title: Versatile Functionalization of Poly(methacrylic acid) Brushes with Series of Proteolytically Cleavable Peptides for Highly Sensitive Protease Assay.
abstract: The development of new materials for fast and sensitive protease assay is in demand for timely diagnosis of diseases, such as cardiovascular disease, cancers, and Alzheimer disease. Herein, poly(methacrylic acid) (PMAA) brushes were synthesized from the surfaces of silica nanoparticles via surface-initiated atom transfer radical polymerization (ATRP), and functionalized with series of proteolytically cleavable peptides for highly sensitive protease assay. Upon the proteolytic cleavage of the peptides, a short peptide fragment with fluorescent tag (GGK-FITC) is released to the solution, which can be easily detected with a benchtop fluorescence microscope. The grafting densities of PMAA brushes and peptides can be readily tuned by controlling the monomer concentrations of sodium methacrylate in the ATRP reaction. Because of the three-dimensional architecture of PMAA brushes, the loading amount of peptides can reach 21.4% of the total weight of functionalized silica particles (22.4 peptides/nm2), which is much higher than direct immobilization on silica nanoparticles without polymer brushes. Because of the high loading density of peptides, the limit of detection (LOD) of trypsin can reach 1.4 pM in buffer solution or 2.6 nM in nondiluted serum. By rational design of peptide substrates, the peptide-functionalized PMAA brushes can be readily expanded to detect other proteases, such as matrix metalloproteinase-2 (MMP-2), a virtual biomarker for many cancers, with an LOD of 1.1 pM. The proteolytically cleavable peptide-functionalized PMAA brushes offer a starting point for fast and sensitive protease assay.
authors.affiliation: State Key Laboratory of Chemical Resource Engineering, §Key Laboratory of Carbon Fiber and Functional Polymers, Ministry of Education, and ⊥Beijing Laboratory of Biomedical Materials, Beijing Advanced Innovation Center for Soft Matter Science and Engineering, Beijing University of Chemical Technology , Beijing 100029, China.
authors.forename: Yeping
authors.initials: Y
authors.lastname: Wu
authors.affiliation: State Key Laboratory of Chemical Resource Engineering, §Key Laboratory of Carbon Fiber and Functional Polymers, Ministry of Education, and ⊥Beijing Laboratory of Biomedical Materials, Beijing Advanced Innovation Center for Soft Matter Science and Engineering, Beijing University of Chemical Technology , Beijing 100029, China.
authors.forename: Anzhi
authors.initials: A
authors.lastname: Wang
authors.affiliation: State Key Laboratory of Chemical Resource Engineering, §Key Laboratory of Carbon Fiber and Functional Polymers, Ministry of Education, and ⊥Beijing Laboratory of Biomedical Materials, Beijing Advanced Innovation Center for Soft Matter Science and Engineering, Beijing University of Chemical Technology , Beijing 100029, China.
authors.forename: Xiaokang
authors.initials: X
authors.lastname: Ding
authors.affiliation: State Key Laboratory of Chemical Resource Engineering, §Key Laboratory of Carbon Fiber and Functional Polymers, Ministry of Education, and ⊥Beijing Laboratory of Biomedical Materials, Beijing Advanced Innovation Center for Soft Matter Science and Engineering, Beijing University of Chemical Technology , Beijing 100029, China.
authors.forename: Fu-Jian
authors.identifier: 0000-0002-1838-8811
authors.initials: FJ
authors.lastname: Xu
mesh_terms: D006801:Humans; D020778:Matrix Metalloproteinase 2; D008689:Methacrylates; D010455:Peptides / Q000378:metabolism*; D058105:Polymerization
chemical_list: D008689:Methacrylates; D010455:Peptides; C008384:methacrylic acid; D020778:Matrix Metalloproteinase 2
keywords: ATRP; PMAA; peptide; polymer brush; protease assay