Nonlinear optical response of cancer cells following conventional and nano-technology based treatment strategies: Results of chemo-, thermo- and radiation therapies.

BACKGROUND: Although traditional treatments are able to increase cancer survival rate, undesirable impact on off-target tissues are considered a limitation of these approaches. Nanotechnology-based treatments have been proposed as a possible option to enhance targeting., Further,current methods for evaluating cellular damage, are time consuming, highly dependent on the operator skills, and expensive. The aim of this study was to evaluate the capability of nonlinear optical response of cells to determine cellular damages during conventional and nano-technology based treatments. METHODS: Three different cancer cell lines, CT26, KB, and MCF-7 were used in this study. The alginate hydrogel co-loaded with cisplatin and Au nanoparticle (ACA) nanocomplex and gold-coated iron oxide nanoparticle (Au@IONP) were considered for chemo- and chemo-photothermal therapies, and thermo-radiation therapy, respectively. The sign and value of nonlinear optical absorption coefficient and imaginary part of the third-order nonlinear susceptibility of cells were computed. MTT assay was utilized as a reference method. RESULTS: The value of nonlinear optical indices increased with increasing cellular damage and cell death. The linear regression analysis indicated high correlation between nonlinear optical indices and MTT results, in all treatments. CONCLUSION: The nonlinear optical indices are robust from confounding factors, namely treatment approach (traditional and nano-technology based), treatment modality (chemotherapy, thermotherapy, photothermal therapy, and radiation therapy), and cell types. Nonlinear optical properties of cells can be used as a rapid estimation method for cell damage, at the nanoscale level.

Z-scan method to measure the nonlinear optical behavior of cells for evaluating the cytotoxic effects of chemotherapy and hyperthermia treatments.

The effects of new treatments must be investigated in vitro before using clinically or in vivo. The aim of this study was to introduce the Z-scan technique as a fast, accurate, inexpensive, and safe in vitro method to distinguish the cytotoxic effects of various treatments. C6 and OLN-93 cell lines were prepared and treated with Temozolomide (TMZ), radiofrequency hyperthermia (HT), and chemo-hyperthermia (HT+TMZ). The cytotoxic effects of different treatments on both cell lines were evaluated using colony formation assay and Z-scan method. The results of colony assay showed that the surviving fraction (SF) of C6 cells treated with TMZ, HT, and HT + TMZ were significantly decreased compared to the control group. Whereas, hyperthermia treatment had no significant effect on the SF of OLN-93 cells. The results of Z-scan technique indicated that the control group of C6 cells had the negative nonlinear refractive index (n2). Whereas, the C6 cells treated with HT, TMZ, and HT + TMZ had the positive n2 index. The sign of n2 index in the control and HT groups of OLN-93 cells was positive but treatment of cells with TMZ and HT + TMZ changed the sign of it. Moreover, with increasing the cytotoxic effects of different treatments, the SF value of both cell lines decreased and the magnitude of n2 index increased. The results of Z-scan technique were completely in line with the results of colony assay. Therefore, Z-scan method could distinguish the cytotoxic effects of various treatments by examining the nonlinear optical properties of the samples.

Magneto-plasmonic nanoparticle mediated thermo-radiotherapy significantly affects the nonlinear optical properties of treated cancer cells.

In order to determine the level of cell damage in cancerous cells, current cytogenetic tests have limitations such as time consumption and high cost. The aim of this study was to demonstrate the ability of nonlinear refractive (NLR) index as a predictor of breast cell damage caused by magneto-plasmonic nanoparticle based thermo-radiotherapy treatments. MCF-7 breast cancer cells were subjected individually to the treatment of radiation, radio-frequency (RF) hyperthermia, and radiation + RF hyperthermia. These treatments were repeated in the presence of magneto-plasmonic nanoparticle (Au@IONP). The MTT and nonlinear optical assays were used to evaluate the damage induced by different treatment modalities. The results of MTT were correlated with Z-scan, as the magnitude of nonlinear refraction increased with higher intensity of induced cell damages. In this regard, the lowest cell viability (38 %,) and highest magnitude of NLR index (+28.12) were obtained from combination of radiation (at 4 Gy dose) and hyperthermia treatment in the presence of nanoparticles. The proposed optical index (NLR) indicated high capability and can be used as an auxiliary tool to monitor induced cell damage during different treatment strategies. This technique is fast, noninvasive, does not impose cost, and finally does not waste materials.

The capability of nonlinear optical characteristics as a predictor for cellular uptake of nanoparticles and cell damage.

