3 research outputs found
Cross-Linked Hydrogels Formed through Diels–Alder Coupling of Furan- and Maleimide-Modified Poly(methyl vinyl ether-<i>alt</i>-maleic acid)
The
Diels–Alder [4 + 2] cycloaddition between furan- and
maleimide-functional polyanions was used to form cross-linked synthetic
polymer hydrogels. PolyÂ(methyl vinyl ether-<i>alt</i>-maleic
anhydride) was reacted with furfurylamine or <i>N</i>-(2-aminoethyl)Âmaleimide
in acetonitrile to form pairs of furan- and maleimide-functionalized
polyÂ(methyl vinyl ether-<i>alt</i>-maleic acid)Âs. Mixtures
of these mutually reactive polyanions in water gelled within 15 min
to 18 h, depending on degree of functionalization and polymer concentrations.
Solution and magic-angle spinning <sup>1</sup>H NMR were used to confirm
the formation of the Diels–Alder adduct, to analyze competing
hydrolytic side reactions, and demonstrate postgelation functionalization.
The effect of the degree of furan and maleimide functionalization,
polymer concentration, pH, and calcium ion concentration, on gelation
time, gel mechanical properties, and equilibrium swelling, are described.
Release of dextran as a model drug was studied using fluorescence
spectroscopy, as a function of gel composition and calcium treatment
Charge-Shifting Polycations with Tunable Rates of Hydrolysis: Effect of Backbone Substituents on Poly[2-(dimethylamino)ethyl acrylates]
While polycations
based on 2-(dimethylamino)Âethyl methacrylate
and 2-(dimethylamino)Âethyl 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)Âethyl 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)Âethyl acrylate (DMAEA). Hydrolyses of PDHMA,
PÂ[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 PÂ[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. PolyÂ(methyl vinyl
ether-<i>alt</i>-maleic anhydride) (PMM) was deposited from
acetonitrile solution, and polyÂ(<i>N</i>-3-aminopropylmethacrylamide-<i>co</i>-<i>N</i>-2-hydroxypropylmethacrylamide) (PAPM<i><sub>x</sub></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><sub>x</sub></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><sub>x</sub></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><sub>x</sub></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><sub>x</sub></i>) multilayer films to be turned into adhesion-promoting or antifouling
surfaces for C2C12 mouse myoblasts and MCF 10A premalignant human
mammary epithelial cells