Hakan Orbay

In Vivo Tumor Vasculature Targeting of CuS@MSN Based Theranostic Nanomedicine

Actively targeted theranostic nanomedicine may be the key for future personalized cancer management. Although numerous types of theranostic nanoparticles have been developed in the past decade for cancer treatment, challenges still exist in the engineering of biocompatible theranostic nanoparticles with highly specific in vivo tumor targeting capabilities. Here, we report the design, synthesis, surface engineering, and in vivo active vasculature targeting of a new category of theranostic nanoparticle for future cancer management. Water-soluble photothermally sensitive copper sulfide nanoparticles were encapsulated in biocompatible mesoporous silica shells, followed by multistep surface engineering to form the final theranostic nanoparticles. Systematic in vitro targeting, an in vivo long-term toxicity study, photothermal ablation evaluation, in vivo vasculature targeted imaging, biodistribution and histology studies were performed to fully explore the potential of as-developed new theranostic nanoparticles.

Differentiated and undifferentiated adipose-derived stem cells improve function in rats with peripheral nerve gaps

The effect of differentiated and undifferentiated adipose-derived stem cells on the repair of peripheral nerve gaps was studied. Adipose-derived stem cells were maintained in differentiation medium for 2 weeks. The expression of Schwann cell proteins S-100, nerve growth factor receptor (NGFR) p75 and integrin β4 was examined by immunofluorescence staining and real time-polymerase chain reaction (real time-PCR) at the end of the differentiation period. A 10-mm gap on the left sciatic nerves of 20 Fischer rats was created and bridged with silicone tube (group I), silicone tube filled with collagen gel (group II), nerve graft (group III), silicone tube filled with adipose-derived stem cells (group IV) and silicone tube filled with differentiated adipose-derived stem cells (group V). In vitro, the positivity of differentiated adipose-derived stem cells for S-100, NGFR p75 and integrin β4 by immunofluorescence staining was 31%, 27% and 12%, respectively. Fold changes by real time-PCR in comparison with undifferentiated cells were 48.4, 168.7 and 284.85, respectively. In vivo, a walking track analysis did not yield any statistically significant differences after 3 months postoperatively; however, after 6 months, group IV (sciatic function index (SFI) = -49.1 ± 13.1) and V (SFI = -52.6 ± 5.7) showed significant improvement compared to other groups (I: -73.3 ± 5.07, II: -79.6 ± 12.01, III: -74.8 ± 12.89) (p < 0.05). Nerve conduction velocity after 6 months was higher in groups IV (4.44 ± 0.3 mm ms(-1)), V (4.25 ± 0.3 mm ms(-1)) and III (4 ± 0.3 mm ms(-1)) than in groups I (2.5 ± 2.25 mm ms(-1)) and II (2.35 ± 1.58 mm ms(-1)) (p > 0.05). Myelin fibre density and myelinated fibre/unmyelinated fibre ratio were significantly higher in the midnerve and the distal nerve in groups IV and V (p < 0.05). These results reveal the therapeutic potential of adipose-derived stem cells in nerve reconstruction.

An Alternative Dressing Material for the Split-thickness Skin Graft Donor Site: Oxidized Regenerated Cellulose

The split-thickness skin graft (STSG) donor sites have been treated with various and plenty of dressing techniques and materials. An ideal STSG donor site dressing should have antibacterial, hemostatic, and promoting epidermal healing properties. We have performed a prospective study to evaluate the effect of the oxidized regenerated cellulose on STSG donor site healing. Between January 2002 and January 2005, 40 patients who were operated in any kind of reconstructive operations with STSG donor sites were included in the study. One half of the wound was covered with oxidized regenerated cellulose and the other half of the same wound of the same patient was covered with fine mesh gauze treated with Furacin (nitrofurazone). The patients were grouped into 2 depending on the dressing technique: group I, semiclosed and group II, closed. The wounds were evaluated for healing time, infection, pain perception of the patient, and final esthetic results. The oxidized regenerated cellulose side of the group I was healed in a mean of 6.5 ± 0.51 days; in group II, 5.4 ± 0.50 days (range, 5–6 days). The fine mesh gauze treated with Furacin in group I was healed in a mean of 9.9 ± 0.97 days (range, 8–11 days); in group II, 8.4 ± 0.99 days (range, 7–10 days). There was a statistical significance between the oxidized regenerated cellulose side and the fine mesh gauze side (P < 0.001) in group I and group II separately. The difference between group I and group II was statistically significant in the oxidized regenerated cellulose side (P < 0.001), and the difference between group I and group II was statistically significant in the fine mesh gauze side (P < 0.005). The antibacterial, hemostatic, and absorbable property of the oxidized regenerated cellulose could ensure the utilization as an alternative STSG donor site dressing, especially because the positive influence over the wound healing was proven.

