Ofra Ziv-Polat

Dr Ofra Ziv-Polat

PhD

NVR (Neuronal and Vascular Reconstruction) Research Ltd

Senior Scientist

Israel

Specialties: Chemist and Biologist, specialties in synthesis and characterization of nanoparticles for medical applications, development of tissue engineered implants for the CNS and PNS, and immunology

Ofra Ziv-Polat

Dr Ofra Ziv-Polat

PhD
Metrics

17

Publications

192

Profile Views

23

Reads

47

PubMed Central Citations

Top co-authors

Publications

17Publications

23Reads

47PubMed Central Citations

Peripheral Nerve Regeneration Through Hydrogel-Enriched Chitosan Conduits Containing Engineered Schwann Cells for Drug Delivery.

Cell Transplant 2016 14;25(1):159-82. Epub 2015 Apr 14.

Institute of Neuroanatomy, Hannover Medical School, Hannover, Lower-Saxony, Germany.

View Article
October 2016
5 Reads
1 PubMed Central Citation(source)
3.57 Impact Factor

Induction of neurite outgrowth in 3D hydrogel-based environments.

Biomed Mater 2015 Oct 20;10(5):051001. Epub 2015 Oct 20.

Life and Health Sciences Research Institute (ICVS), School of Health Sciences, University of Minho, Campus de Gualtar, 4701-057 Braga, Portugal. ICVS/3B's-PT Government Associate Laboratory, Braga/Guimarães, Portugal. R C Assunção-Silva and C C Oliveira contributed equally to this work.

View Article
October 2015
2 Reads
3.70 Impact Factor

The role of neurotrophic factors conjugated to iron oxide nanoparticles in peripheral nerve regeneration: in vitro studies.

Biomed Res Int 2014 16;2014:267808. Epub 2014 Jul 16.

Institute of Nanotechnology and Advanced Materials, Department of Chemistry, Bar-Ilan University, 52900 Ramat-Gan, Israel.

View Article
September 2015
1 Read
6 PubMed Central Citations(source)

Nanotechnology versus stem cell engineering: in vitro comparison of neurite inductive potentials.

Int J Nanomedicine 2014 14;9:5289-306. Epub 2014 Nov 14.

Institute of Neuroanatomy, Hannover Medical School, Hannover, Lower-Saxony, Germany ; Center for Systems Neuroscience (ZSN), Hannover, Lower-Saxony, Germany.

View Article
July 2015
1 Read
2 PubMed Central Citations(source)

Bioactive magnetic near Infra-Red fluorescent core-shell iron oxide/human serum albumin nanoparticles for controlled release of growth factors for augmentation of human mesenchymal stem cell growth and differentiation.

J Nanobiotechnology 2015 May 7;13:34. Epub 2015 May 7.

Goldschleger Eye Institute, Sackler Faculty of Medicine, Tel Aviv University, Sheba Medical Center, Tel-Hashomer, 52621, Israel.

View Article
May 2015
5 Reads
2 PubMed Central Citations(source)
4.08 Impact Factor

Application of iron oxide anoparticles in neuronal tissue engineering.

Neural Regen Res 2015 Feb;10(2):189-91

N.V.R Research Ltd., 11 Heharash St, Ness-Ziona 74031, Israel.

View Article
February 2015
1 Read
0.23 Impact Factor

The Role of Neurotrophic Factors Conjugated to Iron Oxide Nanoparticles in Peripheral Nerve Regeneration: In Vitro Studies

BioMed Research International, vol. 2014, Article ID 267808, 10 pages, 2014. doi:10.1155/2014/267808

BioMed Research International

Local delivery of neurotrophic factors is a pillar of neural repair strategies in the peripheral nervous system. The main disadvantage of the free growth factors is their short half-life of few minutes. In order to prolong their activity, we have conjugated to iron oxide nanoparticles three neurotrophic factors: nerve growth factor (βNGF), glial cell-derived neurotrophic factor (GDNF) and basic fibroblast growth factor (FGF-2). Comparative stability studies of free versus conjugated factors revealed that the conjugated neurotrophic factors were significantly more stable in tissue cultures and in medium at 37 °C. The biological effects of free versus conjugated neurotrophic factors were examined on organotypic dorsal root ganglion (DRG) cultures performed in NVR-Gel, composed mainly of hyaluronic acid and laminin. Results revealed that the conjugated neurotrophic factors enhanced early nerve fiber sprouting compared to the corresponding free factors. The most meaningful result was that conjugated-GDNF accelerated the onset and progression of myelin significantly earlier than the free GDNF and the other free and conjugated factors. This is probably due to the beneficial and long-acting effect that the stabilized conjugated-GDNF had on neurons and Schwann cells. These conclusive results make NVR-Gel enriched with conjugated-GDNF a desirable scaffold for the reconstruction of severed peripheral nerve.

