A scanning-fiber-based method developed for imaging bioengineered tissue constructs such as synthetic carotid arteries is reported. Our approach is based on directly embedding one or more hollow-core silica fibers within the tissue scaffold to function as micro-imaging channels (MIC). The imaging process is carried out by translating and rotating an angle-polished fiber micro-mirror within the MIC to scan excitation light across the tissue scaffold. The locally emitted fluorescent signals are captured using an electron multiplying CCD camera and then mapped into fluorophore distributions according to fiber micro-mirror positions. Using an optical phantom composed of fluorescent microspheres, tissue scaffolds, and porcine skin, we demonstrated single-cell-level imaging resolution (20 to 30 μm) at an imaging depth that exceeds the photon transport mean free path by one order of magnitude. This result suggests that the imaging depth is no longer constrained by photon scattering, but rather by the requirement that the fluorophore signal overcomes the background “noise” generated by processes such as scaffold autofluorescence. Finally, we demonstrated the compatibility of our imaging method with tissue engineering by visualizing endothelial cells labeled with green fluorescent protein through a ∼500 μm thick and highly scattering electrospun scaffold.
The degree by which optical properties of tumors are altered following introduction of carbon nanotubes (CNTs) of varying concentration and type is poorly understood, making it difficult to predict the impact of CNT inclusion on the photothermal response to laser therapies. Optical properties were measured of phantoms representative of breast tumor tissue incorporated with multiwalled carbon nanotubes (MWNTs), single-walled carbon nanotubes (SWNTs), and single-walled carbon nanohorns (SWNHs) of varying concentration (0.01-0.1 mg/ml). Tissue phantoms were made from sodium alginate (3 g/ml) incorporated with polystyrene microbeads (3 μm diam and 1 mg/ml) and talc-France powder (40 mg/ml). Absorption (μa) and reduced scattering (μs′) coefficients of phantoms containing CNTs were determined by the inverse adding-doubling algorithm for the wavelength range of 400-1300 nm. Optical properties of phantoms without CNTs were in the range of μa = 1.04-0.06 mm−1 and μs′ = 0.05-0.07 mm−1 at a wavelength of 900 nm, which corresponds with published data for human breast tumor tissue. Incorporating MWNTs, SWNTs, and SWNHs in phantoms with a concentration of 0.1 mg/ml increased (μa) by 20- to 30-fold, 5- to 6-fold, and 9- to 14-fold, respectively, for the wavelength range of 800-1100 nm with minimal change in μs′ (1.2- to 1.3-fold). Introduction of CNTs into tissue phantoms increased absorption, providing a means to enhance photothermal therapy.
Laser therapies can provide a minimally invasive treatment alternative to surgical resection of tumors. However, the
effectiveness of these therapies is limited due to nonspecific heating of target tissue which often leads to healthy tissue
injury and extended treatment durations. These therapies can be further compromised due to heat shock protein (HSP)
induction in tumor regions where non-lethal temperature elevation occurs, thereby imparting enhanced tumor cell
viability and resistance to subsequent chemotherapy and radiation treatments. Introducing multi-walled nanotubes
(MWNT) into target tissue prior to laser irradiation increases heating selectivity permitting more precise thermal energy
delivery to the tumor region and enhances thermal deposition thereby increasing tumor injury and reducing HSP
expression induction. This study investigated the impact of MWNT inclusion in untreated and laser irradiated monolayer
cell culture and cell phantom model. Cell viability remained high for all samples with MWNT inclusion and cells
integrated into alginate phantoms, demonstrating the non-toxic nature of both MWNTs and alginate phantom models.
