Research Highlights For reprint orders, please contact: [email protected]
Highlights from the latest research in nanomedicine
A nanoparticulate hydrogel anticancer vaccine Evaluation of: Muraoka D, Harada N, Hayashi T et al. Nanogel-based immunologically stealth vaccine targets macrophages in the medulla of lymph node and induces potent antitumor immunity. ACS Nano 8(9), 9209–9218 (2014). Therapeutic cancer vaccines are designed to stimulate highly specific immune responses against cancers by targeting tumor-associated antigens. Various vaccines have utilized a wide range of immunogenic agents, including peptides, recombinant viruses, tumor cells and primed antigen-presenting dendritic cells, in combination with immunogenicityboosting adjuvants, immune suppression inhibitors or traditional chemotherapeutic agents [1] . However, cancer vaccines have been of varying effectiveness in clinical trials due to tumor characteristics such as antigenic heterogeneity and immunosuppressive mechanisms. Antigenic heterogeneity may allow the tumors to develop resistance against single-target immunogenic agents, while immunosuppressive mechanisms reduce the effectiveness of the immune response and alter the self-recognition mechanisms, causing cancerous cells to be ignored. Furthermore, tumor-associated antigen-targeting agents show varying immunogenic properties, with tradeoffs between specificity and effectiveness [1–3] . Nanoparticles have been of interest as efficacy-enhancing vaccine delivery agents due to their size and customizability. They are small enough to move into lymphatic systems and enter antigen-presenting cells through engulfment, and can be designed for specific
10.2217/NNM.14.208 © 2015 Future Medicine Ltd
parameters in terms of shape, surface properties and composition in order to enable antigen delivery specificity and presentation longevity [4,5] . Muraoka et al. developed hydrogel nanoparticles (nanogels) of approximately 50 nm in diameter using cholesteryl pullulan (CHP) polysaccharides, which self-assemble in water. These nanogels stably complex with polypeptides through hydrophobic interactions. Stability was shown for over 40 h in serum using nanogels complexed with a long-peptide antigen (LPA,) which either included the murine tumor-specific antigen mERK2 or the human tumor antigen MAGE-A4. Due to their small particle size, lack of charge and potential ligand sites, the CHP–LPA nanogel complexes travel efficiently in the lymphatic system to the draining lymph node, escaping uptake by lymph node dendritic cells until they reach the central medulla portion of the node. There, they are largely engulfed by medullary macrophages. Cellular uptake was evaluated through flow cytometry assessments of rhodamine-labeled CHP nanogels upon immune cell populations isolated from the draining lymph node. LPA that was complexed with other formulations did not show similar uptake patterns. Medullary macrophage antigen cross-presentation was assessed with CHP–mERK2 LPA, a Toll-like receptor 9 agonist and a CpG oligodeoxynucleotide adjuvant. The results showed successful T-cell recognition of mERK2-derived tumor epitopes mainly with the macrophage cells purified from the lymph nodes, with weak T-cell responses from purified dendritic cell populations. These outcomes were confirmed by impaired
Nanomedicine (Lond.) (2015) 10(1), 5–8
Sophie L Wang1, Upendra Chitgupi1 & Jonathan F Lovell*,1 Department of Biomedical Engineering, University at Buffalo, State University of New York, Buffalo, NY 14260, USA *Author for correspondence: [email protected] 1
part of
ISSN 1743-5889
5
Research Highlights Wang, Chitgupi & Lovell T-cell responses when macrophage knockouts were performed using clodronate liposomes. The researchers then assessed therapeutic vaccine activity by comparing the CHP–LPA complexes with a conventional vaccine delivery system using LPA emulsified in incomplete Freund’s adjuvant (IFA). In a prophylactic setting, the CHP–LPA complexes showed greater effectiveness than the IFA–LPA system for inhibiting tumor growth. In the therapeutic setting, only the CHP–LPA complex significantly suppressed tumor growth (the IFA–LPA system did not affect tumor growth). This study shows interesting results in both the development of an effective prophylactic and therapeutic anticancer vaccine system, along with the elucidation of the potentially important role of medullary macrophages in T-cell responses. Jumpstart my golden nanoparticle heart Evaluation of: Shevach M, Fleischer S, Shapira A, Dvir T. Gold nanoparticle-decellularized matrix hybrids for cardiac tissue engineering. Nano Lett. 14(10), 5792–5796 (2014). Myocardial infarction preceding heart failure is the leading cause of death worldwide [6] . Tissue