproducibility warning: The curious case of Polyethylene glycol 6000 and spheroid cell culture

In this study we report about the reproducibility of three-dimensional cell culture of floating cell spheroids on PEG6000 treated cell culture dishes. Three-dimensional tumour spheroids or organoids present an interesting test platform for nanoparticulated drug delivery or nanoparticle toxicity. We tested the reproducibility of spheroid formation induced by the PEG coated surface. Interestingly we found that the results were different in a reproducible manner depending on the distributors of PEG6000.\n\nDespite the nearly identical physicochemical properties of PEG6000 (MALDI-MS, NMR, FTIR, Triple SEC) with only minor differences, we observed only for one PEG6000 a highly reproducible formation of spheroids with different cell lines such as HT-29, HeLa, Caco2, and PANC-1. The surface coating with the different PEG6000 was studied by AFM. The surface coating as well as the physicochemical characterization showed only small differences in mass and hydrodynamic radius between the different PEGs. A direct coating of the cells with PEG from two distributors indicate that the spheroid formation in due to direct interaction of the polymer with the cell rather than by interaction of cells with the coated surface.\n\nThe experiments point out that for biological entities, such as cells or tissues, even very small differences such as impurities or batch-to-batch variations in the purchased product can have a very strong impact.

scientific communication and education↗