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Method Article

Preparation and Photoacoustic Analysis of Cellular Vehicles Containing Gold Nanorods

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DOI:

10.3791/53328

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May 2nd, 2016

 ,  ,  ,  ,  ,  ,  ,  , 
1Institute of Applied Physics, Italian National Research Council, 2Department of Experimental and Clinical Biomedical Sciences, University of Florence, Firenze, 3Department of Physics and Astronomy, University of Florence, Sesto Fiorentino, 4Department of Pharmacy and Biotechnology, University of Bologna

In This Article

Summary

We show the preparation and address the feasibility of cellular vehicles containing gold nanorods for the photoacoustic imaging of cancer.

Abstract

Gold nanorods are attractive for a range of biomedical applications, such as the photothermal ablation and the photoacoustic imaging of cancer, thanks to their intense optical absorbance in the near-infrared window, low cytotoxicity and potential to home into tumors. However, their delivery to tumors still remains an issue. An innovative approach consists of the exploitation of the tropism of tumor-associated macrophages that may be loaded with gold nanorods in vitro. Here, we describe the preparation and the photoacoustic inspection of cellular vehicles containing gold nanorods. PEGylated gold nanorods are modified with quaternary ammonium compounds, in order to achieve a cationic profile. On contact with murine macrophages in ordinary Petri dishes, these particles are found to undergo massive uptake into endocytic vesicles. Then these cells are embedded in biopolymeric hydrogels, which are used to verify that the stability of photoacoustic conversion of the particles is retained in their inclusion into cellular vehicles. We are confident that these results may provide new inspiration for the development of novel strategies to deliver plasmonic particles to tumors.

Introduction

Over the past decade, various plasmonic particles such as gold nanorods, nanoshells and nanocages, have received considerable attention for applications in biomedical optics1,2,3,4. At variance with standard gold nanospheres, these newer particles resonate in the near infrared (NIR) window that provides for deepest optical penetration through the body and highest optical contrast over endogenous components1. This feature has aroused interest for innovative applications, such as the photoacoustic (PA) imaging and the photothermal ablation of cancer. However, several issues restrain the clinical penetration of these particles. For instance, their optical activation tends to induce their overheating and to modify their functional shapes towards more spherical profiles, which drives a photoinstability5,6,7,8,9. Another issue that dominates the scientific debate is their systemic delivery into tumors. In particular, gold nanorods combine sizes that are ideal to pervade tumors that display enhanced permeability and retention and ease of conjugation with specific probes of malignant markers. Therefore, their preparation for a direct injection into the bloodstream is perceived as a feasible scheme10,11,12,13. However, this route remains problematic, with most of the particles becoming captured by the mononuclear phagocyte system10,11,12. In addition, another concern is the optical and biochemical stability of the particles after circulation through the body14. When particles lose their colloidal stability and aggregate, their plasmonic features and heat transfer dynamics may suffer from plasmonic coupling15,16,17 and cross-overheating18.

More recently, the notion to exploit the tropism of tumor-associated macrophages has emerged as a smart alternative19,20,21. These cells hold an innate ability to detect and pervade tumors with high specificity. Therefore, one perspective may be to isolate these cells from a patient, load them with gold nanorods in vitro and then inject them back into the patient, with the intent to use them as cellular vehicles in charge of the delivery. Another advantage would be to gain more control over the optical and biochemical stability of the particles, because their biological interface would be constructed in vitro. Still, the performances of these cellular vehicles as optical contrast agents need a critical analysis.

In this work, we describe the preparation and critical issues of cellular vehicles containing gold nanorods for the PA imaging of cancer. PEGylated gold nanorods are modified with quaternary ammonium compounds22, in order to achieve a cationic profile that is expected to promote their interactions with plasmatic membranes23,24. These particles undergo efficient and unspecific uptake from most cellular kinds, hopefully without interfering much with their biological functions. Murine macrophages are loaded with up to as many as 200̇,000 cationic gold nanorods per cell, which become confined within tight endocytic vesicles. This configuration should arise concern, because of the threat of plasmonic coupling and cross-overheating inside these vesicles. Therefore, the macrophages are embedded in biopolymeric hydrogels that mimic biological tissues, in order to verify that most of the stability of PA conversion of the particles is retained in the transfer from the growth medium to the endocytic vesicles. Effective measurement criteria are worked out in order to measure the stability of PA conversion under conditions of immediate interest for PA imaging. A reshaping threshold is set at the very onset of optical instability after a train of 50 laser pulses with the typical repetition rate of 10 Hz.

