Assessing fluorescence detection and effective photothermal therapy of near-infrared polymer nanoparticles using alginate tissue phantoms.

OBJECTIVE: Photothermal therapy (PTT) uses light absorbing materials to generate heat for treatment of diseases, like cancer. The advantages of using PTT components that absorb in the near-infrared (NIR) include reduced tissue auto-fluorescence and higher penetration depths. However, NIR laser light can still be scattered and absorbed by biological tissues, thus decreasing the amount of the energy reaching the PTT agents. We have developed two distinct formulations of NIR-absorbing nanoparticles, one which can be utilized for PTT only, and another for both PTT and fluorescence imaging of colorectal cancer. In this work, the fluorescence detection limit and the PTT heating potential of the two nanoparticle types were determined using alginate tissue phantoms. The objective of this study was to determine the PTT efficiency and theranostic potential of the nanoparticles by irradiating 3D collagen tumor spheroids, containing nanoparticles and CT26 mouse colorectal cancer cells, through increasing tissue phantom thicknesses and then quantifying cell death. Materials and Methods Our lab has previously developed nanoparticles based on the semiconducting, conjugated polymer poly[4,4-bis(2-ethylhexyl)-cyclopenta[2,1-b;3,4-b']dithiophene-2,6-diyl-alt-2,1,3-benzoselenadiazole-4,7-diyl] (PCPDTBSe). We have also made a hybrid nanoparticle that heats and fluoresces by combining PCPDTBSe polymer with the fluorescent poly[(9,9-dihexylfluorene)-co-2,1,3-benzothiadiazole-co-4,7-di(thiophen-2-yl)-2,1,3-benzothiadiazole] (PFBTDBT10) polymer to yield nanoparticles termed Hybrid Donor-Acceptor Polymer Particles (H-DAPPs). H-DAPPs and PCPDTBSe nanoparticles were added to three-dimensional collagen gel tumor spheroids in order to represent nanoparticles in a tumor. Alginate tissue phantoms, comprised of an optical scattering agent (Intralipid) and an optical absorbing material (hemoglobin) in order to mirror biological tissue scattering effects, were used to simulate increasing tissue thickness between the nanoparticles and the PTT energy source. RESULTS: Fluorescence from the H-DAPPs was detectable through 6 mm of tissue phantoms. It was found that less than 10% of the laser energy could penetrate through 9 mm of tissue phantoms and only 60% of the laser energy passed through the 1.5 mm phantoms, regardless of laser power. PTT experiments, using 800 nm light at 2.2 W/cm2 for 60 s through tissue phantoms to stimulate nanoparticle-doped tumor spheroids, showed 55% cell death through 3 mm of tissue phantoms using H-DAPPs. Results from using the PCPDTBSe nanoparticles showed 72% cell death through 3 mm and over 50% cell death through 6 mm of tissue phantoms. CONCLUSION: The results of this work validated the heating potential and fluorescence detection limitations of two theranostic polymer nanoparticles by utilizing alginate tissue phantoms and 3D tumor spheroids. H-DAPPs and PCPDTBSe polymer nanoparticles can be utilized as effective PTT agents by exploiting their absorption of NIR light and H-DAPPs have advantageous fluorescence for imaging colorectal cancer. The data generated from this study design can allow for other NIR absorbing and fluorescing nanoparticle formulations to be evaluated prior to in vivo experimentation. Lasers Surg. Med. 50:1040-1049, 2018. © 2018 Wiley Periodicals, Inc.

Dual wavelength stimulation of polymeric nanoparticles for photothermal therapy.

BACKGROUND AND OBJECTIVE: Photothermal therapy (PTT) has several applications in the areas of wound healing, pain management, bacterial infection control, and cancer treatment dependent on the temperature that is generated. PTT is often used exclusively with near infrared (NIR) light and most nanoparticles (NP) used for PTT are designed to absorb within one narrow range of wavelengths. We have developed a dual-wavelength photothermal therapy by capitalizing on the dual absorption of nanoparticles in the blue and NIR range. MATERIALS AND METHODS: Our lab has previously developed NP based on the semiconducting, conjugated polymer poly[4,4-bis(2-ethylhexyl)-cyclopenta[2,1-b;3,4-b']dithiophene-2,6-diyl-alt-2,1,3-benzoselenadiazole-4,7-diyl] (PCPDTBSe). The NP have strong absorption in the blue and NIR regions. In this report, we have explored the heat generated by PCPDTBSe NP using simultaneous delivery of 450 and 800 nm light, either independently or together for photothermal ablation of mouse colorectal cancer cells. RESULTS: The heat generation studies indicated that the use of either 450 or 800 nm wavelengths at the same fluences produced approximately the same temperature change of deionized water. Fluences of 114.6 and 229.2 J/cm2 , utilizing 450 or 800 nm light applied individually resulted in temperatures of 8-47°C above ambient temperature, leading to a 90% reduction in cell viability. Simultaneous stimulation of the PCPDTBSe NP with 450 and 800 nm light effectively doubles the effective power delivered, resulting in temperatures 18-63°C above ambient and 100% photothermal ablation of the colorectal cancer cells. CONCLUSION: The results of this study demonstrate that PCPDTBSe polymer NP can be utilized as effective PTT agents by capitalizing on their dual absorption of both blue and NIR light. Lasers Surg. Med. 48:893-902, 2016. © 2016 Wiley Periodicals, Inc.

