Hakan Orbay

University of California, Davis, Davis, California, United States

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Publications (97)

  • Source
    Yanhao Yu · Haiyan Sun · Hakan Orbay · [...] · Xudong Wang
    Full-text Article · Jul 2016 · Nano Energy
  • Source
    [Show abstract] [Hide abstract] ABSTRACT: As peripheral arterial disease (PAD) results in muscle ischemia and neovascularization, it has been claimed that nanoparticles can passively accumulate in ischemic tissues through the enhanced permeability and retention (EPR) effect. At this time, a quantitative evaluation of the passive targeting capabilities of nanoparticles has not been reported in PAD. Using a murine model of hindlimb ischemia, we quantitatively assessed the passive targeting capabilities of 64Cu-labeled PEGylated reduced graphene oxide – iron oxide nanoparticles (64Cu-RGO-IONP-PEG) through the EPR effect using positron emission tomography (PET) imaging. Serial laser Doppler imaging was performed to monitor changes in blood perfusion upon surgical induction of ischemia. Nanoparticle accumulation was assessed at 3, 10, and 17 days post-surgery and found to be highest at 3 days post-surgery, with the ischemic hindlimb displaying an accumulation of 14.7 ± 0.5 percent injected dose per gram (%ID/g). Accumulation of 64Cu-RGO-IONP-PEG was lowest at 17 days post-surgery, with the ischemic hindlimb displaying only 5.1 ± 0.5 %ID/g. Furthermore, nanoparticle accumulation was confirmed by photoacoustic imaging (PA). The combination of PET and serial Doppler imaging showed that nanoparticle accumulation in the ischemic hindlimb negatively correlated with blood perfusion. Thus, we quantitatively confirmed that 64Cu-RGO-IONP-PEG passively accumulated in ischemic tissue via the EPR effect, which is reduced as the perfusion normalizes. As 64Cu-RGO-IONP-PEG displayed substantial accumulation in the ischemic tissue, this nanoparticle platform may function as a future theranostic agent, providing both imaging and therapeutic applications.
    Full-text Article · May 2016 · Biomaterials
  • Heath J Charvet · Hakan Orbay · Lindsey Harrison · [...] · David E Sahar
    [Show abstract] [Hide abstract] ABSTRACT: Introduction: Fat grafting for breast cancer (BrCa) reconstruction and breast augmentation has become increasingly more popular. A major area of debate and controversy is the effect of adipose-derived stem cells (ASCs) on remnant or undetected BrCa cells. We investigate the in vitro response of BrCa to ASCs in a coculture model with regards to cell migration. Methods: The study was approved by the institutional review board. BrCa and adipose tissue specimens either from subcutaneous breast tissue or abdominal lipoaspirate were obtained from the same patient. BrCa cells and ASCs were harvested with either explant culture and/or enzymatic digestion. Tissues were grown in cell culture flasks until adequate cell libraries were established. Adipose-derived stem cells from adipose specimens were characterized with flow cytometry. Immunofluorescence (IF) staining of the initial cell population harvested from the BrCa specimens confirmed the presence of CD24, an epithelial marker of BrCa. A homogenous CD 24+/CD 90- BrCa cell population was obtained with flowcytometric cell sorting. The in vitro migration of BrCa cells was examined in coculture with and without ASCs. Results: Adipose-derived stem cells harvested from the adipose specimens were positive for mesenchymal stem cell markers CD 105, CD 90, CD 73, and CD 44 and negative for lymphocyte cell marker CD 34 and leukocyte marker CD 45. The percentage of the CD 24+/CD 90- BrCa cells in the initial cell population harvested from BrCa specimens was 0.61%. The BrCa cells morphologically had large nuclei and small cytoplasm in clusters under the light microscope, suggesting a cancer cell phenotype. CD 24 expression on the surface of BrCa cells was confirmed with IF staining. The number of BrCa cells migrated in ASCs coculture was approximately 10 times higher than the number of BrCa cells migrated in BrCa cell only cultures. Conclusions: Adipose-derived stem cells significantly increase the migration capacity of BrCa cells in vitro in cocultures. This should be taken into consideration when performing fat grafting to the breast especially in patients with a history of BrCa or strong family history of BrCa.
    Article · Apr 2016 · Annals of plastic surgery
  • Source
    Fonny Josh · hakan Orbay · Hiroshi Mizuno
    [Show description] [Hide description] DESCRIPTION: Indonesian Journal of Surgery, 2012, volume 39-40 no 1-2 December 2012
    Full-text Research · Apr 2016
  • [Show abstract] [Hide abstract] ABSTRACT: The engineering of a novel dual-modality imaging probe is reported here by intrinsically labeling zirconium-89 ((89) Zr, a positron emission radioisotope with a half-life of 78.4 h) to PEGylated Gd2 O2 S:Eu nanophorphors, forming [(89) Zr]Gd2 O2 S:Eu@PEG for in vivo positron emission tomography/radioluminescence lymph node mapping.
