Tailoring the SWIR emission of gold nanoclusters by surface ligand rigidification and their application in 3D bioimaging

The influence of solvent polarity and surface ligand rigidification on the SWIR emission profile of gold nanoclusters with an anistropic surface was investigated. A strong enhancement of the SWIR emission band at 1200 nm was observed when measuring in different local environments: in solution, in polymer composites, and in solids. SWIR in vivo imaging of mice assisted by deep learning after intravenous administration of these gold nanoclusters provides high definition pseudo-3D views of vascular blood vessels.

3D-printed scaffold combined to 2D osteoinductive coatings to repair a critical-size mandibular bone defect

The reconstruction of large bone defects (12 cm³) remains a challenge for clinicians. We developed a new critical-size mandibular bone defect model on a minipig, close to human clinical issues. We analyzed the bone reconstruction obtained by a 3D-printed scaffold made of clinical-grade polylactic acid (PLA), coated with a polyelectrolyte film delivering an osteogenic bioactive molecule (BMP-2). We compared the results (computed tomography scans, microcomputed tomography scans, histology) to the gold standard solution, bone autograft. We demonstrated that the dose of BMP-2 delivered from the scaffold significantly influenced the amount of regenerated bone and the repair kinetics, with a clear BMP-2 dose-dependence. Bone was homogeneously formed inside the scaffold without ectopic bone formation. The bone repair was as good as for the bone autograft. The BMP-2 doses applied in our study were reduced 20- to 75-fold compared to the commercial collagen sponges used in the current clinical applications, without any adverse effects. Three-dimensional printed PLA scaffolds loaded with reduced doses of BMP-2 may be a safe and simple solution for large bone defects faced in the clinic.

Electrochemotherapy guided by intraoperative fluorescence imaging for the treatment of inoperable peritoneal micro-metastases

Surgery is often the first therapeutic indication in cancer. Patient survival essentially depends on the completeness of tumor resection. This is a major challenge, particularly in patients with peritoneal carcinomatosis (PC), where tumors are widely disseminated in the large peritoneal cavity. These small tumors can be difficult to visualize and are often positioned in delicate locations, further increasing the risk of producing serious tissue/organ damage during their ablation. We propose an innovative therapeutic approach based on intraoperative fluorescence (IF) guided electrochemotherapy (ECT) for the treatment of peritoneal micro-metastases. ECT combines the effects of tissue electro-permeabilization (EP) with the administration of an antimitotic agent (bleomycin) that has poor permeability across intact membranes. IF significantly improves the detection of small tumor lesions. ECT is clinically validated for the treatment of cutaneous tumors in animals and humans, but this is the first time that it has been used along with IF imaging for the targeted treatment of peritoneal metastases in a preclinical model. We set up a murine model of PC that develops secondarily to the resection of a distant primary tumor. Tumor growth and metastasis were finely monitored by non-invasive multimodal imaging (bioluminescence and 3D fluorescence/microCT). Once metastases were detected, mice were randomized into three groups: the ECT group (bleomycin injected intravenously followed by EP) and 2 control groups (bleomycin alone and EP alone). Twenty four hours after the intravenous injection of the tumor targeting agent Angiostamp™700, mice in all groups underwent an abdominal surgery for metastases exploration assisted by fluorescence imaging with the Fluobeam®700 portative device. EP was applied to every nodule detected by IF, except in the bleomycin control group. After surgery, the metastatic invasion was tracked by bioluminescence imaging. In mice treated with bleomycin or EP alone, the metastatic load progressed very rapidly and mice showed no significant difference in lifespan compared to non-operated mice (median lifespan: 27days vs. 25days, respectively). In contrast, the mice treated with ECT displayed a decreased metastatic load and an increased survival rate (median lifespan: 34days). These results provide evidence that IF guided ECT is an effective approach for the treatment of inoperable intraperitoneal micro-metastases.

Optical small animal imaging in the drug discovery process

Molecular imaging of tumors in preclinical models is of the utmost importance for developing innovative cancer treatments. This field is moving extremely rapidly, with recent advances in optical imaging technologies and sophisticated molecular probes for in vivo imaging. The aim of this review is to provide a succinct overview of the imaging modalities available for rodents and with focus on describing optical probes for cancer imaging.

Intraoperative near-infrared image-guided surgery for peritoneal carcinomatosis in a preclinical experimental model

Background

This study compared the quality of surgery performed under conventional light with near-infrared (NIR) image-guided surgery using a tumour-targeting probe and a portable clinical grade imaging device in a mouse model of peritoneal carcinomatosis.