engineering offers intriguing possibilities for treatments since myocardial tissue cannot otherwise regenerate completely after myocardial infarction. Cardiac patch engineering involves developing a biocompatible 3D scaffold that can be transplanted to the site of repair, without generating an immunogenic response. One of the challenges with respect to cardiac tissue engineering is to overcome the creation of slow and inefficient electrical couplings between adjacent cells, which can impair the process of tissue regeneration [7] . In this article, the authors developed a novel goldbased hybrid 3D scaffold that can successfully function as a cardiac patch. The authors have laid out a framework so that omental tissue (found in abundance in the abdominal cavity) harvested from a patient’s body can be rendered nonimmunogenic by decellurization in order to make an autologous porous 3D scaffold for transplantation back into the patient. For this study, the authors used a system in which rat cardiomyocytes were seeded in a hybrid scaffold derived from omental tissues derived from pigs. The conductivity of the decellularized scaffold was enhanced by integrating gold nanoparticles (4 and 10 nm) using an electron beam evaporator. One major parameter that was quantified was the engineered tissue’s electrical conductivity. The results showed that the hybrid gold scaffolds offered electrical conductivity levels that were several-fold higher than those of the control scaffold. The stability of the
6
Nanomedicine (Lond.) (2015) 10(1)
scaffolds and the retention of gold nanoparticles by the scaffolds were essential for their proper function. The scaffolds proved to be stable and showed that the gold content of the fibers was preserved even after 7 days. To evaluate the organization of the tissue on the scaffold, cardiac patches were stained for α-sarcomeric actinin and connexin-43, which are important proteins associated with contraction and electrical coupling, respectively. One of the key design considerations in cardiac tissue engineering is maintaining a balance between contracting cardiomyocytes and highly proliferative noncontracting fibroblasts. In myocardial infarction, the remodeling of the heart matrix leads to an increase in fibroblasts. There were concerns that the gold nanoparticles might alter the ratio of fibroblasts to cardiomyocytes. Hence, the researchers investigated the effects of the gold nanoparticles in their hybrid scaffold on fibroblast proliferation through the staining and quantification of specific cell type markers. The researchers successfully fabricated a hybrid bioinspired scaffold with gold nanoparticles for cardiac patch tissue engineering. Similar work has been conducted using nanowires on 3D scaffolds, and the literature shows that various nanotechnologies hold great potential for cardiac patch tissue engineering [8,9] . By employing gold nanoparticles, these authors enhanced conductivity, thereby engineering a functionally and mechanically stable cardiac patch. The proposed concept of using native tissue and cardiomyocytes from the patient to develop an autologous scaffold that would be tailor-made for an individual greatly reduces the risk of immune rejection. In future, the same technique could be used in the regeneration of other cell types. siRNA treatment of Marburg virus Evaluation of: Thi EP, Mire CE, Ursic-Bedoya R et al. Marburg virus infection in nonhuman primates: therapeutic treatment by lipid-encapsulated siRNA. Sci. Transl. Med. 6(250), 250ra116 (2014). Marburg virus (MARV) belongs to Filoviridae, the taxonomic family of filamentous viruses that encodes genetic information in single-stranded, nonsegmented, negative-sense RNA. Ebola virus (EBOV), a related virus that is currently highly visible in the public consciousness, belongs to the same family. Filoviruses tend to cause fatal hemorrhagic fevers in humans and nonhuman primates in outbreaks, with human fatality rates as high as 90%. Due to their deadliness, a lack of countermeasures and vaccines and a history of usage in biological weapons programs, filoviruses are classified as tier 1 select agents and category A priority pathogens by US government agencies. Transmission is typically through exposure to direct contact with infected bodily fluids
future science group
Highlights from the latest research in nanomedicine
