Synthesis and characterization of cinnamated Type I collagen and its related mechanical properties after photomediated crosslinking were investigated in detail. Using an EDC/NHS conjugation method, collagen was chemically modified to incorporate a photosensitive cinnamate moiety. The cinnamated collagen was fully characterized by 1H NMR, UV-vis, and circular dichroism (CD) spectroscopy, as well as by rheological and mechanical analyses. Cinnamated collagens with varying degrees of derivatization retained collagen triple helical structure. The rheological spectra of collagen solutions demonstrate that the storage modulus decreases with increasing cinnamate content, owing to a decrease in physical crosslinking. The kinetics of the crosslinking process in both hydrated gels and dry films were monitored by UV-vis spectroscopy and confirmed that crosslinking was complete within 60 min of irradiation. The uniaxial stress-strain behavior of crosslinked collagen films, including Young's modulus and ultimate tensile strength, was comparable to values reported for glutaraldehyde-crosslinked monomeric collagen films. These data demonstrate that derivatization of collagen with photosensitive cinnamate moieties provides a facile route for solid-state crosslinking, thereby improving the mechanical properties of collagen and enhancing the potential applicability of collagen-based materials in tissue engineering and drug delivery.

Both well defined star-shaped poly(3-caprolactone) having four arms (4sPCL) and six arms (6sPCL) and linear PCL having one arm (LPCL) and two arms (2LPCL) were synthesized and then used for the investigation of physical properties, isothermal and nonisothermal crystallization kinetics, and spherulitic growth. The maximal melting point, the cold crystallization temperature, and the degree of crystallinity of these PCL polymers decrease with the increasing number of polymer arms, and they have similar crystalline structure. The isothermal crystallization rate constant (K) of these PCL polymers is in the order of K2LPCLOKLPCLOK4sPCLOK6sPCL. Notably, the K of linear PCL decreases with the increasing molecular weight of polymer while that of star-shaped PCL inversely increases. The variation trend of K over the number of polymer arms or the molecular weight of polymer is consistent with the analyses of both nonisothermal crystallization kinetics and the spherulitic growth rate. These results indicate that both the number of polymer arms and the molecular weight of polymer mainly controlled the isothermal and nonisothermal crystallization rate constants, the spherulitic growth rate, and the spherulitic morphology of these PCL polymers.

Glycopolymer-polypeptide triblock copolymers of the structure, poly(L-alanine)-b-poly(2-cryloyloxyethyllactoside)-b-poly(L-alanine)(AGA), have been synthesized by sequential atom transfer radical polymerization (ATRP) and ring-opening polymerization (ROP). Controlled free radical polymerization of 2-O-acryloyloxyethoxyl-(2,3,4,6-tetra-O-acetyl-â-D-galactopyranosyl)-(1-4)-2,3,6-tri-O-acetyl-â-D-glucopyranoside (AEL) by ATRP with a dibromoxylene (DBX)/CuBr/bipy complex system was used to generate a central glycopolymer block. Telechelic glycopolymers with diamino end groups were obtained by end group transformation and subsequently used as macroinitiators for ROP of L-alanine N-carboxyanhydride monomers (Ala-NCA). Gel permeation chromatography (GPC) and nuclear magnetic resonance (NMR) spectroscopy analysis demonstrated that copolymer molecular weight and composition were controlled by both the molar ratios of the Ala-NCA monomer to macroinitiator and monomer conversion and exhibited a narrow distribution (Mw/Mn) 1.06-1.26). FT-IR spectroscopy of triblock copolymers revealed that the ratio of R-helix/â-sheet increased with poly(L-alanine) block length. Of note, transmission electron microscopy (TEM) demonstrated that selected amphiphilic glycopolymer-polypeptide triblock copolymers self-assemble in aqueous solution to form nearly spherical aggregates of several hundreds nanometer in diameter. Significantly, the sequential application of ATRP and ROP techniques provides an effective method for producing triblock copolymers with a central glycopolymer block and flanking polypeptide blocks of defined architecture, controlled molecular weight, and low polydispersity.

A series of derivatized arylamine initiators were used to generate chain-end functionalized glycopolymers by cyanoxyl-mediated free-radical polymerization. Significant features of this strategy include the capacity to produce polymers of low polydispersity (PDI < 1.5) under aqueous conditions using unprotected monomers bearing a wide range of functional groups. In addition, the presence of a phenyl ring simplifies calculation of polymer saccharide content and molar mass by 1H NMR. It is particularly noteworthy, however, that derivatized arylamine initiators in conjunction with the presence of a terminal cyanate group provide a convenient approach for synthesizing polymers with a variety of distinct functional groups at R and ö chain ends. In the process, the capacity to label glycopolymers or otherwise conjugate them to proteins or other molecules is greatly enhanced.

A new class of dendron-like polypeptide/linear poly(ε-caprolactone) block copolymers with asymmetrical topology (i.e., dendron-like poly(γ-benzyl-L-glutamate)/linear PCL copolymers having 2m PBLG branches, m) 0, 1, 2, and 3; denoted as PCL-Dm-PBLG) was for the first time synthesized via the combination of controlled ringopening polymerization (ROP) of ε-caprolactone, click chemistry, and the ROP of γ-benzyl-L-glutamate N-carboxyanhydride (BLG-NCA). The linear hydroxyl-terminated PCL (PCL-OH) was synthesized by controlled ROP of ε-caprolactone and then transformed into clickable azide-terminated PCL (PCL-N3). The PCL-N3 precursor was further click conjugated with propargyl focal point PAMAM-typed dendrons (i.e., Dm having 2m primary amine groups) to generate PCL-dendrons (PCL-Dm) using CuBr/PMDETA as catalyst in dimethylformamide solution at 35℃. Finally, PCL-Dm was used as macroinitiator for the ROP of BLG-NCA monomer to produce the targeted PCL-Dm-PBLG block copolymers. Their molecular structures and physical properties were characterized in detail by FT-IR, NMR, matrix assisted laser desorption ionization time-of-flight mass spectrometry, gel permeation chromatography, differential scanning calorimetry, and wide-angle X-ray diffraction. To the best of our knowledge, this is the first report that describes the synthesis of dendron-like polypeptide/linear PCL block copolymers with asymmetrical topology via the combination of ROP and click chemistry. Consequently, this provides a versatile strategy for the synthesis of biodegradable and biomimetic dendron-like polypeptide-based biohybrids.