View Article
July 2014
11 Reads

Engineering of new crosslinked functional PEG micrometer-sized particles of narrow size distribution for enzyme immobilization

Polymer. 2013;54(12):2926-34

Polymer

New functional crosslinked poly(ethylene glycol) (PEG) micrometer-sized particles of narrow size distribution were prepared by dispersion co-polymerization in an aqueous continuous phase of the monomers methacrylate polyethylene glycol carboxylic acid (MA-PEG-COOH) or methacrylate polyethylene glycol amine (MA-PEG-NH2) with polyethylene glycol methacrylate ether (MA-PEG-OCH3) and the crosslinker monomer polyethylene glycol dimethacrylate (PEDMA). The effect of various polymerization parameters, e.g., total monomer concentration, crosslinker monomer concentration, initiator concentration and stabilizer concentration and Mw on the size, size distribution and polymerization yield of the produced particles has been studied. As a model for enzyme immobilization, trypsin was covalently bound to the functional PEG particles. A substantial loss in the activity and an increase in the stability of the conjugated enzyme, as compared to the free one, were demonstrated.

View Article
April 2013
8 Reads

Novel magnetic fibrin hydrogel scaffolds containing thrombin and growth factors conjugated iron oxide nanoparticles for tissue engineering.

Int J Nanomedicine 2012 6;7:1259-74. Epub 2012 Mar 6.

Department of Chemistry, Bar-Ilan Institute of Nanotechnology and Advanced Materials, Ramat-Gan, Israel.

View Article
June 2012
8 PubMed Central Citations(source)

Magnetic scaffolds enriched with bioactive nanoparticles for tissue engineering.

Adv Healthc Mater 2012 Mar 13;1(2):168-71. Epub 2012 Feb 13.

Department of Chemistry, Bar-Ilan Institute of Nanotechnology and Advanced Materials, Ramat-Gan 52900, Israel.

View Article
March 2012
1 Read
3 PubMed Central Citations(source)
4.88 Impact Factor

Functionalised, photostable, fluorescent polystyrene nanoparticles of narrow size-distribution

Journal of Photochemistry and Photobiology A: Chemistry. 2012;228(1):1-68

Journal of Photochemistry and Photobiology A: Chemistry

Fluorescent nanoparticles continue to be of wide interest, as they have many advantages over single fluorescent molecules for biological imaging and sensing applications, such as increased fluorescence intensity and reduced photobleaching. In the following work, styrene was copolymerised with a newly synthesised, fluorescein-based, vinylic crosslinking monomer, by emulsion polymerisation, to create a series of different sized fluorescent nanoparticles (35–100 nm), each of narrow size-distribution. The particles were found to be highly fluorescent and with lower photobleaching compared to fluorescein isothiocyanate (FITC), offering an attractive alternative. The fluorescence excitation and emission spectra were recorded, being similar to fluorescein, but with interesting variation in the excitation spectra. The particles also have a wide range of potential uses, such as examining particle uptake activity of a macrophage cell line, also demonstrated. The nanoparticles were coated with albumin to provide functionality for potential conjugation to biological targeting agents

View Article
January 2012
9 Reads

Enhancement of the growth and differentiation of nasal olfactory mucosa cells by the conjugation of growth factors to functional nanoparticles.

Bioconjug Chem 2011 Dec 17;22(12):2600-10. Epub 2011 Nov 17.

Department of Chemistry, Bar-Ilan Institute of Nanotechnology and Advanced Materials, Ramat-Gan, Israel.

View Article
December 2011
6 PubMed Central Citations(source)
4.51 Impact Factor

Synthesis, fluorescence and biodistribution of a bone-targeted near-infrared conjugate.

Eur J Med Chem 2011 Oct 31;46(10):5175-83. Epub 2011 Aug 31.

Institute of Nanotechnology & Advanced Materials, Department of Chemistry, Bar-Ilan University, Ramat Gan, Israel.

View Article
October 2011
4 Reads
6 PubMed Central Citations(source)
3.45 Impact Factor

Enhancement of incisional wound healing by thrombin conjugated iron oxide nanoparticles.