    Article · Apr 2016 · Small
  • Samuel Lance · Lindsey Harrison · Hakan Orbay · [...] · David Sahar
    [Show abstract] [Hide abstract] ABSTRACT: The use of negative-pressure wound therapy (NPWT) for management of open wounds and immobilization of split-thickness skin grafts (STSGs) over wounds has been well described. However, there is a concern for potential compromise of flap viability when NPWT is used for skin grafts over pedicled muscle flaps. We have used NPWT to immobilize STSGs in eight patients who underwent a pedicled gastrocnemius muscle flap operation in our department. We applied a negative pressure of −75 mmHg on the muscle flaps for 5 days postoperatively. All wounds healed successfully, with a 97.5 ± 5.5% mean STSG uptake. No flap necrosis was observed. In our series, the use of NPWT for fixation of STSGs over pedicled gastrocnemius muscle flap was effective and had no negative impact on flap viability.
    Article · Nov 2015 · Journal of Plastic Reconstructive & Aesthetic Surgery
  • Chenyu Huang · Hakan Orbay · Morikuni Tobita · [...] · Hiroshi Mizuno
    [Show abstract] [Hide abstract] ABSTRACT: The ability of basic fibroblast growth factor (bFGF) to improve wound healing is attenuated by its short half-life in free form. This study aimed to enhance skin wound healing in a diabetes mouse model while concomitantly decreasing scar formation by using control-released bFGF together with acidic gelatin hydrogel microspheres (AGHMs). Bilateral full-thickness wounds (10 mm in diameter) were made on the backs of db/db mice. Forty-five mice were divided into three groups, and the base of the wound under the panniculus carnosus and the wound periphery were injected with phosphate-buffered saline (PBS) (300 µl) containing (1) control-released bFGF (50 μg), (2) control-released bFGF (20 μg), or (3) AGHMs alone. The size of the wound area was recorded on each postoperative day (POD). Mice were sacrificed on POD 4, 7, 10, 14, and 28, and skin wound specimens were obtained to assess the endothelium/angiogenesis index via cluster of differentiation (CD) 31 immunohistochemistry (IHC), the proliferation index via Ki-67 IHC, and the myofibroblast and fibroblast apoptosis indices by terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL) and alpha-smooth muscle actin (α-SMA) or vimentin staining, respectively. Epithelization rates and indices of proliferation and myofibroblast/fibroblast apoptosis were higher in the bFGF groups than in the AGHM group, mainly within 2 weeks of injury. No dose-effect relationship was found for control-released bFGF, although the actions of 50 μg bFGF seemed to last longer than those of 20 μg bFGF. Therefore, control-released bFGF may accelerate diabetic skin wound healing and induce myofibroblast/fibroblast apoptosis, thereby reducing scar formation. This article is protected by copyright. All rights reserved.
    Article · Oct 2015 · Wound Repair and Regeneration
  • [Show abstract] [Hide abstract] ABSTRACT: Fat grafting is increasingly popular and is becoming a common practice in plastic surgery for postmastectomy breast reconstruction and aesthetic breast augmentation; however, concerns over the oncologic safety remains a controversial and hot topic among scientists and surgeons. Basic science and laboratory research repeatedly show a potentially dangerous effect of adipose-derived stem cells on breast cancer cells; however, clinical research, although limited, continually fails to show an increase in breast cancer recurrence after breast fat grafting, with the exception of 1 small study on a subset patient population with intraepithelial neoplasm of the breast. The aim of this review is to summarize the recent conflicting basic science and clinical data to better understand the safety of breast fat grafting from an oncological perspective.
    Article · Sep 2015 · Annals of plastic surgery
  • Hakan Orbay · Brittany K Busse · Thomas R Stevenson · [...] · David E Sahar
    [Show abstract] [Hide abstract] ABSTRACT: Deep inferior epigastric artery perforator (DIEP) flap breast reconstruction requires complex microsurgical skills. Herein, we examine whether DIEP flap breast reconstruction can be performed safely without microsurgical fellowship training. A total of 28 patients and 34 DIEP flaps were included in the study. We reviewed the medical records of patients for donor site and flap-related complications and analyzed the correlation between the complications and preoperative risk factors. We also performed a literature review to compare complication rates in our series with the literature. We observed total flap necrosis in 1 patient (2.9%), partial flap necrosis in 5 patients (14.7%), infection in 1 patient (2.9%), hematoma/seroma in 3 patients (8.8%), donor site complications in 5 patients (18.5%), venous occlusion in 4 patients (11.7%), and arterial occlusion in 1 patient (2.9%). We did not observe any correlation between complications and preoperative risk factors. Literature review yielded 18 papers that met our inclusion criteria. Partial flap necrosis rate was significantly higher in our series compared with literature (14.7% vs 1.6%, P = 0.003). Venous complication rate was marginally higher in our series compared with literature (11.7% vs 3.3%, P = 0.057). However, total flap loss rate in our series was comparable with the literature (2.9% vs 2.2%, P = 0.759). With proper training during plastic surgery residency, DIEP flap can be performed with acceptable morbidity.