such as blood, saliva, mucus secretions, tissue and stool. Bats are suspected of being a viral reservoir for MARV, with some evidence for them being carriers of EBOV as well [10–12] . Previous animal studies of various filovirus vaccines have shown success against EBOV when the subjects were prophylactically treated before viral exposure or therapeutically treated within 3 days after infection detection. However, results in MARV have been less substantial, with studies focusing on treatment against exposure rather than therapeutic treatment. Furthermore, the vaccines tested were on varying and less pathogenic strains of MARV, with little evidence of protection against all strains of MARV. Here, the authors present a nonvaccine-based strategy for treating the virus using RNAi. Thi et al. assessed the efficacy of the lipid nanoparticle (LNP) delivery of siRNA targeted against the highly conserved MARV nucleoprotein (NP-718m-LNP) by challenging 21 rhesus monkeys with lethal doses of the most pathogenic viral strain, MARV-Angola. The infection control group had no treatment and the nontargeted LNP control group was treated with LNPs delivering siRNA targeting a nonspecific gene, firefly luciferase (Luc-LNP). The treatment time points with NP-718m-LNP were from 30–45 min to 72 h after infection. The treatments were daily bolus intravenous doses. The results showed that for the animals treated with NP-718-LNP, viral load was effectively reduced, clinical symptoms were milder and all treated animals survived, unlike with the controls, where all of the animals succumbed to the disease 7–9 days after infection. Despite the caveats of this small-scale study, the results were highly indicative of therapeutic effectiveness. The targeting of a highly conserved viral region holds promise of being universally protective, along with being generalizable to other filoviruses, such as EBOV. A new window into the brain Evaluation of: Hong G, Diao S, Chang J et al. Through-skull fluorescence imaging of the brain through a new near-infrared window. Nat. Phot. 8(9), 723–730 (2014). Magnetic resonance angiography and x-ray computed tomography have been the best methods for brain imaging to date, with limiting factors including spatial resolution (submillimeter) and long scanning times (minutes) leading to poor resolution of small vessels and dynamic blood flow [13,14] . In vivo methods, such as craniotomies, cranial windows and skull-thinning techniques [15] , facilitate fluorescence-based techniques that are hampered by a lack of penetration depth, thereby affecting the spatial resolution of the images.
future science group
Research Highlights
To improve optical imaging techniques, fluorescence imaging was investigated in three spectra ranges of the near infrared (NIR): the NIR-I (750–900 nm), the NIR-IIa (1300–1400 nm) and the broader NIR-II (1000–1700 nm) windows. The authors reported the use of single-walled nanotube (SWNT)–IRDye800 conjugates as a fluorescence contrast agent for the in vivo imaging of the brain. Photon scattering was minimal in the NIRIIa window, which is ideal for in vivo imaging, since reduced scattering greatly enhances in vivo imaging. The authors employed the use of high-pressure CO conversion SWNT–IRDye800 dye conjugates [16] , which both can be excited at 808 nm, facilitating their use as emitters of fluorescence in the NIR-I, NIR-II and NIR-IIa ranges, which proved advantageous for studying all three infrared regions in parallel. The researchers conducted live mouse imaging and the results showed that the background signals and vessel blurriness were reduced by using the NIR-IIa window. Sharper and higher-resolution images of the brain vessels were seen in the NIR-IIa region, supporting the fundamental premise. The authors further studied hemodynamics and perfusion in a middle cerebral artery occlusion (MCAO) mouse model. When the SWNT–IRDye800 conjugate was injected into a mouse with surgically induced MCAO, the left hemisphere with MCAO showed a delay in blood flow and the right hemisphere exhibited blood flow that was the same as that of the control mouse. One of the major successes of this study is that it could track blood flow in a wide field imaging setup, thus making it feasible to track the flow of blood in different vessels at the same time. In conclusion, the researchers’ technique of NIR-IIa imaging of SWNT–IRDye800 conjugates facilitated the noninvasive imaging of the brain capillary vessel anatomy and function with excellent spatial resolution and penetration depth. Further study on the toxicity, accumulation and metabolism of the fluorophore conjugate is warranted. The authors have conducted a commendable work in spectacular noninvasive brain imaging using an underexplored, biologically transparent optical spectral window. Financial & competing interests disclosure The authors have no relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript. This includes employment, consultancies, honoraria, stock ownership or options, expert testimony, grants or patents received or pending, or royalties. No writing assistance was utilized in the production of this manuscript.