Methods

Peritoneal carcinomatosis was induced by injection of luciferase-positive tumour cells, leading to the formation of small nodules in the peritoneal cavity. One day after intravenous injection of RAFT-c(RGDfK)4-Alexa Fluor® 700, a fluorescent tumour-targeting probe, the surgeon operated using the Fluobeam®, a portable device that illuminated the mouse with NIR light and allowed NIR vision. The quality of the surgery was evaluated using bioluminescence, a highly sensitive method that detected the remaining tumour cells, and operating time was measured.

Results

Under normal light, the surgeon detected and removed a mean(s.d.) of only 50·6(2·3) per cent of the nodules that were visible under NIR light. The duration of surgery was reduced from 19·5(3·3) min under normal light to 14·0(2·6) min when NIR light was used (P = 0·025). The sensitivity of the NIR system allowed the detection of nodules containing as few as 227 tumour cells.

Conclusion

NIR image-guided surgery improved the quality of surgery for peritoneal carcinomatosis by doubling the number of nodules detected and significantly reducing the duration of surgery.

Drug development in oncology assisted by noninvasive optical imaging

Early and accurate detection of tumors, like the development of targeted treatments, is a major field of research in oncology. The generation of specific vectors, capable of transporting a drug or a contrast agent to the primary tumor site as well as to the remote (micro-) metastasis would be an asset for early diagnosis and cancer therapy. Our goal was to develop new treatments based on the use of tumor-targeted delivery of large biomolecules (DNA, siRNA, peptides, or nanoparticles), able to induce apoptosis while dodging the specific mechanisms developed by tumor cells to resist this programmed cell death. Nonetheless, the insufficient effectiveness of the vectorization systems is still a crucial issue. In this context, we generated new targeting vectors for drug and biomolecules delivery and developed several optical imaging systems for the follow-up and evaluation of these vectorization systems in live mice. Based on our recent work, we present a brief overview of how noninvasive optical imaging in small animals can accelerate the development of targeted therapeutics in oncology.

Improving the detection of osteosarcoma tumor margins and metastasis using diagnostic nanoparticles

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Background: The aim of osteosarcoma resection is the complete removal of the primary malignant lesion with adequate margins taking into account tumor control and functional reconstruction. To date, no intraoperative method is available to assist surgeons in precisely delineating tumor extension in the adjacent normal tissues. Thus, preoperative imaging and extended surgical resection remains the gold standard. We developed fluorescent nanoparticles RAFT-cRGD4-ICG’ targeting αVβ3 integrins on tumor neovessels and demonstrated their capacity to reveal tumor and its margins when exposed to near infrared (NIR) light. Methods: We evaluated in an orthotopic metastatic osteosarcoma in rats the potential of RAFT-cRGD4-ICG’ detected intra operatively by NIR illumination to improve margin resection without compromising local tumor control. Controls consisted of pathological margin analysis of the resected tumor/metastasis comparing ICG’ fluorescence with conventional tissue coloration, and pre operative magnetic resonance imaging. Results: We showed a significantly lesser extent of healthy tissue resection after surgical excision when assessing tumor margin intra operatively using RAFT-cRGD4-ICG’ and NIR camera compared to preoperative imaging studies and post operative conventional pathology coloration (p<0.01). Importantly, intraoperative NIR illumination of lungs revealed more metastases than by intraoperative manual lung palpation (p<0.01). Conclusions: Our preclinical data confirm the potential of intraoperative imaging for improved primary tumor and lung metastasis excision. We are now generating clinical-grade RAFT-cRGD4-ICG’ to further evaluate this approach as a mean to improve functional outcome after surgical excision while maintaining tumor control in patients with relapsed/metastatic osteosarcoma.

No significant financial relationships to disclose.

Non-invasive in vivo optical imaging of the lacZ and luc gene expression in mice

The bacterial lacZ gene encoding for beta-galactosidase (beta-gal) is a common reporter gene used in transgenic mice. Nonetheless, the absence of fluorigenic substrates usable in live animals greatly hampered the non-invasive follow-up of this reporter gene expression. We used far-red fluorescence for imaging beta-Gal expression in live cells in vitro or in vivo. The 9H-(1,3-dichloro-9,9-dimethylacridin- 2-one-7-yl) beta-D-galactopyranoside substrate was used to monitor beta-Gal expression as a reporter of tumor growth, or of the physiological levels of an endogenous gene or of gene transfer in lung. A quantitative evaluation of this method as well as a comparison of its sensitivity with Firefly Luciferase-based bioluminescence was also performed. In vivo measurements showed that 10(3) beta-Gal tumor cells located under the skin were detectable. In deeper organs like lung, as little as 5 ng of beta-Gal or Luciferase enzymes per mg of proteins were measured, confirming that both techniques reached similar sensibilities. Nonetheless, quantitative comparison of beta-Gal levels measured with far-red imaging or with a standardized enzymatic evaluation after killing revealed that the 2D-fluorescent reflectance imaging method is submitted to a color-dependent disparity of the organs and cannot supply quantitative measurements but that a simple correction can be applied.