Adipose-derived stem cells for wound repair and regeneration

Introduction: The use of undifferentiated cells for cell-based tissue repair and regeneration strategies represents a promising approach for chronic wound healing. Multipotent adult stem cells isolated from adipose tissue, termed adipose-derived stem cells (ASCs), appear to be an ideal population of stem cells because they are autologous, non-immunogenic, plentiful, and easily obtained. Both preclinical and clinical studies have revealed that ASCs have potential for wound healing due to the mechanisms described below. Areas covered: Both in vitro and in vivo studies demonstrated that ASCs not only differentiate into keratinocytes, fibroblasts, and endothelial cells, as evidenced by their morphology, expression of cell surface markers, and gene expression, but also secrete several soluble factors, which positively contribute to wound healing in a paracrine manner. Clinical trials have been conducted using autologous ASCs with great success. Expert opinion: There remain many concerns regarding the use of ASCs, including how these cells act as precursors of keratinocytes, fibroblasts, and endothelial cells, or as a secretion vehicle of soluble factors. Further studies are necessary to establish the optimal strategy for the treatment of chronic wounds in patients with different disease backgrounds.

PET/SPECT imaging of hindlimb ischemia: focusing on angiogenesis and blood flow

Peripheral artery disease (PAD) is a result of the atherosclerotic narrowing of blood vessels to the extremities, and the subsequent tissue ischemia can lead to the up-regulation of angiogenic growth factors and formation of new vessels as a recovery mechanism. Such formation of new vessels can be evaluated with various non-invasive molecular imaging techniques, where serial images from the same subjects can be obtained to allow the documentation of disease progression and therapeutic response. The most commonly used animal model for preclinical studies of PAD is the murine hindlimb ischemia model, and a number of radiotracers have been investigated for positron emission tomography (PET) and single photon emission computed tomography (SPECT) imaging of PAD. In this review article, we summarize the PET/SPECT tracers that have been tested in the murine hindlimb ischemia model as well as those used clinically to assess the extremity blood flow.

Positron emission tomography imaging of atherosclerosis.

Atherosclerosis-related cardiovascular events are the leading causes of death in the industrialized world. Atherosclerosis develops insidiously and the initial manifestation is usually sudden cardiac death, stroke, or myocardial infarction. Molecular imaging is a valuable tool to identify the disease at an early stage before fatal manifestations occur. Among the various molecular imaging techniques, this review mainly focuses on positron emission tomography (PET) imaging of atherosclerosis. The targets and pathways that have been investigated to date for PET imaging of atherosclerosis include: glycolysis, cell membrane metabolism (phosphatidylcholine synthesis), integrin αvβ3, low density lipoprotein (LDL) receptors (LDLr), natriuretic peptide clearance receptors (NPCRs), fatty acid synthesis, vascular cell adhesion molecule-1 (VCAM-1), macrophages, platelets, etc. Many PET tracers have been investigated clinically for imaging of atherosclerosis. Early diagnosis of atherosclerotic lesions by PET imaging can help to prevent the premature death caused by atherosclerosis, and smooth translation of promising PET tracers into the clinic is critical to the benefit of patients.

Biocompatibility and in vivo operation of implantable mesoporous PVDF-based nanogenerators

The rapid developments of implantable biomedical electronics give rise to the motivation of exploring efficient and durable self-powered charging system. In this paper, we report a mesoporous polyvinylidene fluoride (PVDF)-based implantable piezoelectric nanogenerator (NG) for in vivo biomechanical energy harvesting. The NG was built with a sponge-like mesoporous PVDF film and encapsulated by polydimethylsiloxane (PDMS). After embedding this NG into rodents, a Voc of ~200 mV was produced from the gentle movement of rodent muscle. Meanwhile, no toxicity or incompatibility sign was found in the host after carrying the packaged NG for 6 weeks. Moreover, the electric output of this NG was extremely stable and exhibited no deterioration after 5 days of in vivo operation or 1.512 × 108 times mechanical deformation. This NG device could practically output a constant voltage of 52 mV via a 1 µF capacitor under living circumstance. The outstanding efficiency, magnificent durability and exceptional biocompatibility promise this mesoporous PVDF-based NG in accomplishing self-powered bioelectronics with potentially lifespan operation period.

Direct and indirect effects of a combination of adipose-derived stem cells and platelet-rich plasma on bone regeneration.