www.futuremedicine.com
7
Research Highlights Wang, Chitgupi & Lovell References
8
10
Bradfute SB, Dye JM, Bavari S. Filovirius vaccines. Hum. Vaccin. 7(6), 701–711 (2011).
1
Schlom J. Therapeutic cancer vaccines: current status and moving forward. J. Natl Cancer Inst. 104(8), 599–613 (2012).
11
2
Palucka K, Ueno H, Banchereau J. Recent developments in cancer vaccines. J. Immunol. 186(3), 1325–1331 (2011).
Falzarano D. Progress in filovirus vaccine development: evaluating the potential for clinical use. Expert Rev. Vaccines. 10(1), 63–77 (2011).
12
3
Palucka K, Banchereau J. Dendritic-cell-based therapeutic cancer vaccines. Immunity 39(1), 38–48 (2013).
Thi EP, Mire CE, Ursic-Bedoya R et al. Marburg virus infection in nonhuman primates: therapeutic treatment by lipid-encapsulated siRNA. Sci. Transl. Med. 6(250), 250ra116 (2014).
4
Zhao L, Seth A, Wibowo N et al. Nanoparticle vaccines. Vaccine 32(3), 327–337 (2014).
13
5
Gregory AE, Titball R, Williamson D. Vaccine delivery using nanoparticles. Front. Cell. Infect. Microbiol. 3, 13 (2013).
Wright SN, Kochunov P, Mut F et al. Digital reconstruction and morphometric analysis of human brain arterial vasculature from magnetic resonance angiography. Neuroimage 8(0), 170–181 (2013).
14
6
Lloyd-Jones D, Adams RJ, Brown TM et al. Executive summary: heart disease and stroke statistics – 2010 update: a report from the American Heart Association. Circulation 121(7), 948–954 (2010).
Paulus MJ, Gleason SS, Kennel SJ, Hunsicker PR, Johnson DK. High resolution x-ray computed tomography: an emerging tool for small animal cancer research. Neoplasia 2(1–2), 62–70 (2000).
15
7
Shevach M, Fleischer S, Shapira A, Dvir T. Gold nanoparticle-decellularized matrix hybrids for cardiac tissue engineering. Nano Lett. 14(10), 5792–5796 (2014).
Yang G, Pan F, Parkhurst CN, Grutzendler J, Gan W-B. Thinned-skull cranial window technique for long-term imaging of the cortex in live mice. Nat. Protoc. 5(2), 201–208 (2010).
8
Dvir T, Timko B, Brigham M. Nanowired three-dimensional cardiac patches. Nat. Nanotechnol. 6(11), 720–725 (2011).
16
9
Dvir T, Timko BP, Kohane DS, Langer R. Nanotechnological strategies for engineering complex tissues. Nat. Nanotechnol. 6(1), 13–22 (2011).
Chiang IW, Brinson BE, Huang a. Y et al. Purification and characterization of single-wall carbon nanotubes (SWNTs) obtained from the gas-phase decomposition of CO (HiPco process). J. Phys. Chem. B 105(35), 8297–8301 (2001).
