Near-infrared Fluorescence Imaging Using a Protease-activatable Nanoprobe in Tumor Detection: Comparison with Narrow-band Imaging

BACKGROUND/AIMS: Advances in endoscopic technology seek to improve the accuracy of neoplastic tumor detection. Recently developed endoscopy devices such as narrow-band imaging (NBI) nevertheless have limitations in morphologic diagnosis. The purpose of this study was to investigate whether a novel imaging technique-near-infrared fluorescence (NIRF) imaging using a protease-activatable nanoprobe-could provide more accurate neoplastic tumor detection, compared to NBI. METHODS: Images of the intestines of Apc(Min/+) mice were obtained by NIRF using a matrix metalloproteinase (MMP)-sensing probe, which was based on a nanoparticle platform. Immediately after imaging, endoscopy with NBI capability was performed on the same excised intestine. Macroscopic and microscopic findings in the intestines were assessed, and MMP expression was analyzed by Western blotting and real-time polymerase chain reaction. RESULTS: Numerous tiny polypoid lesions were present in the intestines of aged Apc(Min/+) mice. These lesions included adenomas, lymphoid follicles, and protruding normal tissues. When using NIRF imaging with an MMP-activatable nanoprobe, adenomatous polyps showed higher fluorescence, compared to lymphoid follicles or adjacent normal tissues. The expression of MMP was higher in the adenomatous tissue than in the other tissues. The sensitivity and specificity for adenoma detection were 88.9% and 82.2%, respectively, when using NIRF imaging with a MMP-nanoprobe, compared to 77.8% and 66.7%, respectively, when using NBI (P<0.05). CONCLUSIONS: Near-infrared fluorescence imaging with a protease-activatable nanoprobe could aid in the differentiation of tumor characteristics. Clinical application of this approach may improve the endoscopic detection of neoplastic tumors.

Near-Infrared Fluorescence Imaging Using a Protease-Specific Probe for the Detection of Colon Tumors

BACKGROUND/AIMS: Early tumor detection is crucial for the prevention of colon cancer. Near-infrared fluorescence (NIRF) imaging using a target-activatable probe may permit earlier disease detection. Matrix metalloproteinases (MMPs) participate in tumorigenesis and tumor growth. The aim of this study was to determine whether NIRF imaging using an MMP-activatable probe can detect colon tumors at early stages. METHODS: We utilized two murine colon cancer models: a sporadic colon cancer model induced by azoxymethane (AOM), and a colitis-associated cancer model induced by a combination of AOM and dextran sodium sulfate (DSS). Colonic lesions were analyzed by histologic examination, Western blotting, immunohistochemical staining, and NIRF imaging using an MMP-activatable probe. RESULTS: Multiple variable-sized tumors developed in both models and progressed from adenomas to adenocarcinomas over time. At the early stage of the AOM/DSS model, diffuse inflammation was observed within the tumors. MMP expression increased progressively through normal, inflammation, adenoma, and adenocarcionoma stages. NIRF signal intensities were strongly correlated with each tumor stage from adenoma to adenocarcinoma. NIRF imaging also distinguished tumors from inflamed mucosa. CONCLUSIONS: NIRF imaging using a protease-activatable probe may be a useful tool for early tumor detection. This approach could translate to improve the endoscopic detection of colon tumors, especially in patients with inflammatory bowel disease.

Multifunctional Nanoparticles for Molecular Imaging

Molecular imaging is a bioimaging that can detect biochemically and genetically relevant events in molecular level in cells and tissues via quantitative imaging signal. Molecular imaging provides potential advantages to examine early diagnosis of specific diseases, to screen new candidates of a drug, to monitor therapeutic effects in real time, and to communicate with both diagnosis and therapeutics. These diverse advantages of molecular imaging can be allowed by development of nanoplatform technology. The nanoplatform-based probes for molecular imaging is widely investigated to grant multimodal molecular imaging and drug delivery together with medical imagings, which includes the issues of biocompatibility, targeting moiety, proteasespecific peptide substrate, quenching/dequenching system etc. In this paper, nanoplatformbased probes are reviewed in aspects of cancer targeting for diagnosis and therapy and multimodal molecular imaging with inorganic/organic hybrid nanoparticles.

Multifunctional Nanoparticles for Molecular Imaging

Molecular imaging is a bioimaging that can detect biochemically and genetically relevant events in molecular level in cells and tissues via quantitative imaging signal. Molecular imaging provides potential advantages to examine early diagnosis of specific diseases, to screen new candidates of a drug, to monitor therapeutic effects in real time, and to communicate with both diagnosis and therapeutics. These diverse advantages of molecular imaging can be allowed by development of nanoplatform technology. The nanoplatform-based probes for molecular imaging is widely investigated to grant multimodal molecular imaging and drug delivery together with medical imagings, which includes the issues of biocompatibility, targeting moiety, proteasespecific peptide substrate, quenching/dequenching system etc. In this paper, nanoplatformbased probes are reviewed in aspects of cancer targeting for diagnosis and therapy and multimodal molecular imaging with inorganic/organic hybrid nanoparticles.

Effect of Calcium Sulfate-Chitosan Composite Pellet on Bone Formation in Bone Defect of Rabbits

This study was carried out on 80 New Zealand white rabbits, each weighing 3-3.5kg. Twenty rabbits were allocated into each of the four groups. After a 1cm sized ostectomy was made on the tibial body with the periosteum preserved, artificial bone substitutes were implanted. Except for control group(I), manufactured chitosan pellets were implanted in group II, Osteoset(R)(calcium sulfate) in group III and manufactured calcium sulfate-chitosan composite pellets in group IV. Results were evaluated using radiographic study, bone mineral density test and histologic examination in 2, 4, 6 weeks and three point bending test in 6 weeks after implantation. In the radiographic study, the formation and corticalization of callus were similar in groups III, IV and this was much earlier than in groups I, II. In the bone mineral density test and three point bending test to contralateral normal tibia in 6 weeks, the values in groups III and IV were statistically significantly higher than in groups I and II(p<0.05). In histologic examination, groups III and IV have more abundant and faster new bone formation than groups I and II. In conclusion, the synergistic effect between calcium sulfate and chitosan in group IV is considered to facilitate new bone formation as effectively as Osteoset(R) does.

