End-Group Engineering in Amphiphilic Segmented Polyurethanes: Strong Impact on Hierarchical Self-Assembled Structure and Antibacterial Activity.

A series of amphiphilic polyurethanes were synthesized by condensation polymerization between hexyl-diisocyanate and Boc-protected serinol in the presence of a chain-stopper R-OH ( = short hydrocarbon chain). Deprotection of the Boc group produced amphiphilic polymers with pendant amine groups, which, at pH ∼5, adopted an intrachain H-bonding-stabilized pleated structure. Hierarchical assembly of such folded chains produced unilamellar vesicles with excellent surface display of the amine groups.

Complex Sequence-Defined Heteropolymers Enable Controlled Film Growth in Layer-By-Layer Assembly.

Digitally-encoded poly(phosphodiesters) (d-PPDE) with highly complex primary structures are evaluated for layer-by-layer (LbL) assembly. To be easily decoded by mass spectrometry (MS), these digital polymers contain many different monomers: 2 coding units allowing binary encryption, 1 cleavable spacer allowing controlled MS fragmentation, and 3 mass tags allowing fragment identification. These complex heteropolymers are therefore composed of 6 different motifs.

Hierarchical assembly of foldable polymers and applications in organic optoelectronics and antibacterial or antiviral materials.

Aggregation of amphiphilic polymers in block-selective solvents produces different nanostructures, which have been studied extensively for wide-ranging applications. Nevertheless, such immiscibility-driven aggregation does not endow them with the desired structural precision, predictability or surface functional group exposure, which significantly impact their functional applications. More recently, biomimetic folded structures of synthetic macromolecules (mostly oligomers) have come to the fore, but such studies have been limited to probe the secondary structures.

Cisplatin-Conjugated Polyurethane Capsule for Dual Drug Delivery to a Cancer Cell.

This paper describes the synthesis of a polymer-prodrug conjugate, its aqueous self-assembly, noncovalent encapsulation of a second drug, and stimuli-responsive intracellular dual drug delivery. Condensation polymerization between a functionalized diol and a commercially available diisocyanate in the presence of poly(ethylene glycol) hydroxide (PEG-OH) as the chain stopper produces an ABA-type amphiphilic block copolymer (PU-1) in one pot, with the middle hydrophobic block being a polyurethane containing a pendant -butyloxycarbonyl (Boc)-protected amine in every repeating unit. Deprotection of the Boc group, followed by covalent attachment of the Pt(IV) prodrug using the pendant amine groups, produces the polymer-prodrug conjugate PU-Pt-1, which aggregates to nanocapsule-like structures in water with a hydrophilic interior.

Direct Correlation between the Secondary Structure of an Amphiphilic Polymer and Its Prominent Antiviral Activity.

An amphiphilic segmented polyurethane (F-PU-S), with pendant sulfate groups and a flexible hydrocarbon backbone, exhibits intrachain H-bonding-reinforced folding and hierarchical assembly, producing an anionic polymersome with efficient display of sulfate groups at the surface. It shows an excellent antiviral activity against Sendai virus (SV) by inhibiting its entry to the cells. Mechanistic investigation suggests fusion of the SV and the polymersome to produce larger particles in which neither the folded structure of the polymer nor the fusogenic property of the SV exists anymore.

Control over Multiple Nano- and Secondary Structures in Peptide Self-Assembly.

Herein, we report the rich morphological and conformational versatility of a biologically active peptide (PEP-1), which follows diverse self-assembly pathways to form up to six distinct nanostructures and up to four different secondary structures through subtle modulation in pH, concentration and temperature. PEP-1 forms twisted β-sheet secondary structures and nanofibers at pH 7.4, which transform into fractal-like structures with strong β-sheet conformations at pH 13.

Self-Assembled Polyurethane Capsules with Selective Antimicrobial Activity against Gram-Negative .

This article reports the antimicrobial activity of two segmented amphiphilic polyurethanes, PU-1 and PU-2, containing a primary or secondary amine group, respectively. In acidic water, intrachain H-bonding among the urethanes followed by hierarchical assembly resulted in the formation of capsules ( = 120 ± 20 and 100 ± 17 nm for PU-1 and PU-2, respectively) with a highly positive surface charge. They showed selective interactions with bacterial cell mimicking liposomes over mammalian cell mimicking liposomes with favorable enthalpy and entropy contributions, which was attributed to the electrostatic interaction and hydrophobic effect.

Tunable nanostructures by directional assembly of donor-acceptor supramolecular copolymers and antibacterial activity.

This manuscript reports supramolecular copolymerization of amphiphilic donor (D) and acceptor (A) units and their antibacterial activity. The donor unit (Py-1) contains a pyrene chromophore attached to a quaternary ammonium group by an amide linker. In the acceptor unit (NDI-1), a naphthalene-diimide (NDI) chromophore is attached to a hydrophilic non-ionic wedge and a benzamide group on its two opposite arms.

Synthesis and Self-assembly of a Helical Polymer Grafted from a Foldable Polyurethane Scaffold.

Herein a polyurethane graft poly-l-glutamate amphiphilic copolymer was synthesized from a polyurethane (PU)-based macro-initiator (containing pendant primary amine groups) through the ring opening polymerization of N-carboxy anhydride of γ-benzyl-l-glutamate (BLG-NCA). On average, twenty two l-glutamic acids were grafted from each amino group which was pendant on the polyurethane chain with 10 repeating units. The grafted polymer (PU-PP-1) exhibits self-assembly to produce a hydrogel in a wide pH window ranging from pH 5.

Directional Supramolecular Assembly of π-Amphiphiles with Tunable Surface Functionality and Impact on the Antimicrobial Activity.

This article elucidates H-bonding-regulated directional supramolecular assembly of naphthalene diimide (NDI)-derived unsymmetric cationic bola-shaped π-amphiphiles and systematic investigations on the thermodynamics of their interaction with bacteria mimic lipid vesicles and antimicrobial activity with mechanistic insights. Four NDI-amphiphiles (NDI-1, NDI-2, NDI-3, and NDI-2a) have been studied, all of which contain a central NDI chromophore, a nonionic wedge, an amine containing a head group, and a hydrazide group. In NDI-2 and NDI-2a, the hydrophilic wedge and the head group (pyridine) are the same but the location of the hydrazide group is different.

pH-Responsive Biocompatible Supramolecular Peptide Hydrogel.

Peptide-based hydrogels are highly promising for various biomedical applications owing to their precise self-assembly, biocompatibility, and sensitivity toward biologically relevant external stimuli. Herein, we report pH-responsive self-assembly and gelation of a highly biocompatible amphiphilic peptide PEP-1. This is an octa-peptide and double mutant of a naturally occurring β-strand peptide fragment of the protein Galectin-1, available in bovine spleen.