title: Biodegradable insulin-loaded PLGA microspheres fabricated by three different emulsification techniques: investigation for cartilage tissue engineering.
abstract: Growth, differentiation and migration factors facilitate the engineering of tissues but need to be administered with defined gradients over a prolonged period of time. In this study insulin as a growth factor for cartilage tissue engineering and a biodegradable PLGA delivery device were used. The aim was to investigate comparatively three different microencapsulation techniques, solid-in-oil-in-water (s/o/w), water-in-oil-in-water (w/o/w) and oil-in-oil-in-water (o/o/w), for the fabrication of insulin-loaded PLGA microspheres with regard to protein loading efficiency, release and degradation kinetics, biological activity of the released protein and phagocytosis of the microspheres. Insulin-loaded PLGA microspheres prepared by all three emulsification techniques had smooth and spherical surfaces with a negative zeta potential. The preparation technique did not affect particle degradation nor induce phagocytosis by human leukocytes. The delivery of structurally intact and biologically active insulin from the microspheres was shown using circular dichroism spectroscopy and a MCF7 cell-based proliferation assay. However, the insulin loading efficiency (w/o/w about 80%, s/o/w 60%, and o/o/w 25%) and the insulin release kinetics were influenced by the microencapsulation technique. The results demonstrate that the w/o/w microspheres are most appropriate, providing a high encapsulation efficiency and low initial burst release, and thus these were finally used for cartilage tissue engineering. Insulin released from w/o/w PLGA microspheres stimulated the formation of cartilage considerably in chondrocyte high density pellet cultures, as determined by increased secretion of proteoglycans and collagen type II. Our results should encourage further studies applying protein-loaded PLGA microspheres in combination with cell transplants or cell-free in situ tissue engineering implants to regenerate cartilage.
authors.affiliation: Berlin-Brandenburg Center for Regenerative Therapies, Department of Rheumatology and Clinical Immunology, Charité-Universitätsmedizin Berlin, Berlin, Germany. kristin.andreas@charite.de
authors.forename: Kristin
authors.initials: K
authors.lastname: Andreas
authors.forename: Rolf
authors.initials: R
authors.lastname: Zehbe
authors.forename: Maja
authors.initials: M
authors.lastname: Kazubek
authors.forename: Karolina
authors.initials: K
authors.lastname: Grzeschik
authors.forename: Nadine
authors.initials: N
authors.lastname: Sternberg
authors.forename: Hans
authors.initials: H
authors.lastname: Bäumler
authors.forename: Helmut
authors.initials: H
authors.lastname: Schubert
authors.forename: Michael
authors.initials: M
authors.lastname: Sittinger
authors.forename: Jochen
authors.initials: J
authors.lastname: Ringe
mesh_terms: D001673:Biodegradation, Environmental / Q000187:drug effects; D002356:Cartilage / Q000502:physiology*; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D019902:Chondrocytes / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D002942:Circular Dichroism; D004655:Emulsions; D006025:Glycosaminoglycans / Q000378:metabolism; D006801:Humans; D006909:Hydroxyproline / Q000378:metabolism; D055767:Immobilized Proteins / Q000378:metabolism; D007150:Immunohistochemistry; D007328:Insulin / Q000737:chemistry / Q000494:pharmacology*; D019344:Lactic Acid / Q000737:chemistry*; D007962:Leukocytes / Q000166:cytology / Q000187:drug effects; D008855:Microscopy, Electron, Scanning; D008863:Microspheres; D010316:Particle Size; D010587:Phagocytosis / Q000187:drug effects; D011100:Polyglycolic Acid / Q000737:chemistry*; D000077182:Polylactic Acid-Polyglycolic Acid Copolymer; D055672:Static Electricity; D023822:Tissue Engineering / Q000379:methods*
chemical_list: D004655:Emulsions; D006025:Glycosaminoglycans; D055767:Immobilized Proteins; D007328:Insulin; D000077182:Polylactic Acid-Polyglycolic Acid Copolymer; D011100:Polyglycolic Acid; D019344:Lactic Acid; D006909:Hydroxyproline