title: Dextrin-rhEGF conjugates as bioresponsive nanomedicines for wound repair.
abstract: Growth factors are known to act in concert to promote wound repair, but their topical application rarely leads to a significant clinical improvement of chronic wounds due to premature inactivation in wound environment. The aim of this study was to synthesise a polymer-growth factor conjugate and investigate whether the novel concept called Polymer-masking-UnMasking-Protein Therapy (PUMPT) might be used to generate bioresponsive polymer therapeutics as nanomedicines able to promote tissue repair. Succinoylated dextrin ( approximately 85,000 g/mol; approximately 19 mol% succinoylation), and rhEGF were chosen as a first model combination. The conjugate synthesised contained approximately 16%wt rhEGF and <1% free protein. It exhibited increased stability towards proteolytic degradation by trypsin and the clinically relevant enzyme neutrophil elastase. The dextrin component was degraded on addition of alpha-amylase leading to sustained release of free rhEGF over time (52.7% release after 168 h). When biological activity was assessed (+/-alpha-amylase) in proliferation assays using epidermoid carcinoma (HEp2) cells and HaCaT keratinocytes, as anticipated, polymer conjugation reduced rhEGF bioactivity (p=0.0035). However, exposure to physiological concentrations of alpha-amylase triggered dextrin degradation and this led to protein unmasking with restoration of bioactivity to the level seen for unmodified rhEGF. Indeed, prolongation of HEp2 proliferation was observed over 8 days. The inability of dextrin, succinoylated dextrin or alpha-amylase alone to induce proliferative effects, and the ability of alpha-amylase-exposed dextrin-rhEGF to induce phosphorylation of the epidermal growth factor receptor (EGFR) in HEp2 cells confirmed a mechanism of action by stimulation of classical signal transduction pathways. These observations suggest that this dextrin-rhEGF, and other dextrin-growth factor conjugates have potential for further development as bioresponsive nanomedicines for tissue repair.
authors.affiliation: Wound Biology Group, Cardiff Institute of Tissue Engineering and Repair, Tissue Engineering and Reparative Dentistry, School of Dentistry, Heath Park Campus, Cardiff University, Cardiff, UK. hardwickej@cardiff.ac.uk
authors.forename: Joseph
authors.initials: J
authors.lastname: Hardwicke
authors.forename: Elaine L
authors.initials: EL
authors.lastname: Ferguson
authors.forename: Ryan
authors.initials: R
authors.lastname: Moseley
authors.forename: Phil
authors.initials: P
authors.lastname: Stephens
authors.forename: David W
authors.initials: DW
authors.lastname: Thomas
authors.forename: Ruth
authors.initials: R
authors.lastname: Duncan
mesh_terms: D055162:Biocatalysis; D002460:Cell Line; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D003692:Delayed-Action Preparations / Q000138:chemical synthesis / Q000737:chemistry / Q000494:pharmacology; D003912:Dextrins / Q000737:chemistry*; D016503:Drug Delivery Systems / Q000379:methods*; D004355:Drug Stability; D004815:Epidermal Growth Factor / Q000008:administration & dosage* / Q000737:chemistry / Q000494:pharmacology; D066246:ErbB Receptors / Q000378:metabolism; D006801:Humans; D015603:Keratinocytes / Q000166:cytology / Q000187:drug effects; D007700:Kinetics; D019272:Leukocyte Elastase / Q000737:chemistry; D008970:Molecular Weight; D050997:Nanomedicine / Q000379:methods*; D010766:Phosphorylation / Q000187:drug effects; D011355:Prodrugs / Q000138:chemical synthesis / Q000737:chemistry* / Q000494:pharmacology; D011994:Recombinant Proteins / Q000008:administration & dosage / Q000737:chemistry / Q000494:pharmacology; D017550:Spectroscopy, Fourier Transform Infrared; D013387:Succinic Anhydrides / Q000737:chemistry; D014945:Wound Healing / Q000187:drug effects / Q000502:physiology*; D000516:alpha-Amylases / Q000737:chemistry
chemical_list: D003692:Delayed-Action Preparations; D003912:Dextrins; D011355:Prodrugs; D011994:Recombinant Proteins; D013387:Succinic Anhydrides; D004815:Epidermal Growth Factor; C031801:succinic anhydride; C512478:EGFR protein, human; D066246:ErbB Receptors; D000516:alpha-Amylases; D019272:Leukocyte Elastase