We are confident that these results may provide momentum for the development of novel strategies to deliver plasmonic particles to tumors.

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Protocol

Note: All concentrations of gold nanorods are expressed in terms of nominal Au molarities. For comparison with other works, note that 1 M Au roughly corresponds to 20 µM gold nanorods, in our case.

1. Preparation of Cationic Gold Nanorods

Note: The method begins with the synthesis of cetrimonium bromide (CTAB)-capped gold nanorods by the autocatalytic reduction of HAuCl4 with ascorbic acid, according to the protocol introduced by Nikoobakht et al.25 and adapted according to Ratto et al.26. Then these gold nanorods are modified in order to gain more biocompatibility and affinity for plasmatic membranes, by the combination of polyethylene glycol strands10,11,27,28 and quaternary ammonium compounds22.

  1. Purify 24 ml CTAB-capped gold nanorods at a concentration of 450 µM Au by two cycles of centrifugation (12,000 x g, 30 min) and decantation. Make sure that the ratio of dead volume to initial volume is around 1/200 or lower for all centrifugation steps in this protocol. Use 500 µM aqueous CTAB as a washing solution and finally transfer the particles into 6 ml 100 mM acetate buffer at pH 5 containing 500 µM CTAB and 0.005% (v/v) polysorbate 20.
  2. Add 30 µl 10 mM aqueous alpha-methoxy-omega-mercapto-poly(ethylene glycol) (MW ~ 5,000) and leave to react for 30 min at 37 °C.
  3. Add 30 µl 100 mM (11-Mercaptoundecyl)-N,N,N-trimethylammonium bromide in dimethyl sulfoxide and leave at rest for 24 hr at 37 °C.
  4. Next, add 18 ml 0.005% (v/v) polysorbate 20 in water and purify these particles by four cycles of centrifugation (12,000 x g, 30 min) and decantation. Use 0.005% (v/v) polysorbate 20 in water as washing solution and finally transfer the particles into 2.4 ml sterile PBS at pH 7.4. The final nominal concentration of gold is 4.5 mM.

2. Loading of Murine Macrophages with Gold Nanorods

  1. Use the monocyte/macrophagic cell line J774a.1 and DMEM supplemented with 10% fetal bovine serum, 1 mM glutamine, 100 units/ml penicillin and 100 µg/ml streptomycin as culture medium. Plate 5 x 105 cells in four Petri dishes of 60 mm diameter and allow them to grow for 24 hr, so as to be subconfluent at the time of detachment (see step 2.2).
    1. Throughout the protocol, maintain the cells under standard culture conditions (37 °C, 5% CO2, 95% air and 100% relative humidity). Use a laminar flow cabinet and appropriate personal protective equipment to manipulate the cells.
  2. After 24 hr, load the cells with cationic gold nanorods and prepare them to be embedded into chitosan films:
    1. In order to allow the particles to be taken up by the cells, add an aliquot of 4.5 mM Au cationic gold nanorods in PBS into each Petri dish, so as to achieve a final concentration of 100 µM Au. Leave the Petri dishes in incubation for 24 hr.
    2. Next, observe the cells under an optical microscope to confirm their good conditions and the upload. Cells should exhibit their normal morphology and a number of dark intracellular vesicles. Detach the cells by a scraper, merge those from two Petri dishes, in order to achieve a suitable amount of cells for the following steps (at least 2 x 106 cells), and centrifuge them (120 x g, 6 min) to eliminate any excess of cationic gold nanorods. The cellular pellet should look almost black.
    3. Suspend the pellet in 2 ml PBS and count the cells by the use of a Bürker chamber. Centrifuge a suspension containing 2 x 106 cells (120 x g, 6 min) and fix their pellet in 2 ml 3.6% (w/v) formaldehyde in PBS for ten minutes at room temperature. Finally, wash this pellet three times by centrifugation (120 x g, 6 min) in order to remove the fixative. Use PBS as washing solution.

3. Embedment of Macrophages into Chitosan Films

Note: The peculiar properties of chitosan26,27,28,29 are exploited to produce biomimetic phantoms containing macrophages stained with cationic gold nanorods. With respect to other hydrogels such as agarose, chitosan enables films that are much stronger and thinner, which is critical for PA microscopy6. The fabrication of these phantoms is carried out according to previous protocols29,30,31 with some modifications as prescribed in the followings30.