Current methods for determining the cellular effects of a treatment modality need expensive materials and much time to provide a researcher with results. The aim of this study was to evaluate the potential of nonlinear optical characteristics of cancer cells using Z-scan technique to monitor the level of cellular uptake and cell damage caused by a nanotechnology based treatment modality. Two nanocomplexes were synthesized and characterized. The first one was made of alginate hydrogel co-loaded with cisplatin and gold nanoparticles (AuNPs) named as ACA nanocomplex. The second one, named as AA nanocomplex, was the same as ACA, but without cisplatin and this AA nanocomplex was considered as the control for ACA. Different groups of CT26 mouse colon cancer cell line received various treatments of cisplatin, ACA, and AA nanocomplexes and then the samples were prepared for Z-scan studies. The MTT assay was used to evaluate the cytotoxicity induced by different treatment modalities. Transmission electron microscopy (TEM) and inductively coupled plasma-mass spectrometry (ICP-MS) were used for qualitative and quantitative assessments of the level of AuNPs cellular uptake. The trend of nonlinear optical properties changes for treated cells was in agreement with MTT, TEM and ICP-MS results. Z-scan technique was able to successfully indicate the occurrence of cell damage. It was also capable to determine the intensity of cell damage induced by ACA nanocomplex in comparison to free cisplatin. Furthermore, Z-scan results showed that it was able to discriminate the differences of optical properties of the cells incubated with ACA nanocomplex for various incubation times. Nonlinear optical characteristics of a cell may be considered as a reliable indicator to predict the level of cellular effects induced by a nanotechnology based treatment modality. The protocol suggested in this article does not waste materials, not take much time to provide the results, and it is inexpensive technique.

Evaluation of nonlinear optical behavior of mouse colon cancer cell line CT26 in hyperthermia treatment.

Hyperthermia treatment can induce component changes on cell. This study explored the potential of Z-scan to improve accuracy in the identification of subtle differences in mouse colon cancer cell line CT26 during hyperthermia treatment. Twenty-one samples were subjected individually to treatment of hyperthermia at 41, 43, and 45 °C. Each hyperthermia treatment was done in six different time (15, 30, 45, 60, 75, and 90 min). Two optical setups were used to investigate the linear and nonlinear optical behavior of samples. Prior to the Z-scan technique, all samples were fixed with 1 mL of 5% paraformaldehyde. The linear optical setup indicated that extinction coefficient cannot monitor cell changes at different treatment regimes. But the nonlinear behavior of CT26 in all hyperthermia treatment regimens was different. By increasing the time and/or temperature of hyperthermia treatments, change in the sign of nonlinear refractive index from negative to positive occurred in earlier time intervals. This phenomenon was seen for 41, 43, and 45 °C in 75, 60, and 45 min, respectively. The results showed that the Z-scan technique is a reliable method with the potential to characterize cell changes during hyperthermia treatment regimes. Nonlinear refractive index can be used as a new index for evaluation of cell damage.

Ultrastructural and optical characteristics of cancer cells treated by a nanotechnology based chemo-photothermal therapy method.

The current chemotherapy method demonstrates the need for improvement in terms of efficacy and safety. Given the beneficiary effect of heat in combination with chemotherapy, the purpose of this study is to develop a multifunctional nanoplatform by co-incorporating gold nanoparticles (AuNPs) as photothermal agent and cisplatin as anticancer drug into alginate hydrogel (named as ACA) to enable concurrent thermo-chemotherapy. The in vitro cytotoxicity experiment showed that the as-developed nanocomplex was able to induce greater cytotoxicity in KB human nasopharyngeal cancer cells compared to free cisplatin at the same concentration. Moreover, the interaction of ACA and laser irradiation acted synergistically and resulted in higher cell death rate compared to separate application of photothermal therapy and chemotherapy. The micrograph of KB cells also revealed that ACA was able to selectively accumulate into the mitochondria, so that laser irradiation of KB cells pre-treated with ACA resulted in intensive morphological damages such as plasma membrane disruption, chromatin condensation, autophagic vacuoles formation and organelle degeneration. Moreover, the sign and magnitude of optical nonlinear refractive index measured by Z-scan technique was shown to be significantly altered in cells exposed to ACA with and without laser irradiation. Consequently, the nanocomplex developed herein could be a promising platform to combine photothermal therapy and chemotherapy effectively, thereby achieving synergistic therapeutic outcome.

Evaluation of nonlinear optical differences between breast cancer cell lines SK-BR-3 and MCF-7; an in vitro study.

BACKGROUND: This study aimed to explore the potential of the Z-scan technique to improve accuracy in identifying SK-BR-3 and MCF-7 breast cancer cell lines. METHODS: Three in vitro samples were prepared for each breast cancer cell line. A closed-aperture Z-scan technique was used to measure the sign and magnitude of the nonlinear refractive index of each sample. Prior to the Z-scan, all samples were fixed with 1 mL of 5% paraformaldehyde. RESULTS: The sign of the nonlinear refractive indices of MCF-7 and SK-BR-3 breast cancer cell lines were negative and positive, respectively. The repeated Z-scan measurements for all samples of each cell line were similar. CONCLUSION: The results indicated that the proposed bio-optical method is a reliable method for characterizing differences in various breast cancer cell types. It is suggested that the nonlinear refractive index of cells be considered as an indicator for differentiating various breast cell lines from each other.