Biomaterials 2010 Feb 21;31(4):741-7. Epub 2009 Oct 21.

Department of Chemistry, Bar-Ilan University, Ramat-Gan, Israel.

View Article
February 2010
3 Reads
13 PubMed Central Citations(source)
8.56 Impact Factor

Synthesis and Characterization of Thrombin Conjugated γ-Fe2O3 Magnetic Nanoparticles for Hemostasis

Advanced Engineering Materials, in Advanced Biomaterials, 2009, 11(12): B251-B260

Advanced Engineering Materials, in Advanced Biomaterials

Thrombin is the final protease produced in the clotting pathways. Thrombin has been used in the clinic more than six decades for topical hemostasis and wound management. In human plasma the half-life of thrombin is shorter than 15 seconds due to close control by inhibitors. In order to stabilize thrombin, this enzyme was conjugated covalently and physically to g-Fe2O3 magnetic nanoparticles. The physical conjugation was accomplished through adsorption of thrombin to BSA coating on the nanoparticles. The coagulant activity of the covalently bound thrombin was significantly lower than that of the physically adsorbed thrombin. Leakage of the physically bound thrombin into PBS containing 4% HSA was negligible. The physical conjugation of thrombin onto the nanoparticles stabilized the thrombin against its major inhibitor antithrombin III and improved its storage stability. At optimal CaCl2 concentration, the clotting time by the bound thrombin is shorter than that of the free enzyme. This novel conjugated thrombin may be an efficient candidate for topical hemostasis and wound healing.

View Article
December 2009
7 Reads

Enhancement of incisional wound healing by thrombin conjugated iron oxide nanoparticles

Biomaterials 31 (2010) 741–747

Biomaterials

Thrombin has been clinically used for topical hemostasis and wound management for more than six decades. The half-life of thrombin in human plasma is shorter than 15 s due to close control by inhibitors. In order to stabilize the thrombin, it was bound to maghemite (gama-Fe2O3) nanoparticles, as demonstrated in previous work. The aim of the present study was to examine the efficiency of the bound thrombin for wound healing applications compared to the free thrombin. For this purpose incisional wounds on rat skin were treated with a mixture of fibrinogen, CaCl2 solution and free or bound thrombin. The wounds’ edges were then approximated by skin staples. The control incisional wounds were closed with staples only. In the course of 28 days of healing the highest values of skin tensile strength were observed following treatment with the bound thrombin. Significantly lower values of tensile strength were observed following treatment with the free thrombin, and the lowest values were obtained following treatment with staples only. The histological findings correlate with the mechanical strength measurements, which demonstrate the most advanced stages of healing following treatment with the bound thrombin.

View Article
October 2009
10 Reads

Immunogenicity of Bioactive Magnetic Nanoparticles: Natural and Acquired Antibodies

J Biomed Mater Res A. 2008 Jun 15;85(4):1011-21

Journal of Biomedical Materials Research Part A

Uniform magnetic nanoparticles (MNP) were prepared by nucleation followed by controlled growth of maghemite thin films onto porcine gelatin nuclei. The formed gelatin containing MNP (Gel-MNP) were then coated with dextran (Gel-MNP-Dex) followed by human serum albumin (Gel-MNP-Dex-HSA). Since these MNP are designated for clinical applications, studies concerning the immunogenicity of their antigenic components (porcine gelatin, dextran, and HSA) have been performed in BALB-C mice. These studies demonstrated that plasma of nonimmunized mice already contains basal levels of natural antibodies against all of these antigenic components. This work also demonstrated that the conjugated gelatin is a weak immunogen: Intraperitoneal injection of the various MNP (Gel-MNP, Gel-MNP-Dex dispersed in PBS emulsified with Incomplete Freund’s Adjuvant (IFA) mineral oil and Gel-MNP-Dex-HSA dispersed in PBS) did not increase significantly the acquired anti-gelatin antibody titers. Exceptional behavior was observed following immunization with Gel-MNP-Dex-HSA dispersed in PBS emulsified with IFA, which exhibited an adjuvant effect and turned gelatin into a stronger immunogen. In contrast to gelatin, the conjugated HSA and dextran were found to be strong immunogens. The possibility that the various MNP will not induce an autoimmune response as a result of their clinical use is discussed in the contest of the protective role of the natural antibodies.

View Article
June 2008
7 Reads