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In JoVE (1)
Other Publications (4)
Articles by Herbert P. Jennissen in JoVE
JoVE General
Chick ex ovo Culture and ex ovo CAM Assay: How it Really Works
1Institute for Physiological Chemistry, Department of Biochemical Endocrinology, University of Duisburg-Essen, 2Institute for Anatomy, Department of Neuroanatomy, University of Duisburg-Essen, 3Morphoplant GmbH, 4ARCONS Institute for Applied Research and Didactics
The chick chorioallantoic membrane (CAM) is a unique, naturally immunodeficient supportive culture environment to study angiogenesis and tumorigenesis. This video article demonstrates the different steps in chick ex ovo culture, application of potentially angiogenic substances and successful inoculation of tumor cells and tissues on the surface of the CAM.
Other articles by Herbert P. Jennissen on PubMed
Accelerated and Improved Osteointegration of Implants Biocoated with Bone Morphogenetic Protein 2 (BMP-2)
A concept and methodology are presented for the direct biocoating of implantable metals like titanium and stainless steel with bone morphogenetic protein 2 (BMP-2) for future applications as cementless bone or dental prostheses. Such bioactive surfaces can influence cells and tissues by chemotactic as well as juxtacrine mechanisms. Reference is made to first experiments in sheep and rabbits in which BMP-2 coatings impressively increased the osteoinductive potential of titanium implants.
Hydrophobic Interaction Chromatography: Harnessing Multivalent Protein-surface Interactions for Purification Procedures
Hydrophobic interaction chromatography (HIC) is one of the basic purification procedures in the biosciences. However, because of its complexity, it has not gained the same foothold in the methodological repertoire of protein chemistry as has affinity chromatography or ion exchange chromatography. This is mainly a result of the lack of a general optimization procedure for the reversible adsorption and elution of a novel protein to be purified. Further problems arise from the fact that most commercial hydrophobic adsorbents are inadequate for an ideal performance in downstream processing procedures, because these media are too hydrophobic and elution of proteins in their native state is often impossible. Therefore, as in the 1970s, a bioscientist of today has to be capable of synthesizing a small library of hydrophobic gels from which he or she can then select and optimize the ideal matrix for their special needs. In addition, a general optimization method employing the critical hydrophobicity concept has now been devised that should allow the application of HIC methodology to many hitherto unpurified proteins. In this chapter, the reader is first introduced to the theoretical background (multivalence, negative cooperativity, adsorption hysteresis) of the binding of protein ligands to hydrophobic supports, so that they will be capable of independently adapting HIC to a novel protein. Then a simple nontoxic method is described for the synthesis of HIC-gel libraries consisting of a homologous series of uncharged alkyl-Sepharoses of three chain lengths (butyl, pentyl, and hexyl Sepharose) prepared with different degrees of separation. From this series a critical hydrophobicity gel can then be selected and employed for critical hydrophobicity HIC. A detailed example for the chromatography of human fibrinogen is given that has been employed as a one-step procedure for the purification of fibrinogen from human plasma.
Interaction of Fibrinogen with N-alkylagaroses and Its Purification by Critical Hydrophobicity Hydrophobic Interaction Chromatograpy
A rational application of hydrophobic interaction chromatography (HIC) to the purification of proteins has remained an enigma in spite of over 30 years of research. The critical hydrophobicity parameter, which can be determined from a concentration series of n-alkyl Sepharose 4B (Seph-Cn) offers the possibility of adapting the HIC gel to the needs of purification. To this end a library of HIC gels (Seph-C4 to Seph-C6) of different immobilized alkyl residue concentrations was synthesized and tested with purified bovine fibrinogen. Binding of fibrinogen to such a concentration series resulted in sigmoidal binding curves. Analysis of the Seph-C5 data according to the lattices-site binding model yielded adsorption coefficients (nS) between 5 and 10 indicating that 5-10 lattice-sites (alkyl residues) interact multivalently with a fibrinogen molecule for adsorption at low ionic strength. The apparent lattice-site half-saturation constant of dissociation lies between 21 and 25 micromol/ml packed gel. For each alkyl chain length a critical hydrophobicity could be determined. For fibrinogen purification the critical hydrohobicity gel, Seph-C5 (13 micromol/ml packed gel), was selected. With the help of the cosolvents NaCl or glycine a fully reversible adsorption of fibrinogen could be facilitated on the critical hydrophobicity gel. Application of the method to human and bovine blood plasma resulted in a single step purification of fibrinogen in high yields. A comparison of the classical purification of fibrinogen with the critical hydrophobicity HIC (CHIC) method demonstrates a reduction in preparation time from several days to ca. 1 h. The subunit structure of HIC-purified human fibrinogen is identical to the classically purified protein. In the case of bovine fibrinogen however HIC-purified fibrinogen displayed a different subunit structure in that the Aalpha chain of fibrinogen had a ca. 5 kDa higher molecular mass. This may be due to the rapidity of the new one-step method and an avoidance of proteolysis.
Polyethylenimine-coated Albumin Nanoparticles for BMP-2 Delivery
Nanoparticle (NP)-based delivery has gained importance for improving the potency of therapeutic agents. The bovine serum albumin (BSA) NPs, obtained by a coacervation process, was modified by electrostatic adsorption of cationic polyethylenimine (PEI) to NP surfaces for delivery of bone-inducing growth factor, bone morphogenetic protein-2 (BMP-2). Different concentrations of PEI were utilized for coating BSA NPs to stabilize the colloidal system and to control the release of BMP-2. The NPs were characterized by size and zeta potential measurements, as well as by Scanning Electron Microscopy and Atomic Force Microscopy. The encapsulation efficiency was typically >90% in all NP preparations. In vitro release kinetics showed that the PEI concentration used for coating the NPs efficiently controlled the release of BMP-2, demonstrating a gradual slowing, sustained release pattern during a 10-day study period. The bioactivity of the encapsulated BMP-2 and the toxicity of the NPs were examined by the alkaline phosphatase (ALP) induction assay and the MTT assay, respectively, using C2C12 cells. The results indicated that PEI was the primary determinant of NP toxicities, and BSA NPs coated with 0.1 mg/mL PEI demonstrated tolerable toxicity, retained the bioactivity of BMP-2, and efficiently slowed the release rate of BMP-2. We conclude that BMP-2 encapsulated in BSA NPs might be an efficient way to deliver the protein for in vivo bone induction.