Nanomedicine (Lond.) (2015) 10(1)
future science group
Highlights from the latest research in nanomedicine
A nanoparticulate hydrogel anticancer vaccine Evaluation of: Muraoka D, Harada N, Hayashi T et al. Nanogel-based immunologically stealth vaccine targets macrophages in the medulla of lymph node and induces potent antitumor immunity. ACS Nano 8(9), 9209–9218 (2014). Therapeutic cancer vaccines are designed to stimulate highly specific immune responses against cancers by targeting tumor-associated antigens. Various vaccines have utilized a wide range of immunogenic agents, including peptides, recombinant viruses, tumor cells and primed antigen-presenting dendritic cells, in combination with immunogenicityboosting adjuvants, immune suppression inhibitors or traditional chemotherapeutic agents [1] . However, cancer vaccines have been of varying effectiveness in clinical trials due to tumor characteristics such as antigenic heterogeneity and immunosuppressive mechanisms. Antigenic heterogeneity may allow the tumors to develop resistance against single-target immunogenic agents, while immunosuppressive mechanisms reduce the effectiveness of the immune response and alter the self-recognition mechanisms, causing cancerous cells to be ignored. Furthermore, tumor-associated antigen-targeting agents show varying immunogenic properties, with tradeoffs between specificity and effectiveness [1–3] . Nanoparticles have been of interest as efficacy-enhancing vaccine delivery agents due to their size and customizability. They are small enough to move into lymphatic systems and enter antigen-presenting cells through engulfment, and can be designed for specific
10.2217/NNM.14.208 © 2015 Future Medicine Ltd
parameters in terms of shape, surface properties and composition in order to enable antigen delivery specificity and presentation longevity [4,5] . Muraoka et al. developed hydrogel nanoparticles (nanogels) of approximately 50 nm in diameter using cholesteryl pullulan (CHP) polysaccharides, which self-assemble in water. These nanogels stably complex with polypeptides through hydrophobic interactions. Stability was shown for over 40 h in serum using nanogels complexed with a long-peptide antigen (LPA,) which either included the murine tumor-specific antigen mERK2 or the human tumor antigen MAGE-A4. Due to their small particle size, lack of charge and potential ligand sites, the CHP–LPA nanogel complexes travel efficiently in the lymphatic system to the draining lymph node, escaping uptake by lymph node dendritic cells until they reach the central medulla portion of the node. There, they are largely engulfed by medullary macrophages. Cellular uptake was evaluated through flow cytometry assessments of rhodamine-labeled CHP nanogels upon immune cell populations isolated from the draining lymph node. LPA that was complexed with other formulations did not show similar uptake patterns. Medullary macrophage antigen cross-presentation was assessed with CHP–mERK2 LPA, a Toll-like receptor 9 agonist and a CpG oligodeoxynucleotide adjuvant. The results showed successful T-cell recognition of mERK2-derived tumor epitopes mainly with the macrophage cells purified from the lymph nodes, with weak T-cell responses from purified dendritic cell populations. These outcomes were confirmed by impaired
Nanomedicine (Lond.) (2015) 10(1), 5–8
Sophie L Wang1, Upendra Chitgupi1 & Jonathan F Lovell*,1 Department of Biomedical Engineering, University at Buffalo, State University of New York, Buffalo, NY 14260, USA *Author for correspondence: [email protected] 1
part of
ISSN 1743-5889
5
Research Highlights Wang, Chitgupi & Lovell T-cell responses when macrophage knockouts were performed using clodronate liposomes. The researchers then assessed therapeutic vaccine activity by comparing the CHP–LPA complexes with a conventional vaccine delivery system using LPA emulsified in incomplete Freund’s adjuvant (IFA). In a prophylactic setting, the CHP–LPA complexes showed greater effectiveness than the IFA–LPA system for inhibiting tumor growth. In the therapeutic setting, only the CHP–LPA complex significantly suppressed tumor growth (the IFA–LPA system did not affect tumor growth). This study shows interesting results in both the development of an effective prophylactic and therapeutic anticancer vaccine system, along with the elucidation of the potentially important role of medullary macrophages in T-cell responses. Jumpstart my golden nanoparticle heart Evaluation of: Shevach M, Fleischer S, Shapira A, Dvir T. Gold nanoparticle-decellularized matrix hybrids for cardiac tissue engineering. Nano Lett. 14(10), 5792–5796 (2014). Myocardial infarction preceding heart failure is the leading cause of death worldwide [6] . Tissue engineering