Synthetic polycations with controlled charge density and molecular weight as building blocks for biomaterials

<p>A series of polycations prepared by RAFT copolymerization of N-(3-aminopropyl)methacrylamide hydrochloride (APM) and N-(2-hydroxypropyl)methacrylamide, with molecular weights of 15 and 40 kDa, and APM content of 10–75 mol%, were tested as building blocks for electrostatically assembled hydrogels such as those used for cell encapsulation. Complexation and distribution of these copolymers within anionic calcium alginate gels, as well as cytotoxicity, cell attachment, and cell proliferation on surfaces grafted with the copolymers were found to depend on composition and molecular weight. Copolymers with lower cationic charge density and lower molecular weight showed less cytotoxicity and cell adhesion, and were more mobile within alginate gels. These findings aid in designing improved polyelectrolyte complexes for use as biomaterials.</p

Charge-Shifting Polycations with Tunable Rates of Hydrolysis: Effect of Backbone Substituents on Poly[2-(dimethylamino)ethyl acrylates]

While polycations based on 2-(dimethylamino)­ethyl methacrylate and 2-(dimethylamino)­ethyl acrylate are used in applications ranging from biomaterials to wastewater treatment, few studies have considered the remarkable differences in the hydrolytic stabilities of the respective ester groups. Here, we describe how the nature of nonmethyl α-substituents affect the rates of ester hydrolysis of such polymers, with an emphasis on the resulting shift of net polymer charge from cationic toward anionic. We introduce 2-(dimethylamino)­ethyl 2-hydroxymethyl acrylate (DHMA) as a new, very hydrolytically labile, cationic monomer that can be used to form homopolymers as well as a means to tune copolymer hydrolysis. DHMA synthesis and free radical polymerization are described, including reactivity ratios for hydroxyl-protected derivatives of DHMA and 2-(dimethylamino)­ethyl acrylate (DMAEA). Hydrolyses of PDHMA, P­[DHMA-<i>co</i>-DMAEA], PDMAEA, and PDMAEMA in pH 5 and 7 buffer are reported. The presence of the hydroxymethyl α-substituent in PDHMA led to rates of hydrolysis 2–3 orders of magnitude faster than the already rapid hydrolysis of PDMAEA. Furthermore, hydrolysis rates of P­[DHMA-<i>co</i>-DMAEA] copolymers were shown to increase as the DHMA mole fraction increased. As a result, a new route to adjusting the charge-shifting rates of such polycations in aqueous media is described

Tunable Hydrogel Thin Films from Reactive Synthetic Polymers as Potential Two-Dimensional Cell Scaffolds

This article describes the formation of cross-linked 10–200-nm-thick polymer hydrogel films by alternating the spin-coating of two mutually reactive polymers from organic solutions, followed by hydrolysis of the resulting multilayer film in aqueous buffer. Poly­(methyl vinyl ether-<i>alt</i>-maleic anhydride) (PMM) was deposited from acetonitrile solution, and poly­(<i>N</i>-3-aminopropylmethacrylamide-<i>co</i>-<i>N</i>-2-hydroxypropylmethacrylamide) (PAPM<i>_x</i>, where <i>x</i> corresponds to the 3-aminopropylmethacrylamide content ranging from 10 to 100%) was deposited from methanol. Multilayer films were formed in up to 20 deposition cycles. The films cross-linked during formation by reaction between the amine groups of PAPM<i>_x</i> and the anhydride groups of PMM. The resulting multilayer films were covalently postfunctionalized by exposure to fluoresceinamine, decylamine, d-glucamine, or fluorescently labeled PAPM<i>_x</i> solutions prior to the hydrolysis of residual anhydride in aqueous PBS buffer. This allowed tuning the hydrophobicity of the film to give static water contact angles ranging from about 5 to 90°. Increasing the APM content in PAPM<i>_x</i> from 10 to 100% led to apparent Young’s moduli from 300 to 700 kPa while retaining sufficient anhydride groups to allow postfunctionalization of the films. This allowed the resulting (PMM/PAPM<i>_x</i>) multilayer films to be turned into adhesion-promoting or antifouling surfaces for C2C12 mouse myoblasts and MCF 10A premalignant human mammary epithelial cells