  1. Prepare an acidified (pH 4.5, obtained by the addition of acetic acid) and viscous 3% (w/v) low molecular weight chitosan (average MW 120 kDa) solution, thoroughly mix it and let it homogenize for 24 hr at 40 °C.
  2. Next, mix murine macrophages containing cationic gold nanorods (2 x 106 cells) with 500 µl of chitosan solution.
  3. In order to obtain ~50 µm thick phantoms, pour 250 mg of the mixture into 1.91 cm2 polystyrene molds and leave them under a nitrogen stream for 24 hr. Thereafter, treat these samples with 500 µl 1 M NaOH, in order to induce cross-linking, and rinse them with 10 ml of ultrapure water.

4. Test of the Stability of Photoacoustic Conversion

Note: The stability of PA conversion is investigated by means of PA experiments with the home-made setup that is described in ref 6.

  1. Suspend a chitosan film containing the macrophages in DI water, for instance by the use of a plastic holder immersed in a Petri dish, so as to keep a distance of ~5 mm from the bottom of the plate. Put this plate onto a micrometric XY stage in order to control the sample position.
  2. Focus a laser beam with ~5 nsec pulse duration in resonance with the longitudinal plasmonic band of the gold nanorods (e.g., from an optical parametric oscillator pumped by the third harmonic of a Q-switched Nd:YAG laser with wavelength range of 400 - 2,500 nm and pulse duration of 5 nsec) perpendicular to the film surface with a ~300 µm spot diameter.
    1. Place an attenuator in front of the laser exit to tune the laser fluence and use a beam splitter to focus part of the laser beam to an energy meter (e.g., a pyroelectric detector) and monitor fluence fluctuations. Maintain the optical fluence below ~1 mJ/cm2 per pulse during the alignment. Use appropriate laser safety eyewear whenever the laser is on.
  3. Dip an ultrasound transducer (frequency range of 1 - 20 MHz) into the Petri dish ~2 mm off of the film surface and adjust its position by using micrometric translations and rotational stages to maximize the PA signal emitted from the film.
  4. Determine a probe fluence FLO that does not damage the sample6:
    1. Irradiate a random point of the sample at a fluence around 1 mJ/cm2 per pulse for at least 500 pulses. For each pulse, acquire the corresponding PA signal from the ultrasound transducer and laser fluence from the energy meter with an oscilloscope. Name the average fluence as FLOtrial.
    2. Calculate the intensity of the PA signal as its peak-to-peak amplitude as a function of pulse number. In order to counterweight the laser intensity fluctuations, normalize the amplitude of each PA signal to the ratio of its own fluence to FLOtrial. Analyze the trend of the normalized PA intensity as a function of pulse number and verify its stability over time.
    3. In the case of instability, repeat steps 4.4.1 to 4.4.3 with a lower value of FLOtrial. In the case of stability, repeat them with a value of FLOtrial higher by ~10%, until a loss of stability arises. Set the probe fluence FLO as the second highest value of FLOtrial that ensures stability.
  5. Measure a reshaping threshold fluence:
    1. Choose another random point of the sample and probe an average PA intensity (ILOa) over 500 pulses at FLO.
    2. Set a nominal fluence greater than FLO and deliver 50 pulses. Name their average fluence as Fexc.
    3. Probe an average PA intensity (ILOb) over 500 pulses at FLO once again. Calculate the ratio R = ILOb / ILOa. A value of R below unity gives evidence of an irreversible change of the optical properties of the sample.
    4. Use the micrometric XY stage to move the film and change the point of the sample at random. Repeat steps 4.5.1 to 4.5.4 with different values of Fexc, so as to take a few values of R below, around and above unity. 15 points are reasonable.
    5. Plot R as a function of Fexc and identify the reshaping threshold fluence Fth as that value when R begins to differ from one beyond statistical uncertainty.6

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Results

Here, the feasibility of cellular vehicles containing gold nanorods for the PA imaging of cancer is shown together with typical outcomes of the protocol.

The TEM images in Figure 1 show the usual appearance of the particles after step 1 and their cellular vehicles after step 2. The preparation of the particles and of the cells for TEM imaging is described elsewhere17. Cationic gold nanorods undergo a ...

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Discussion

The notion to target tumor-associated macrophages is emerging as a powerful concept to combat cancer34,35,36. Here, instead of their destruction, these cells are recruited as cellular vehicles to bring gold nanorods into a tumor, by the exploitation of their tropism. This perspective requires a thoughtful design of the particles, their integration into the cells and their characterization. We have found that the photostability of murine macrophages loaded with cation...