offers intriguing possibilities for treatments since myocardial tissue cannot otherwise regenerate completely after myocardial infarction. Cardiac patch engineering involves developing a biocompatible 3D scaffold that can be transplanted to the site of repair, without generating an immunogenic response. One of the challenges with respect to cardiac tissue engineering is to overcome the creation of slow and inefficient electrical couplings between adjacent cells, which can impair the process of tissue regeneration [7] . In this article, the authors developed a novel goldbased hybrid 3D scaffold that can successfully function as a cardiac patch. The authors have laid out a framework so that omental tissue (found in abundance in the abdominal cavity) harvested from a patient’s body can be rendered nonimmunogenic by decellurization in order to make an autologous porous 3D scaffold for transplantation back into the patient. For this study, the authors used a system in which rat cardiomyocytes were seeded in a hybrid scaffold derived from omental tissues derived from pigs. The conductivity of the decellularized scaffold was enhanced by integrating gold nanoparticles (4 and 10 nm) using an electron beam evaporator. One major parameter that was quantified was the engineered tissue’s electrical conductivity. The results showed that the hybrid gold scaffolds offered electrical conductivity levels that were several-fold higher than those of the control scaffold. The stability of the
6
Nanomedicine (Lond.) (2015) 10(1)
scaffolds and the retention of gold nanoparticles by the scaffolds were essential for their proper function. The scaffolds proved to be stable and showed that the gold content of the fibers was preserved even after 7 days. To evaluate the organization of the tissue on the scaffold, cardiac patches were stained for α-sarcomeric actinin and connexin-43, which are important proteins associated with contraction and electrical coupling, respectively. One of the key design considerations in cardiac tissue engineering is maintaining a balance between contracting cardiomyocytes and highly proliferative noncontracting fibroblasts. In myocardial infarction, the remodeling of the heart matrix leads to an increase in fibroblasts. There were concerns that the gold nanoparticles might alter the ratio of fibroblasts to cardiomyocytes. Hence, the researchers investigated the effects of the gold nanoparticles in their hybrid scaffold on fibroblast proliferation through the staining and quantification of specific cell type markers. The researchers successfully fabricated a hybrid bioinspired scaffold with gold nanoparticles for cardiac patch tissue engineering. Similar work has been conducted using nanowires on 3D scaffolds, and the literature shows that various nanotechnologies hold great potential for cardiac patch tissue engineering [8,9] . By employing gold nanoparticles, these authors enhanced conductivity, thereby engineering a functionally and mechanically stable cardiac patch. The proposed concept of using native tissue and cardiomyocytes from the patient to develop an autologous scaffold that would be tailor-made for an individual greatly reduces the risk of immune rejection. In future, the same technique could be used in the regeneration of other cell types. siRNA treatment of Marburg virus Evaluation of: Thi EP, Mire CE, Ursic-Bedoya R et al. Marburg virus infection in nonhuman primates: therapeutic treatment by lipid-encapsulated siRNA. Sci. Transl. Med. 6(250), 250ra116 (2014). Marburg virus (MARV) belongs to Filoviridae, the taxonomic family of filamentous viruses that encodes genetic information in single-stranded, nonsegmented, negative-sense RNA. Ebola virus (EBOV), a related virus that is currently highly visible in the public consciousness, belongs to the same family. Filoviruses tend to cause fatal hemorrhagic fevers in humans and nonhuman primates in outbreaks, with human fatality rates as high as 90%. Due to their deadliness, a lack of countermeasures and vaccines and a history of usage in biological weapons programs, filoviruses are classified as tier 1 select agents and category A priority pathogens by US government agencies. Transmission is typically through exposure to direct contact with infected bodily fluids
future science group
Highlights from the latest research in nanomedicine
