Design, synthesis, and conjugation of mesoporous silica nanoparticles (MSNs) with biomolecules is a matter of growing interest to enhance selective uptake of contrast agents like gadolinium (Gd3+) by cancer cells. Here, by targeting xc-cystine/glutamate antiporter system in breast cancer cells, conjugation of MSN-Gd3+ with cysteine is used to enhance cancer cellular uptake of Gd3+. Reactions designed to make different covalent bonds between MSNs and cysteine to investigate impact of cysteine conjugation of MSNs-Gd3+ on uptake of Gd3+ by breast cancer cells. Cysteine amino acids were attached to the surface of MSNs via its three functional groups using three different conjugation methods. Therefore, the external surface of MSNs were first modified by three different linkers to create amine, epoxy, and isocyanate groups on the surface of MSNs, then pores loaded with Gd3+ complexes and reacted with toile, epoxy, and amine groups of cysteine, respectively (nanoprobe A, B and C). The nanoprobes were characterized using different techniques, including (scanning electron microscope) SEM, Brunauer–Emmett–Teller BET, dynamic light scattering (DLS) and Fourier Transform Infrared (FTIR). The intracellular uptake of nanoprobes by human dermal fibroblasts (HDF) and human breast adenocarcinoma cells (MCF-7) was investigated using inductively coupled plasma atomic emission spectrometer (ICP-AES). Results demonstrated that accumulation of Gd3+ in cancer cells is highly related to method of cysteine conjugation. The amount of Gd3+ was taken by cancer cells increased 7 folds, when thiol group of cysteine was responsible to make covalent bond with MSNs, in other words when the zwitterionic form of cysteine was on the surface (nanoprobe B). The average intracellular uptake of Gd3+ by cancer cells was 0.5±0.09 pg/cell. On the other hand, uptake of Gd3+ delivered by nanoprobe B into cancer cells was up to 4.7 times higher than normal cells. No appreciable cytotoxicity was seen using HDF and MCF-7 cell lines. This study provides MRI nanoprobes using suitable conjugation of Gd3+ based MSNs with cysteine for next studies about MR imaging of cancer.

Trastuzumab is a specific monoclonal antibody used for therapeutic of the human epidermal growth factor receptor 2 (HER-2) -positive metastatic breast cancer. But, resistance to trastuzumab is a major obstacle in clinical efficiency.  During the past years, several studies have been done to find the mechanisms contributing to trastuzumab resistance. Previous studies have highlighted that bone morphogenic protein (BMP) signaling can indicate a pathway in cancer for sensitizing cells to chemotherapy. Also, it was suggested that Caveolin-1 is essential for the formation of caveolae and endocytic membrane transport and has a critical role in drug resistance and metastasis in cancer. The purpose of this study was to assess the expression of BMP receptor type1A (BMPR1A) and Caveolin-1 genes in compare with trastuzumab-sensitive and resistance BT-474 cells. Trastuzumab-resistant BT474 cells were established by continuous subjection to trastuzumab for six months. Then, an MTT assay was done for determining the resistance. After that, the Expression of BMPR1A and Caveolin-1levels were assessed through real-time PCR. Caveolin-1 expression levels increased significantly (2.4 fold, p<0.05) whereas BMPR1A levels down-regulated significantly (8.26 fold, p<0.05) in BT474-R compared to the parental cells. Our results proposed that BMPR1A and CAV1 regulation take part in BT-474 trastuzumab resistance breast cancer. Therefore, further experiments are required to confirm the role/s of BMPR1A and CAV1 in trastuzumab resistance breast cancer.