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Disclosures

The authors declare that they have no competing financial interests.

Acknowledgements

This work was partially supported by Regione Toscana and European Community within the frame of the ERANET+ Projects LUS BUBBLE and BI-TRE.

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Materials

List of materials used in this article
NameCompanyCatalog NumberComments
Hexadecyltrimethylammonium bromideSigma-AldrichH6269To synthesize gold nanorods
Gold(III) chloride trihydrateSigma-Aldrich520918To synthesize gold nanorods
Silver nitrateSigma-AldrichS6506To synthesize gold nanorods
L-ascorbic acidSigma-AldrichA5960To synthesize gold nanorods
Sodium borohydrideSigma-AldrichTo synthesize gold nanoseeds
MeO-PEG-SHIris BiotechPEG1171To PEGylate gold nanorods. Molecular weight about 5,000 Da.
Acetic acidSigma-Aldrich320099To PEGylate gold nanorods and solubilize chitosan
Sodium acetateSigma-AldrichS8750To PEGylate gold nanorods
(11-Mercaptoundecyl)-N,N,N-trimethylammonium bromideSigma-Aldrich733305To modify gold nanorods with quaternary ammonium compounds
Dimethyl sulfoxideSigma-Aldrich276855To solubilize (11-mercaptoundecyl)-N,N,N-trimethylammonium bromide
Polysorbate 20Sigma-AldrichP2287To centrifuge PEGylated gold nanorods
PBSLonzaBE17-516FTo suspend gold nanorods before incubation with cells and to treat pellets of cells
J774a.1ATCCTIB-67Monocyte/macrophage murine cell line
DMEMLonzaBE12-707FCell culture medium
FBSLonzaDE14-801FTo be added to cell culture medium
L-glutamineLonzaBE17-605ETo be added to cell culture medium
Penicillin/streptomycinLonzaDE17-602ETo be added to cell culture medium
Petri dishNEST705001Cell culture dish
Cell scraperEuroCloneES7018To detach cells
FormaldehydeFluka47630To fix cells
Chitosan, low molecular weightSigma-Aldrich44886975-85% deacetylated. Molecular weight about 120,000 Da.
Sodium hydroxydeSigma-Aldrich306576To insolubilize chitosan and generate the hydrogel
Polystyrene cell culture platesNEST702011Used as molds to fabricate chitosan hydrogels
Optical parametric oscillator pumped by the third harmonic of a Q-switched Nd:YAG laserContinuum, Santa Clara, USASurelite OPO plusSource of optical excitation for photoacoustic tests
Pyroelectric detector Gentec, Quebec, CanadaQE8SPTo monitor optical fluence for photoacoustic tests
Pre amplified needle hydrophonePrecision Acoustic, Dorset, UKModel with 1 mm sensor diameter and 1-20 MHz frequency rangeTo measure photoacoustic signals