such as blood, saliva, mucus secretions, tissue and stool. Bats are suspected of being a viral reservoir for MARV, with some evidence for them being carriers of EBOV as well [10–12] . Previous animal studies of various filovirus vaccines have shown success against EBOV when the subjects were prophylactically treated before viral exposure or therapeutically treated within 3 days after infection detection. However, results in MARV have been less substantial, with studies focusing on treatment against exposure rather than therapeutic treatment. Furthermore, the vaccines tested were on varying and less pathogenic strains of MARV, with little evidence of protection against all strains of MARV. Here, the authors present a nonvaccine-based strategy for treating the virus using RNAi. Thi et al. assessed the efficacy of the lipid nanoparticle (LNP) delivery of siRNA targeted against the highly conserved MARV nucleoprotein (NP-718m-LNP) by challenging 21 rhesus monkeys with lethal doses of the most pathogenic viral strain, MARV-Angola. The infection control group had no treatment and the nontargeted LNP control group was treated with LNPs delivering siRNA targeting a nonspecific gene, firefly luciferase (Luc-LNP). The treatment time points with NP-718m-LNP were from 30–45 min to 72 h after infection. The treatments were daily bolus intravenous doses. The results showed that for the animals treated with NP-718-LNP, viral load was effectively reduced, clinical symptoms were milder and all treated animals survived, unlike with the controls, where all of the animals succumbed to the disease 7–9 days after infection. Despite the caveats of this small-scale study, the results were highly indicative of therapeutic effectiveness. The targeting of a highly conserved viral region holds promise of being universally protective, along with being generalizable to other filoviruses, such as EBOV. A new window into the brain Evaluation of: Hong G, Diao S, Chang J et al. Through-skull fluorescence imaging of the brain through a new near-infrared window. Nat. Phot. 8(9), 723–730 (2014). Magnetic resonance angiography and x-ray computed tomography have been the best methods for brain imaging to date, with limiting factors including spatial resolution (submillimeter) and long scanning times (minutes) leading to poor resolution of small vessels and dynamic blood flow [13,14] . In vivo methods, such as craniotomies, cranial windows and skull-thinning techniques [15] , facilitate fluorescence-based techniques that are hampered by a lack of penetration depth, thereby affecting the spatial resolution of the images.
future science group
Research Highlights
To improve optical imaging techniques, fluorescence imaging was investigated in three spectra ranges of the near infrared (NIR): the NIR-I (750–900 nm), the NIR-IIa (1300–1400 nm) and the broader NIR-II (1000–1700 nm) windows. The authors reported the use of single-walled nanotube (SWNT)–IRDye800 conjugates as a fluorescence contrast agent for the in vivo imaging of the brain. Photon scattering was minimal in the NIRIIa window, which is ideal for in vivo imaging, since reduced scattering greatly enhances in vivo imaging. The authors employed the use of high-pressure CO conversion SWNT–IRDye800 dye conjugates [16] , which both can be excited at 808 nm, facilitating their use as emitters of fluorescence in the NIR-I, NIR-II and NIR-IIa ranges, which proved advantageous for studying all three infrared regions in parallel. The researchers conducted live mouse imaging and the results showed that the background signals and vessel blurriness were reduced by using the NIR-IIa window. Sharper and higher-resolution images of the brain vessels were seen in the NIR-IIa region, supporting the fundamental premise. The authors further studied hemodynamics and perfusion in a middle cerebral artery occlusion (MCAO) mouse model. When the SWNT–IRDye800 conjugate was injected into a mouse with surgically induced MCAO, the left hemisphere with MCAO showed a delay in blood flow and the right hemisphere exhibited blood flow that was the same as that of the control mouse. One of the major successes of this study is that it could track blood flow in a wide field imaging setup, thus making it feasible to track the flow of blood in different vessels at the same time. In conclusion, the researchers’ technique of NIR-IIa imaging of SWNT–IRDye800 conjugates facilitated the noninvasive imaging of the brain capillary vessel anatomy and function with excellent spatial resolution and penetration depth. Further study on the toxicity, accumulation and metabolism of the fluorophore conjugate is warranted. The authors have conducted a commendable work in spectacular noninvasive brain imaging using an underexplored, biologically transparent optical spectral window. Financial & competing interests disclosure The authors have no relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript. This includes employment, consultancies, honoraria, stock ownership or options, expert testimony, grants or patents received or pending, or royalties. No writing assistance was utilized in the production of this manuscript.