Multi-Walled Carbon Nanotubes Inhibit Breast Cancer Cell Migration.

According to the American Cancer Society, breast cancer is the second leading cause of cancer death in the US. Cancerous cells may have inadequate adhesions to the extracellular matrix and adjacent cells. Previous work has suggested that restoring these contacts may negate the cancer phenotype. This work aims to restore those contacts using multi-walled carbon nanotubes (MWNTs). Varying concentrations of carboxylated MWNTs in water, with or without type I collagen, were dried to create a thin film upon which one of three breast cell lines were seeded: cancerous and metastatic MDA- MB-231 cells, cancerous but non-metastatic MCF7 cells, or non-cancerous MCF10A cells. Proliferation, adhesion, scratch and autophagy assays, western blots, and immunochemical staining were used to assess adhesion and E-cadherin expression. Breast cancer cells grown on a MWNT-collagen coated surface displayed increased adhesion and decreased migration which correlated with an increase in E-cadherin. This work suggests an alternative approach to cancer treatment by physically mediating the cells' microenvironment.

Multi-walled nanotubes for cellular reprogramming of cancer.

Triple negative breast cancer is exceptionally difficult to treat due to the lack of distinguishing biomarkers for drug targeting. An alternative approach based on recent data indicates that these cells may be more susceptible to mechanical influences, such as alterations in the tumor stroma. Three dimensional collagen gels containing co-cultures of mesenchymal cells and MDA-MB-231 cancer cells were utilized to explore the effects of multi-walled nanotubes (MWNT) on cell contraction, invasion, viability, MMP-9 expression, and migration of breast cancer cells. MWNT were able to restrict each of these features for the cancer cells without impeding the associated mesenchymal cells. MWNT-collagen gels are useful tools for cellular reprogramming of cancer cells and should be considered in greater detail as a potential agent for therapeutic treatment of triple-negative breast cancer. FROM THE CLINICAL EDITOR: Breast cancer is still a leading cause of death for women worldwide. One subtype of this cancer which is very aggressive is the triple negative breast cancer. The behavior of tumors may be affected by the tumor stromal environment. In this study, the authors investigated the effects of multi-walled nanotubes (MWNT) on tumor cell biology. The positive findings may point a new way in using this modality for treatment of triple-negative breast cancer in the future.

Differential response of MCF7, MDA-MB-231, and MCF 10A cells to hyperthermia, silver nanoparticles and silver nanoparticle-induced photothermal therapy.

PURPOSE: Silver nanoparticles (Ag NP) can generate heat upon exposure to infrared light. The in vitro response of breast cell lines to Ag NP, both with and without nanoparticle-induced heating was evaluated. MATERIALS AND METHODS: Ag NP heat generation, intracellular silver concentration, and cell viability of MDA-MB-231, MCF7, and MCF 10A breast cells with Ag NP alone, or after exposure to 0.79 or 2.94 W/cm2 of 800 nm light were evaluated. RESULTS: The concentration of Ag NP to induce sufficient heat for cell death, upon exposure to 800 nm light, was 5-250 µg/mL. Clonogenics assay indicates a cytotoxic response of MCF7 (45% decrease) and MDA-MB-231 (80% decrease) cells to 10 µg/mL, whereas MCF 10A had a 25% increase. Without Ag NP, MDA-MB-231 cells were more susceptible to hyperthermia, compared to MCF7 and MCF 10A cells. Clonogenics assay of Ag NP-induced photothermal ablation demonstrated that MCF 10A cells have the highest survival fraction. MCF7 cells had more silver in the cytoplasm, MDA-MB-231 cells had more in the nuclei, and MCF 10A cells had equivalent concentrations in the cytoplasm and nuclei. CONCLUSIONS: Ag NP are effective photothermal agents. A secondary benefit is the differential response of breast cancer cells to Ag NP-induced hyperthermia, due to increased intracellular silver content, compared to non-tumorigenic breast epithelial cells.

A comparative study of the photothermal efficiency of electrically conducting poly(3,4-ethylenedioxythiophene)-based nanomaterials with cancer cells.