References

  1. Ratto, F., Matteini, P., Centi, S., Rossi, F., Pini, R. Gold nanorods as new nanochromophores for photothermal therapies. J. Biophotonics. (1-2), 4-41 (2011).
  2. Dreaden, E. C., Alkilany, A. M., Huang, X., Murphy, C. J., El-Sayed, M. A. The golden age: gold nanoparticles for biomedicine. Chem. Soc. Rev. 41, 2740-2779 (2012).
  3. Hahn, M. A., Singh, A. K., Sharma, P., Brown, S. C., Moudgil, B. M. Nanoparticles as Contrast Agents for in-Vivo Bioimaging: Current Status and Future Perspectives. Anal. Bioanal. Chem. 399 (1), 3-27 (2011).
  4. Dreaden, E. C., Austin, L. A., Mackey, M. A., El-Sayed, M. A. Size matters: gold nanoparticles in targeted cancer drug delivery. Ther. Deliv. 3 (4), 457-478 (2012).
  5. Manohar, S., Ungureanu, C., Van Leeuwen, T. G. Gold nanorods as molecular contrast agents in photoacoustic imaging: The promises and the caveats. Contrast Media Mol. Imaging. 6 (5), 389-400 (2011).
  6. Cavigli, L., et al. Size Affects the Stability of the Photoacoustic Conversion of Gold Nanorods. J. Phys. Chem. C. 118 (29), 16140-16146 (2014).
  7. Chen, L. -C., et al. Enhanced photoacoustic stability of gold nanorods by silica matrix confinement. J. Biomed. Opt. 15 (1), 016010(2010).
  8. Ratto, F., et al. CW laser-induced photothermal conversion and shape transformation of gold nanodogbones in hydrated chitosan films. J. Nanopart. Res. 13, 4337-4348 (2011).
  9. Mercatelli, R., et al. Quantitative readout of optically encoded gold nanorods using an ordinary dark-field microscope. Nanoscale. 5 (20), 9645-9650 (2013).
  10. Von Maltzahn, G., et al. Computationally guided photothermal tumor therapy using long-circulating gold nanorod antennas. Cancer Res. 69 (9), 3892-3900 (2009).
  11. Jokerst, J. V., Cole, A. J., Van De Sompel, D., Gambhir, S. S. Gold nanorods for ovarian cancer detection with photoacoustic imaging and resection guidance via Raman imaging in living mice. ACS Nano. 6 (11), 10366-10377 (2012).
  12. Huang, X., et al. A reexamination of active and passive tumor targeting by using rod-shaped gold nanocrystals and covalently conjugated peptide ligands. ACS Nano. 4 (10), 5887-5896 (2010).
  13. Alkilany, A. M., Thompson, L. B., Boulos, S. P., Sisco, P. N., Murphy, C. J. Gold nanorods: Their potential for photothermal therapeutics and drug delivery, tempered by the complexity of their biological interactions. Adv. Drug Deliv. Rev. 64, 190-199 (2012).
  14. Centi, S., et al. In vitro assessment of antibody-conjugated gold nanorods for systemic injections. J. Nanobiotechnology. 12, 55(2014).
  15. Jain, P. K., Eustis, S., El-Sayed, M. A. Plasmon coupling in nanorod assemblies: Optical absorption, discrete dipole approximation simulation, and exciton-coupling model. J. Phys. Chem. B. 110 (37), 18243-18253 (2006).
  16. Funston, A. M., Novo, C., Davis, T. J., Mulvaney, P. Plasmon coupling of gold nanorods at short distances and in different geometries. Nano Lett. 9 (4), 1651-1658 (2009).
  17. Mazzoni, M., Ratto, F., Fortunato, C., Centi, S., Tatini, F., Pini, R. Partial Decoupling in Aggregates of Silanized Gold Nanorods. J. Phys. Chem. C. 118 (34), 20018-20025 (2014).
  18. Lapotko, D. O., Lukianova, E., Oraevsky, A. A. Selective laser nano-thermolysis of human leukemia cells with microbubbles generated around clusters of gold nanoparticles. Lasers Surg. Med. 38 (6), 631-642 (2006).
  19. Choi, M. R., et al. A cellular trojan horse for delivery of therapeutic nanoparticles into tumors. Nano Letters. 7 (12), 3759-3765 (2007).
  20. Dreaden, E. C., Mwakwari, S. C., La Austin,, Kieffer, M. J., Oyelere, A. K., El-Sayed, M. A. Small molecule-gold nanorod conjugates selectively target and induce macrophage cytotoxicity towards breast cancer cells. Small. 8 (18), 2819-2822 (2012).
  21. Yang, T. D., et al. Real-time phase-contrast imaging of photothermal treatment of head and neck squamous cell carcinoma: an in vitro study of macrophages as a vector for the delivery of gold nanoshells. J. Biomed. Opt. 17 (12), 128003(2012).
  22. Vigderman, L., Manna, P., Zubarev, E. R. Quantitative Replacement of Cetyl Trimethylammonium Bromide by Cationic Thiol Ligands on the Surface of Gold Nanorods and Their Extremely Large Uptake by Cancer Cells. Angew. Chem. Int. Ed. (English). 51 (3), 636-641 (2012).