    Article · Jul 2015
  • [Show abstract] [Hide abstract] ABSTRACT: 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.
    Article · Jun 2015 · Expert opinion on biological therapy
  • Hakan Orbay · Lindsey Harrison · Kamaljit Devi · [...] · David E Sahar
    Article · May 2015 · Plastic and Reconstructive Surgery
  • Dataset · Apr 2015
  • Source
    Sixiang Shi · Hakan Orbay · Yunan Yang · [...] · Weibo Cai
    [Show abstract] [Hide abstract] ABSTRACT: The critical challenge in abdominal aortic aneurysm (AAA) research is the accurate diagnosis and assessment of AAA progression. Angiogenesis is a pathological hallmark of AAA, and CD105 is highly expressed on newly formed vessels. Our goal was to use (64)Cu-labeled anti-CD105 antibody Fab fragment for noninvasive assessment of angiogenesis in the aortic wall in a murine model of AAA. Fab fragment of TRC105, a mAb that specifically binds to CD105, was generated by enzymatic papain digestion and conjugated to NOTA for (64)Cu-labeling. 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, which underwent weekly PET scans using (64)Cu-NOTA-TRC105-Fab. Biodistribution and autoradiography studies were also performed to confirm the accuracy of PET results. NOTA-TRC105-Fab exhibited high purity and specifically bound to CD105 in vitro. Uptake of (64)Cu-NOTA-TRC105-Fab increased from a control level of 3.4 ± 0.1 to 9.5 ± 0.4 %ID/g at 6 h p.i. 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. (64)Cu-NOTA-TRC105-Fab cleared rapidly through kidneys, which enabled noninvasive PET imaging of the aorta with enhanced contrast and showed increased angiogenesis (CD105 expression) during AAA. (64)Cu-NOTA-TRC105-Fab PET may potentially be used for future diagnosis and prognosis of AAA. Copyright © 2015 by the Society of Nuclear Medicine and Molecular Imaging, Inc.
    Full-text Article · Apr 2015 · Journal of Nuclear Medicine
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    [Show abstract] [Hide abstract] ABSTRACT: Actively targeted theranostic nanomedicine may be the key for future personalized cancer management. Although numerous types of theranostic nanoparticles have been developed in the last 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 multi-step surface engineering to form the final theranostic nanoparticle. Systematic in vitro targeting, an in vivo long-term toxicity study, photothermal ablation evaluation, in vivo vasculature targeted imaging, and biodistribution and histology studies were performed to fully explore the potential of these as-developed new theranostic nanoparticles.
    Full-text Article · Apr 2015 · ACS Nano
  • Sixiang Shi · Hao Hong · Hakan Orbay · [...] · Weibo Cai
    [Show abstract] [Hide abstract] ABSTRACT: To date, there is no effective therapy for triple-negative breast cancer (TNBC), which has a dismal clinical outcome. Upregulation of tissue factor (TF) expression leads to increased patient morbidity and mortality in many solid tumor types, including TNBC. Our goal was to employ the Fab fragment of ALT-836, a chimeric anti-human TF mAb, for PET imaging of TNBC, which can be used to guide future TNBC therapy. ALT-836-Fab was generated by enzymatic papain digestion. SDS-PAGE and FACS studies were performed to evaluate the integrity and TF binding affinity of ALT-836-Fab before NOTA conjugation and (64)Cu-labeling. Serial PET imaging and biodistribution studies were carried out to evaluate the tumor targeting efficacy and pharmacokinetics in the MDA-MB-231 TNBC model, which expresses high levels of TF on the tumor cells. Blocking studies, histological assessment, as well as RT-PCR were performed to confirm TF specificity of (64)Cu-NOTA-ALT-836-Fab. ALT-836-Fab was produced with high purity, which exhibited superb TF binding affinity and specificity. Serial PET imaging revealed rapid and persistent tumor uptake of (64)Cu-NOTA-ALT-836-Fab (5.1 ± 0.5 %ID/g at 24 h post-injection; n = 4) and high tumor/muscle ratio (7.0 ± 1.2 at 24 h post-injection; n = 4), several-fold higher than that of the blocking group and tumor models that do not express significant level of TF, which was confirmed by biodistribution studies. TF specificity of the tracer was also validated by histology and RT-PCR. (64)Cu-NOTA-ALT-836-Fab exhibited prominent tissue factor targeting efficiency in MDA-MB-231 TNBC model. The use of a Fab fragment led to fast tumor uptake and good tissue/muscle ratio, which may be translated into same-day immunoPET imaging in the clinical setting to improve TNBC patient management.