The photothermal efficiency of two similar organic nanomaterials, poly(3,4-ethylenedioxythiophene):poly(4-styrene-sulfonate) (PEDOT:PSS) nanoparticles and poly(3,4-ethylenedioxythiophene) (PEDOT) nanotubes, are compared. The PEDOT:PSS nanoparticles ranged from 100-200 nm in diameter, while the PEDOT nanotubes ranged from 200-400 nm in diameter and 4-10 microm in length. By changing the aspect ratio of the PEDOT nanomaterials from a spherical to a tubular shape, interesting differences in the optical and electronic properties of the materials were realized. Because of this, the PEDOT nanotubes were shown to generate on average approximately to 10 degrees C better internal heating for similar concentrations compared to the PEDOT:PSS nanoparticles. Cytotoxicity studies of both nanomaterials showed no significant toxicity towards RKO or HCT116 colorectal cancer cells in the absence of NIR light. The NIR-mediated photothermal efficiency of the PEDOT:PSS nanoparticles and the PEDOT nanotubes were compared in-vitro. A cell viability assay was performed and at the highest concentration (0.1 mg/mL) of nanomaterial, cell survival was close to 20% for the PEDOT:PSS nanoparticles with both RKO and HCT116 cells. Consequently, cell survival for the PEDOT nanotubes was less than 5% for both RKO and HCT116 cells. An in-vitro three dimensional tumor model was assembled using collagen gel tissue phantoms. The depth of heat penetration from the PEDOT nanotubes into the tissue phantoms, along with cell viability of RKO and HCT116 cells was determined and quantified.

Low band gap donor-acceptor conjugated polymer nanoparticles and their NIR-mediated thermal ablation of cancer cells.

Low band gap D-A conjugated PNs consisting of 2-ethylhexyl cyclopentadithiophene co-polymerized with 2,1,3-benzothiadiazole (for nano-PCPDTBT) or 2,1,3-benzoselenadiazole (for nano-PCPDTBSe) have been developed. The PNs are stable in aqueous media and showed no significant toxicity up to 1 mg · mL(-1) . Upon exposure to 808 nm light, the PNs generated temperatures above 50 °C. Photothermal ablation studies of the PNs with RKO and HCT116 colorectal cancer cells were performed. At concentrations above 100 µg · mL(-1) for nano-PCPDTBSe, cell viability was less than 20%, while at concentrations above 62 µg · mL(-1) for nano-PCPDTBT, cell viability was less than 10%. The results of this work demonstrate that low band gap D-A conjugated polymers 1) can be formed into nanoparticles that are stable in aqueous media; 2) are non-toxic until stimulated by IR light and 3) have a high photothermal efficiency.

Rapid photothermal intracellular drug delivery using multiwalled carbon nanotubes.

Carbon nanotubes are unique materials that absorb infrared (IR) radiation, especially between 700 and 1100 nm, where body tissues are most transparent. Absorbed IR promotes molecular oscillation leading to efficient heating of the surrounding environment. A method to enhance drug localization for peritoneal malignancies is perfusion of warm (40-42 degrees C) chemotherapeutic agents in the abdomen. However, all tissues in the peritoneal cavity are subjected to enhanced drug delivery due to increased cell membrane permeability at hyperthermic temperatures. Here we show that rapid heating (within ten seconds) of colorectal cancer cells to 42 degrees C, using infrared stimulation of nanotubes as a heat source, in the presence of the drugs oxaliplatin or mitomycin C, is as effective as two hours of radiative heating at 42 degrees C for the treatment of peritoneal dissemination of colorectal cancer. We demonstrate increased cell membrane permeability due to hyperthermia from multiwalled carbon nanotubes in close proximity to cell membranes and that the amount of drug internalized by colorectal cancer cells heated quickly using carbon nanotubes equals levels achieved during routine application of hyperthermia at 42 degrees C. This approach has the potential to be used as a rapid bench to bedside clinical therapeutic agent with significant impact for localizing chemotherapy agents during the surgical management of peritoneal dissemination of colorectal cancer.

Encapsulated Staphylococcus aureus strains vary in adhesiveness assessed by atomic force microscopy.

Staphylococcus aureus capsular polysaccharides are believed to play a role in adhesion to surfaces and may contribute to their antimicrobial resistance, thereby increasing the rates and severity of associated infections. The purpose of this study was to compare the adhesiveness of distinct S. aureus capsular polysaccharides to determine whether adhesiveness was a general or specific feature across different S. aureus strains. Atomic force microscopy was used to confirm the presence or absence of capsular polysaccharides and to measure adhesive forces on a noncapsulated, serotype 8, and serotype 2 strain of S. aureus. Serotype 8 displayed a larger range of adhesive forces (1-19 nN) than the noncapsulated (0-4 nN) and serotype 2 (0-4 nN) strain. The majority of adhesive forces for serotype 8 were in the 10-15 nN range. Removal of capsular polysaccharides gave a marked decrease in adhesive forces measured for serotype 8 and, to a lesser extent, a decrease for serotype 2. Noncapsulated, serotype 8, and serotype 2 S. aureus had water contact angles of 23.8 (+/-8.9), 34.4 (+/-2.5), and 56.7 (+/-11.2) degrees (mean +/- standard deviation), respectively. For the first time, capsular polysaccharides from serotype 8 (clinically common) and serotype 2 (clinically rare) were demonstrated to have different physical properties, which may account for variations in studies in which clinical isolates are utilized, and the conflict in proposed roles for capsular polysaccharides on S. aureus is explained.