  23. Richard, J. P., et al. Cell-penetrating peptides: A reevaluation of the mechanism of cellular uptake. J. Biol. Chem. 278 (1), 585-590 (2003).
  24. Delehanty, J. B., Boeneman, K., Bradburne, C. E., Robertson, K., Bongard, J. E., Medintz, I. L. Peptides for specific intracellular delivery and targeting of nanoparticles: implications for developing nanoparticle-mediated drug delivery. Ther. Deliv. 1, 411-433 (2010).
  25. Nikoobakht, B., El-Sayed, M. A. Preparation and growth mechanism of gold nanorods (NRs) using seed-mediated growth method. Chem. Mater. 15 (10), 1957-1962 (2003).
  26. Ratto, F., Matteini, P., Rossi, F., Pini, R. Size and shape control in the overgrowth of gold nanorods. J. Nanopart. Res. 12 (6), 2029-2036 (2009).
  27. Niidome, T., et al. PEG-modified gold nanorods with a stealth character for in vivo applications. J. Control. Release. 114 (3), 343-347 (2006).
  28. Tatini, F., et al. Size dependent biological profiles of PEGylated gold nanorods. J. Mater. Chem. B. 2, 6072-6080 (2014).
  29. Matteini, P., Ratto, F., Rossi, F., Centi, S., Dei, L., Pini, R. Chitosan films doped with gold nanorods as laser-activatable hybrid bioadhesives. Adv. Mater. 22 (38), 4313-4316 (2010).
  30. Matteini, P., Ratto, F., Rossi, F., de Angelis, M., Cavigli, L., Pini, R. Hybrid nanocomposite films for laser-activated tissue bonding. J. Biophotonics. 5 (11-12), 868-877 (2012).
  31. Matteini, P., Tatini, F., Cavigli, L., Ottaviano, S., Ghini, G., Pini, R. Graphene as a photothermal switch for controlled drug release. Nanoscale. 6, 7947-7953 (2014).
  32. Ratto, F., Witort, E., et al. Plasmonic Particles that Hit Hypoxic Cells. Adv. Funct. Mater. 25 (2), 316-323 (2015).
  33. Chithrani, D. B. Intracellular uptake, transport, and processing of gold nanostructures. Molec. Membrane Biol. 27 (7), 299-311 (2010).
  34. Mitchem, J. B., et al. Targeting tumor-infiltrating macrophages decreases tumor-initiating cells, relieves immunosuppression, and improves chemotherapeutic responses. Cancer Res. 73 (3), 1128-1141 (2013).
  35. Mantovani, A., Allavena, P. The interaction of anticancer therapies with tumor-associated macrophages. J. Exp. Med. 212 (4), 435-445 (2015).
  36. Panni, R. Z., Linehan, D. C., DeNardo, D. G. Targeting tumor-infiltrating macrophages to combat cancer. Immunotherapy. 5 (10), 1075-1087 (2013).
  37. Oh, E., et al. Cellular uptake and fate of PEGylated gold nanoparticles is dependent on both cell-penetration peptides and particle size. ACS Nano. 5 (8), 6434-6448 (2011).
  38. Yuan, H., Fales, A. M., Vo-Dinh, T. TAT peptide-functionalized gold nanostars: Enhanced intracellular delivery and efficient NIR photothermal therapy using ultralow irradiance. J. Am. Chem. Soc. 134 (28), 11358-11361 (2012).
  39. Ladest, S., Fales, A. M., Domard, A. Multi-membrane hydrogels. Nature. 452, 76-79 (2008).
  40. Matteini, P., et al. Photothermally activated hybrid films for quantitative confined release of chemical species. Angew. Chem. Int. Ed. (English). 52, 5956-5960 (2013).
  41. Khor, E., Lim, L. Y. Implantable applications of chitin and chitosan. Biomaterials. 24 (13), 2339-2349 (2003).
  42. Kennedy, L. C., et al. T cells enhance gold nanoparticle delivery to tumors in vivo. Nanoscale Res. Lett. 6 (1), 283(2011).
  43. Pissuwan, D., Valenzuela, S. M., Killingsworth, M. C., Xu, X., Cortie, M. B. Targeted destruction of murine macrophage cells with bioconjugated gold nanorods. J. Nanopart. Res. 9 (6), 1109-1124 (2007).
  44. Jokerst, J. V., Thangaraj, M., Kempen, P. J., Sinclair, R., Gambhir, S. S. Photoacoustic imaging of mesenchymal stem cells in living mice via silica-coated gold nanorods. ACS Nano. 6 (7), 5920-5930 (2012).
  45. Ding, H., et al. Gold nanorods coated with multilayer polyelectrolyte as contrast agents for multimodal imaging. J. Phys. Chem. C. 111 (34), 12552-12557 (2007).
  46. Esposito, G., et al. et al. In vivo laser assisted microvascular repair and end-to-end anastomosis by means of indocyanine green-infused chitosan patches: A pilot study. Lasers Surg. Med. 45 (5), 318-325 (2013).

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Tumor Associated MacrophagesPEGylated Gold NanorodsChitosan HydrogelPhotoacoustic MicroscopyPlasmonic ParticlesEndocytic VesiclesReshaping Threshold
Preparation and Photoacoustic Analysis of Cellular Vehicles Containing Gold Nanorods
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