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Primary amine containing copolymer, poly(N,N-dimethylacrylamide-co-N-(3-aminopropyl)methacrylamide hydrochloride) (poly(DMA-co-APMA)), brushes were synthesized on Ti surface by surface-initiated atom transfer radical polymerization (SI-ATRP) in aqueous conditions. A series of poly(DMA-co-APMA) copolymer brushes on titanium (Ti) surface with different molecular weights, thicknesses, compositions, and graft densities were synthesized by changing the SI-ATRP reaction conditions. Cysteine-functionalized cationic antimicrobial peptide Tet213 (KRWWKWWRRC) was conjugated to the copolymers brushes using a maleimide-thiol addition reaction after initial modification of the grafted chains using 3-maleimidopropionic acid N-hydroxysuccinimide ester. The modified surfaces were characterized by X-ray photoelectron spectroscopy (XPS), water contact angle measurements, attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy, atomic force microscopy (AFM), and ellipsometry analysis. The conjugation of the Tet213 onto brushes strongly depended on graft density of the brushes at different copolymer brush compositions. The peptide density (peptides/nm(2)) on the surface varied with the initial composition of the copolymer brushes. Higher graft density of the brushes generated high peptide density (pepetide/nm(2)) and lower number of peptides/polymer chain and vice versa. The peptide density and graft density of the chains on surface greatly influenced the antimicrobial activity of peptide grafted polymer brushes against Pseudomonas aeruginosa.

The present study deals with the synthesis and polymerization of novel amino acid-derived acetylene monomers, N-(tert-butoxycarbonyl)-l-alanine N‘-propargylamide (L-1A), N-(tert-butoxycarbonyl)-l-alanine N‘-methyl-N ‘-propargylamide (N-Me-L-1A), and N-(tert-butoxycarbonyl)-l-alanine propargyl ester (L-1E) and the analysis of the properties of the formed polymers. The monomers were synthesized by the condensation of N-(tert-butoxycarbonyl)-l-alanine with propargylamine, N-methylpropargylamine, and propargyl alcohol in 50, 89, and 72% yields, respectively. They satisfactorily underwent polymerization with (nbd)Rh+[η6-C6H5B-(C6H5)3] as a catalyst ([M]0/[Cat] = 10−200) in THF and CH2Cl2 at 0−50 °C to afford the corresponding polymers with M n's in the range 1 × 104−2 × 105. Poly(L-1A) exhibited a large specific rotation {[α]D = −1349° (CH2Cl2)} and a CD signal ([θ]max = −3.2 × 104 deg cm2 dmol-1 (CHCl3), suggesting that it takes a helical conformation. On the other hand, poly(N-Me-1A) and poly(L-1E) showed no evidence of a helical structure. The helical structure of poly(L-1A) was deformed by the addition of MeOH.

Dissecting the mechanism of action of surface-tethered antimicrobial and immunomodulatory peptides is critical to the design of optimized anti-infection coatings on biomedical devices. To address this, we compared the biomembrane interactions of host defense peptide IDR-1010cys (1) in free form, (2) as a soluble polymer conjugate, and (3) with one end tethered to a solid support with model bacterial and mammalian lipid membranes. Our results show that IDR-1010cys in all three distinct forms interacted with bacterial and mammalian lipid vesicles, but the extent of the interactions as monitored by the induction of secondary structure varied. The enhanced interaction of surface-tethered peptides is well correlated with their very good antimicrobial activities. Our results demonstrate that there may be a difference in the mechanism of action of surface-tethered versus free IDR-1010cys.

A series of ionic responsive poly(N-isopropylacrylamide) (PNIPAM) surface-modified lignin nanofiber mats were prepared by aqueous surface-initiated atom transfer radical polymerization (SI-ATRP). PNIPAM brushes with various molecular weights, thickness, and grafting densities were immobilized on electrospun lignin nanofiber mats by adjusting initial monomer concentration and surface initiator density. ATR-FTIR, SEM, TGA, XPS, and water contact angle measurements confirmed successful surface modification. Analysis of the PNIPAM-modified lignin nanofiber mats (Lig-PN) found that the lower critical solution temperature (LCST) was similar to that of PNIPAM and demonstrated ionic responsive characteristics. With increasing ionic concentration, the water contact angles of the Lig-PN increased correspondingly. AFM images showed that the PNIPAM on the lignin nanofiber mat surface expanded in water and contracted in 0.5 M Na(2)SO(4).

N-Propargylamide-terminated peptide-based macromonomers with a degree of polymerization ranging from 4 to 40 were synthesized by the polymerization of gamma-benzyl and gamma-stearyl-L-glutamate-N-carboxy anhydrides initiated with propargylamine. The macromonomers took an alpha-helical structure, which was confirmed by signals at 208 and 220 nm in CD spectra. The macromonomers were subjected to polymerization and copolymerization with an alanine-derived N-propargylamide [N-(tert-butoxycarbonyl)-L-alanine-N'-propargylamide] catalyzed with (2,5-norbornadiene)Rh+[eta6-C6H5B- (C6H5)3]. It was confirmed through a CD spectroscopic study that the copolymer obtained from the copolymerization of the gamma-stearyl-L-glutamate-based macromonomer with the alanine-derived N-propargylamide had a helical polyacetylene main chain and helical polypeptide side chains.

The present study deals with the copolymerization of an amino acid-based acetylene, N-(tertbutoxycarbonyl)-L-alanine N′-propargylamide (L-1A) with the optical isomer (D-1A), achiral hexanoic acid N-propargylamide (2A), and pivalic acid N-propargylamide (3A), and chiroptical properties of the copolymers. The copolymerization catalyzed by (nbd)Rh + [η 6 -C6H5B -(C6H5)3] afforded copolymers with number-average molecular weights over 10 4 in good yields. Nonlinear relationships were observed in the specific rotation and CD and UV-vis spectroscopies with respect to the L-1A content in feed. For instance, poly(L-1A-co-D-1A)s incorporated with 12.5% of either optical isomer (75% ee) exhibited almost the same optical properties as those of the homopolymers. Chiral amplification was observed in the copolymerization of L-1A with the achiral monomers. The specific rotation of poly(L-1A-co-2A) with 45% L-1A unit was practically the same as that of poly(L-1A). The copolymers of L-1A and 3A with an L-1A content in feed as low as 12% exhibited nearly the same helix content as the homopolymer of L-1A did.

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