A key goal for successful bone regeneration is to bridge a bone defect using healing procedures that are stable and durable. Adipose-derived stem cells (ASCs) have the potential to differentiate into bone. Meanwhile, platelet-rich plasma (PRP) is an interesting biological means to repair tissue by inducing chemotactic, proliferative, and anabolic cellular responses. This study evaluated bone regeneration using a combination of ASCs and PRP in a rat calvarial defect model. ASCs were isolated from inguinal fat pads of F344 inbred rats, while PRP was prepared from these rats. ASCs were cultured in control medium supplemented with 10% fetal bovine serum or 5% PRP in vitro. After 1 week, levels of growth factors including insulin-like growth factor-1, transforming growth factor-β1, hepatocyte growth factor, and vascular endothelial growth factor in the culture supernatant were measured by enzyme-linked immunosorbent assays. Moreover, the ASC/PRP admixture was transplanted into the rat calvarial defect. Microcomputed tomography, histological, and immunohistochemical (osteopontin and osteocalcin) analyses were performed at 4 and 8 weeks after transplantation. The in vitro study showed that the levels of growth factors secreted by ASCs were significantly increased by the addition of PRP. Transplantation of the ASC/PRP admixture had dramatic effects on bone regeneration overtime in comparison with rats that received other transplants. Furthermore, some ASCs directly differentiated into osteogenic cells in vivo. These findings suggest that the combination of ASCs and PRP has augmentative effects on bone regeneration. The ASC/PRP admixture may be a promising source for the clinical treatment of cranial defects.

Molecular Imaging Strategies for In Vivo Tracking of MicroRNAs: a Comprehensive Review

MicroRNAs (miRNAs) are single-stranded non-coding RNAs of ~22 nucleotides, which can negatively regulate gene expression through induction of mRNA degradation and/or post-transcriptional gene silencing. MiRNAs are key factors in the regulation of many biological processes such as cell proliferation, differentiation, and death. Since miRNAs are known to be in close association with cancer development, non-invasive imaging of miRNA expression and/or activity is of critical importance, for which conventional molecular biology techniques are not suitable or applicable. Over the last several years, various molecular imaging techniques have been investigated for imaging of miRNAs. In this review article, we summarize the current state-of-the-art imaging of miRNAs, which are typically based on fluorescent proteins, bioluminescent enzymes, molecular beacons, and/or various nanoparticles. Non-invasive imaging of miRNA expression and/or biological activity is still at its infancy. Future research on more clinically relevant, non-toxic techniques is required to move the field of miRNA imaging into clinical applications. Non-invasive imaging of miRNA is an invaluable method that can not only significantly advance our understandings of a wide range of human diseases, but also lead to new and more effective treatment strategies for these diseases.

PET Imaging of Abdominal Aortic Aneurysm with 64Cu-Labeled Anti-CD105 Antibody Fab Fragment

The critical challenge in abdominal aortic aneurysm (AAA) research is the accurate diagnosis and assessment of AAA progression. Angiogenesis is a pathologic hallmark of AAA, and CD105 is highly expressed on newly formed vessels. Our goal was to use 64Cu-labeled anti-CD105 antibody Fab fragment for noninvasive assessment of angiogenesis in the aortic wall in a murine model of AAA. Methods: Fab fragment of TRC105, a mAb that specifically binds to CD105, was generated by enzymatic papain digestion and conjugated to NOTA (1,4,7-triazacyclononane-1,4,7-triacetic acid) for 64Cu labeling. The binding affinity/specificity of NOTA-TRC105-Fab was evaluated by flow cytometry and various ex vivo studies. BALB/c mice were anesthetized and treated with calcium phosphate to induce AAA and underwent weekly PET scans using 64Cu-NOTA-TRC105-Fab. Biodistribution and autoradiography studies were also performed to confirm the accuracy of PET results. Results: NOTA-TRC105-Fab exhibited high purity and specifically bound to CD105 in vitro. Uptake of 64Cu-NOTA-TRC105-Fab increased from a control level of 3.4 ± 0.1 to 9.5 ± 0.4 percentage injected dose per gram (%ID/g) at 6 h after injection on day 5 and decreased to 7.2 ± 1.4 %ID/g on day 12, which correlated well with biodistribution and autoradiography studies (i.e., much higher tracer uptake in AAA than normal aorta). Of note, enhanced AAA contrast was achieved, due to the minimal background in the abdominal area of mice. Degradation of elastic fibers and highly expressed CD105 were observed in ex vivo studies. Conclusion: 64Cu-NOTA-TRC105-Fab cleared rapidly through the kidneys, which enabled noninvasive PET imaging of the aorta with enhanced contrast and showed increased angiogenesis (CD105 expression) during AAA. 64Cu-NOTA-TRC105-Fab PET may potentially be used for future diagnosis and prognosis of AAA.