Gene Therapy and Molecular Imaging

No abstract available.

Effect of Injectable Chitosan Bead Encapsulating Calcium Sulfate on Bony Consolidation in Distraction Osteogenesis

The purpose of this project was to study the effect of injectable chitosan bead encapsulating calcium sulfate, which makes sustained release of chitosan and calcium sulfate after implantation, on early bony consolidation in distraction osteogenesis of a dog model. Forty five dogs were used for this study. An external distraction device was applied to the mandibular body after vertical osteotomy and the mandibular distraction was started five days after the operation at a rate of 1mm per day up to a 10mm distraction. The experimental group was divided into a control group(I), hyaluronic acid group(II), chitosan group(III), calcium sulfate group(IV), and injectable chitosan bead encapsulating calcium sulfate group(V). Normal saline was injected in the group I. In the group II, a 1-ml volume of hyaluronic acid solution was injected into the distracted area. In the group III, a 1-ml of injectable solution of chitosan mixed with hyaluronic acid was implanted. In the group IV, a 1-ml of injectable solution of calcium sulfate mixed with hyaluronic acid was implanted. In the group V, injectable form of powders of chitosan bead encapsulating calcium sulfate mixed with a 1-ml volume of hyaluronic acid was implanted. Bone mineral density was measured in each group at third and sixth week. The mean three point failure load was measured in each group. In histological findings, new bone was generated in all groups. In the group IV and V, the formation of active woven bone was observed throughout the distracted area at sixth week. The amount of new bone formation in the distracted zone was in the order of the group IV and V, group III and group II, and control group. In conclusion, these findings suggest that injectable chitosan bead encapsulating calcium sulfate appears to be effective in early bony consolidation in distraction osteogenesis.

Effect of Growth Hormone on Early Bony Regeneration in Distraction Osteogenesis

The purpose of this project was to study the effect of growth hormone on early bony consolidation in distraction osteogenesis of a dog mandible. Sixteen dogs were used for this study. An external distraction device was applied to the mandibular body and the mandibular distraction was started five days after the operation at a rate of 1 mm per day up to a 10-mm distraction. Dogs in the growth hormone group received a daily subcutaneous injection of 1 IU of recombinant human growth hormone per kilogram of body weight per week. Normal saline was injected in the control group. Bone mineral density was higher in the growth hormone group than the control group in the whole period. Bone mechanical strength was 300% higher in the growth hormone group than that in the control group. However, results were more suggestive than conclusive. Upon histological examination, the formation of a substantial amount of active woven bone was observed throughout the distracted zone in 6 weeks in the growth hormone group. In the control group, new bone was generated from the edge to the center of the distracted zone. But, the most central area of the distracted zone was filled with fibrous tissue in 6 weeks. In conclusion, growth hormone appears to be effective in early bony consolidation in distraction osteogenesis.

The Effect of a Chitosan Coating of Dental Implant on the shock Absorption under Impact Test

With the object of providing a temporary artificial periodonal ligament-like membrane around the dental implant, 10 Branemark type implants were coated with commercially available chitosan(Fluka Co., Buchs, Switzerland) which has a molecular weight of 70,000 and 80% deacetylation degree. Once this bioactive hydrophillic polymer(chitosan) contacts with blood or wound fluids, it becomes swollen and penetrates into the adjacent cancellous bone. Thus the interface between implant and surrounding bone is completely filled with chitosan. This tight junction in early healing phase enhances primary stability. The chitosan coated dental implants were implanted into the fresh patella bones from porcine knees, since the thickness of cortical bone is relatively even and their cancellous structure is homogenous. To test the shock absorbing effect, 1mm delta-rogette strain gage was installed behind the implant. The results showed 1. the principal strain peak value directed to the impact of coated implant was 0.064 0.018(p<0.05) and that of uncoated implant was 0.095(0.032 p<0.05). 2. the peak time delay of coated implant was 0.056sec(0.011 p<0.05) and that of uncoated implant was 0.024sec(0.009 p<0.05). It can be reasoned from this results that the chitosan coating has a shock absorbing effect comparable with a temporary artificial periodontal ligament.

New Chronic Osteomyelitis Model in White Rabbit: A Preliminary Report / 대한정형외과연구학회지

The purpose of this study was to develope a rabbit model for the chronic osteomyelitis, which is reproducible, controllable in quantity of bacteria and suitable for toxicologic research and therapeutic intervention studies. Osteomyelitis was induced in white rabbits by injecting varying numbers of S. aureus(ATCC 19636, 49230) and Alginate-CaCl2 into the proximal metaphysis of tibia. Three rabbits were used in each number of S. aureus respectively. The tibia were harvested at 8 weeks later and evaluation was done by clinical, radiological and histological findings. Clinical sings of infection consisted of soft tissue swelling and limping in rabbits, Radiologic findings were periosteal reaction, osteolysis, new bone formation in proximal tibias. Histology showed chronic active inflammation, debris of alginate, clusters of bacterial and granulation tissue. In ATCC 19636(more than 6X105) inoculated rabbits, osteomyelitis was established consistently in all three rabbits. Using Alginate-CaCl2 and ATCC 19636 Staphylococcus aureus, we made a new chronic osteomyelitis model, reproducible and controllable in quantity of bacteria.