    Article · Mar 2015 · European Journal of Nuclear Medicine
  • [Show abstract] [Hide abstract] ABSTRACT: Radical oncologic resection can result in large soft tissue defects with exposure of underlying vessels. Unless immediately covered with viable soft tissue, these vessels are vulnerable to desiccation from air exposure and mechanical trauma. Local radiation treatment also contributes to a decline in vessel wall strength. We present an index case of a patient with prolonged exposure of her femoral bone and superficial femoral artery after an initial failed reconstruction of a soft tissue sarcoma resection defect. We provided coverage using a free latissimus dorsi muscle flap. Two weeks after the initial free flap operation, the patient was readmitted to emergency service with profuse bleeding from beneath the free flap. Intraoperative inspection revealed a 2-cm defect of the irradiated superficial femoral artery. The defect was repaired with cryopreserved human arterial graft, and the flap was reset. This case highlights the importance of immediate coverage of soft tissue defects after oncologic resection. If any vessels are left exposed, they should be closely inspected before a delayed flap coverage to rule out future sources of bleeding that may jeopardize the outcomes of an otherwise successful free flap operation.
    Article · Mar 2015 · Annals of Plastic Surgery
  • Hakan Orbay · Christopher J Little · Lee Lankford · [...] · David E Sahar
    [Show abstract] [Hide abstract] ABSTRACT: Schwann cell-like cells differentiated from adipose-derived stem cells may have an important role in peripheral nerve regeneration. Herein, we document the individual effects of growth factors in Schwann cell-like differentiation medium. There were 6 groups in the study. In the control group, we supplemented the rat adipose-derived stem cells with normal cell culture medium. In group 1, we fed the cells with Schwann cell-like differentiation medium (normal cell culture medium supplemented with platelet-derived growth factor, basic fibroblast growth factor, forskolin, and glial growth factor). In the other groups, we removed the components of the medium one at a time from the differentiation medium so that group 2 lacked glial growth factor, group 3 lacked forskolin, group 4 lacked basic fibroblast growth factor, and group 5 lacked platelet-derived growth factor. We examined the expression of the Schwann cell-specific genes with quantitative reverse transcription polymerase chain reaction and immunofluorescence staining in each group. Groups 3 and 4, lacking forskolin and basic fibroblast growth factor, respectively, had the highest expression levels of integrin-β4, and p75. Group 1 showed a 3.2-fold increase in the expression of S100, but the expressions of integrin-β4 and p75 were significantly lower compared to groups 3 and 4. Group 2 [glial growth factor (-)] did not express significant levels of Schwann cell-specific genes. The gene expression profile in group 4 most closely resembled Schwann cells. Immunofluorescence staining results were parallel with the quantitative real-time polymerase chain reaction results. Glial growth factor is a key component of Schwann cell-like differentiation medium.
    Article · Jan 2015 · Annals of Plastic Surgery
  • Article · Jan 2015 · Plastic & Reconstructive Surgery
  • Source
    Brittany Busse · Hakan Orbay · David E Sahar
    [Show abstract] [Hide abstract] ABSTRACT: Prosthetic implants are frequently used for breast augmentation and breast reconstruction following mastectomy. Unfortunately, long-term aesthetic results of prosthetic breast restoration may be hindered by complications such as rippling, capsular contracture, and implant malposition. The advent of use of acellular dermal matrices has greatly improved the outcomes of prosthetic breast reconstruction. We describe a case of rippling deformity of breast that was treated using an acellular dermal matrix product, AlloMax. The patient presented with visible rippling of bilateral prosthetic breast implants as well as significant asymmetry of the breasts after multiple excisional biopsies for right breast ductal carcinoma in situ. A 6 × 10 cm piece of AlloMax was placed on the medial aspect of each breast between the implant and the skin flap. Follow-up was performed at 1 week, 3 months, and 1 year following the procedure. The patient recovered well from the surgery and there were no complications. At her first postoperative follow-up the patient was extremely satisfied with the result. At her 3-month and 1-year follow-up she had no recurrence of her previous deformity and no new deformity.
    Full-text Article · Dec 2014
  • Satoshi Tajima · Morikuni Tobita · Hakan Orbay · [...] · Hiroshi Mizuno
    [Show abstract] [Hide abstract] ABSTRACT: 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. Micro-computed 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.
    Article · Oct 2014 · Tissue Engineering Part A

Publication Stats

555 Citations


  • 2015
    • University of California, Davis
      • Division of Plastic Surgery
      Davis, California, United States
    • Nippon Medical School
      Edo, Tokyo, Japan
    • University of Wisconsin–Madison
      Madison, Wisconsin, United States