www.futuremedicine.com
7
Research Highlights Wang, Chitgupi & Lovell References
8
10
Bradfute SB, Dye JM, Bavari S. Filovirius vaccines. Hum. Vaccin. 7(6), 701–711 (2011).
1
Schlom J. Therapeutic cancer vaccines: current status and moving forward. J. Natl Cancer Inst. 104(8), 599–613 (2012).
11
2
Palucka K, Ueno H, Banchereau J. Recent developments in cancer vaccines. J. Immunol. 186(3), 1325–1331 (2011).
Falzarano D. Progress in filovirus vaccine development: evaluating the potential for clinical use. Expert Rev. Vaccines. 10(1), 63–77 (2011).
12
3
Palucka K, Banchereau J. Dendritic-cell-based therapeutic cancer vaccines. Immunity 39(1), 38–48 (2013).
Thi EP, Mire CE, Ursic-Bedoya R et al. Marburg virus infection in nonhuman primates: therapeutic treatment by lipid-encapsulated siRNA. Sci. Transl. Med. 6(250), 250ra116 (2014).
4
Zhao L, Seth A, Wibowo N et al. Nanoparticle vaccines. Vaccine 32(3), 327–337 (2014).
13
5
Gregory AE, Titball R, Williamson D. Vaccine delivery using nanoparticles. Front. Cell. Infect. Microbiol. 3, 13 (2013).
Wright SN, Kochunov P, Mut F et al. Digital reconstruction and morphometric analysis of human brain arterial vasculature from magnetic resonance angiography. Neuroimage 8(0), 170–181 (2013).
14
6
Lloyd-Jones D, Adams RJ, Brown TM et al. Executive summary: heart disease and stroke statistics – 2010 update: a report from the American Heart Association. Circulation 121(7), 948–954 (2010).
Paulus MJ, Gleason SS, Kennel SJ, Hunsicker PR, Johnson DK. High resolution x-ray computed tomography: an emerging tool for small animal cancer research. Neoplasia 2(1–2), 62–70 (2000).
15
7
Shevach M, Fleischer S, Shapira A, Dvir T. Gold nanoparticle-decellularized matrix hybrids for cardiac tissue engineering. Nano Lett. 14(10), 5792–5796 (2014).
Yang G, Pan F, Parkhurst CN, Grutzendler J, Gan W-B. Thinned-skull cranial window technique for long-term imaging of the cortex in live mice. Nat. Protoc. 5(2), 201–208 (2010).
8
Dvir T, Timko B, Brigham M. Nanowired three-dimensional cardiac patches. Nat. Nanotechnol. 6(11), 720–725 (2011).
16
9
Dvir T, Timko BP, Kohane DS, Langer R. Nanotechnological strategies for engineering complex tissues. Nat. Nanotechnol. 6(1), 13–22 (2011).
Chiang IW, Brinson BE, Huang a. Y et al. Purification and characterization of single-wall carbon nanotubes (SWNTs) obtained from the gas-phase decomposition of CO (HiPco process). J. Phys. Chem. B 105(35), 8297–8301 (2001).
Nanomedicine (Lond.) (2015) 10(1)
future science group