Following, laser irradiation samples with MWNT inclusion exhibited dramatic temperature elevations and decreased cell
viability compared to samples without MWNT. In the cell monolayer studies, laser irradiation of samples with MWNT
inclusion experienced up-regulated HSP27, 70 and 90 expression as compared to laser only or untreated samples due to
greater temperature increases albeit below the threshold for cell death. Further tuning of laser parameters will permit
effective cell killing and down-regulation of HSP. Due to optimal tuning of laser parameters and inclusion of MWNT in
phantom models, extensive temperature elevations and cell death occurred, demonstrating MWNT-mediated laser
therapy as a viable therapy option when parameters are optimized. In conclusion, MWNT-mediated laser therapies show
great promise for effective tumor destruction, but require determination of appropriate MWNT characteristics and laser
parameters for maximum tumor destruction.
Thermal therapy efficacy can be diminished due to heat shock protein (HSP) induction in regions of a tumor where temperatures are insufficient to coagulate proteins. HSP expression enhances tumor cell viability and imparts resistance to chemotherapy and radiation treatments, which are generally employed in conjunction with hyperthermia. Therefore, an understanding of the thermally induced HSP expression within the targeted tumor must be incorporated into the treatment plan to optimize the thermal dose delivery and permit prediction of the overall tissue response. A treatment planning computational model capable of predicting the temperature, HSP27 and HSP70 expression, and damage fraction distributions associated with laser heating in healthy prostate tissue and tumors is presented. Measured thermally induced HSP27 and HSP70 expression kinetics and injury data for normal and cancerous prostate cells and prostate tumors are employed to create the first HSP expression predictive model and formulate an Arrhenius damage model. The correlation coefficients between measured and model predicted temperature, HSP27, and HSP70 were 0.98, 0.99, and 0.99, respectively, confirming the accuracy of the model. Utilization of the treatment planning model in the design of prostate cancer thermal therapies can enable optimization of the treatment outcome by controlling HSP expression and injury.
Heat shock proteins (HSP) are critical components of a complex defense mechanism essential for preserving cell survival under adverse environmental conditions. It is inevitable that hyperthermia will enhance tumor tissue viability, due to HSP expression in regions where temperatures are insufficient to coagulate proteins, and would likely increase the probability of cancer recurrence. Although hyperthermia therapy is commonly used in conjunction with radiotherapy, chemotherapy, and gene therapy to increase therapeutic effectiveness, the efficacy of these therapies can be substantially hindered due to HSP expression when hyperthermia is applied prior to these procedures. Therefore, in planning hyperthermia protocols, prediction of the HSP response of the tumor must be incorporated into the treatment plan to optimize the thermal dose delivery and permit prediction of overall tissue response. In this paper, we present a highly accurate, adaptive, finite element tumor model capable of predicting the HSP expression distribution and tissue damage region based on measured cellular data when hyperthermia protocols are specified. Cubic spline representations of HSP27 and HSP70, and Arrhenius damage models were integrated into the finite element model to enable prediction of the HSP expression and damage distribution in the tissue following laser heating. Application of the model can enable optimized treatment planning by controlling of the tissue response to therapy based on accurate prediction of the HSP expression and cell damage distribution.
Conference Committee Involvement (10)
Optical Interactions with Tissue and Cells XXXI
1 February 2020 | San Francisco, California, United States
Optical Interactions with Tissue and Cells XXX
2 February 2019 | San Francisco, California, United States
Optical Interactions with Tissue and Cells XXIX
29 January 2018 | San Francisco, California, United States
Optical Interactions with Tissue and Cells XXVIII
30 January 2017 | San Francisco, California, United States
Optical Interactions with Tissue and Cells XXVII
14 February 2016 | San Francisco, California, United States
Optical Interactions with Tissue and Cells XXVI
8 February 2015 | San Francisco, California, United States
Optical Interactions with Tissue and Cells XXV
3 February 2014 | San Francisco, California, United States
Optical Interactions with Tissue and Cells XXIV
5 February 2013 | San Francisco, California, United States
Optical Interactions with Tissue and Cells XXIII
23 January 2012 | San Francisco, California, United States
Optical Interactions with Tissue and Cells XXII
24 January 2011 | San Francisco, California, United States
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