Synthetic, Functional Thymidine-Derived Polydeoxyribonucleotide Analogues from a Six-Membered Cyclic Phosphoester

A grand challenge that crosses synthetic chemistry and biology is the scalable production of functional analogues of biomacromolecules. We have focused our attention on the use of deoxynucleoside building blocks bearing non-natural bases to develop a synthetic methodology that allows for the construction of high molecular weight deoxynucleotide polymers. Our six-membered cyclic phosphoester ring-opening polymerization strategy is demonstrated, herein, by an initial preparation of novel polyphosphoesters, comprised of butenyl-functionalized deoxyribonucleoside repeat units, connected via 3′,5′-backbone linkages. A thymidine-derived bicyclic monomer, 3′,5′-cyclic 3-(3-butenyl) thymidine ethylphosphate, was synthesized in two steps directly from thymidine, via butenylation and diastereoselective cyclization promoted by <i>N</i>,<i>N</i>-dimethyl-4-aminopyridine. Computational modeling of the six-membered 3′,5′-cyclic phosphoester ring derived from deoxyribose indicated strain energies at least 5.4 kcal/mol higher than those of the six-membered monocyclic phosphoester, 2-ethoxy-1,3,2-dioxaphosphinane 2-oxide. These calculations supported the hypothesis that the strained 3′,5′-cyclic monomer can promote ring-opening polymerization to afford the resulting poly­(3′,5′-cyclic 3-(3-butenyl) thymidine ethylphosphate)­s with low dispersities (<i><i>Đ</i></i> < 1.10). This advanced design combines the merits of natural product-derived materials and functional, degradable polymers to provide a new platform for functional, synthetically derived polydeoxyribonucleotide-analogue materials

Correction to “Synthetic, Functional Thymidine-Derived Polydeoxyribonucleotide Analogues from a Six-Membered Cyclic Phosphoester”

Correction to “Synthetic, Functional Thymidine-Derived Polydeoxyribonucleotide Analogues from a Six-Membered Cyclic Phosphoester

Self-Reporting Degradable Fluorescent Grafted Copolymer Micelles Derived from Biorenewable Resources

A series of hydrolytically degradable fluorescent poly­(ferulic acid-<i>co</i>-tyrosine)-<i>g</i>-<i>m</i>PEG graft copolymers were synthesized and shown to undergo self-assembly in aqueous media to yield fluorescent micelles. The polymers and their micellar assemblies exhibited greater fluorescence emission intensity than did their small molecular building blocks, which provides a self-reporting character that has potential for monitoring the polymer integrity and also for performing in theranostics applications. The amphiphilic <i>graft</i>-copolymers were synthesized by Cu-assisted azide–alkyne “click” addition of azido-functionalized <i>m</i>PEG polymers onto fluorescent degradable hydrophobic copolymers displaying randomly distributed alkyne side-chain groups along their biorenewably derived poly­(ferulic acid-<i>co</i>-tyrosine) backbones. The morphologies and photophysical properties of the supramolecular assemblies generated in aqueous solutions were evaluated by DLS, TEM, AFM, and steady-state optical spectroscopies. The 15–30 nm sized micelles behaved as broad-band emitters in the 350–600 nm range, which highlights their potential as self-reporting nanomaterials for in vitro studies

Amphiphilic Cross-Linked Liquid Crystalline Fluoropolymer-Poly(ethylene glycol) Coatings for Application in Challenging Conditions: Comparative Study between Different Liquid Crystalline Comonomers and Polymer Architectures

Linear and hyperbranched poly­(ethylene glycol)-cross-linked amphiphilic fluoropolymer networks comprised of different liquid crystalline comonomers were developed and evaluated as functional coatings in extreme weather-challenging conditions. Through variation of the liquid-crystalline comonomer and hydrophilic:hydrophobic component ratios, several series of coatings were synthesized and underwent a variety of analyses including differential scanning calorimetry, water contact angle measurements and solution stability studies in aqueous media. These materials maintained an unprecedented reduction in the free water melting transition (<i>T</i>_m) temperature across the hyperbranched and linear versions. The coatings synthesized from hyperbranched fluoropolymers preserved the liquid crystalline character of the mesogenic components, as seen by polarized optical microscopy, and demonstrated stability in saltwater aqueous environments and in cold weather conditions

Functional Polycarbonate of a d‑Glucal-Derived Bicyclic Carbonate via Organocatalytic Ring-Opening Polymerization

Herein, we demonstrate the synthesis of a bicyclic carbonate monomer of a d-glucal derivative, which originated from the natural product d-glucose, in an efficient three-step procedure and its ring-opening polymerization (ROP), initiated by 4-methylbenzyl alcohol, via organocatalysis. The ROP behavior was studied as a function of time, catalyst type, and catalyst concentration by using size exclusion chromatography (SEC) and nuclear magnetic resonance (NMR) spectroscopy. Using a cocatalyst system of 1,8-diazabicyclo[5.4.0]­undec-7-ene and 1-(3,5-bis­(trifluoromethyl)­phenyl)-3-cyclohexyl-2-thiourea (5 mol %) afforded poly­(d-glucal-carbonate) (PGCC) with almost complete monomer conversion (ca. 99%) within 1 min, as analyzed by ¹H NMR spectroscopy, and a monomodal SEC trace with dispersity of 1.13. The resulting PGCCs exhibited amorphous characteristics with a relatively high glass transition temperature at ca. 69 °C and onset decomposition temperature at ca. 190 °C, as analyzed by differential scanning calorimetry and thermogravimetric analysis, respectively. This new type of potentially degradable polymer system represents a reactive functional polymer architecture

Regioisomeric Preference in Ring-Opening Polymerization of 3′,5′-Cyclic Phosphoesters of Functional Thymidine DNA Analogues

Regioregularity is a crucial property in the synthesis of DNA analogues, as natural DNA is synthesized exclusively in the 5′ to 3′ direction. We have focused our attention on the determination of the regioisomeric distribution of poly­(3′,5′-cyclic 3-(3-butenyl) thymidine ethylphosphate)­s obtained from the ring-opening polymerization of (<i>R</i>)-3′,5′-cyclic 3-(3-butenyl) thymidine ethylphosphate. The regioisomeric preference was investigated by comparison to synthesized model compounds of 3′,3′-, 3′,5′-, and 5′,5′-linkages, where the model 3′-phosphoester linkages were to the secondary alcohol of 3-hydroxytetrahydrofuran and the model 5′-linkages derived from coupling to the primary alcohol of tetrahydrofurfuryl alcohol. From the ³¹P resonance frequency assignments of those small molecule model compounds, ³¹P NMR spectra revealed the major connectivity in the polymer backbone to be 3′,5′-linkages, with ≤30% of other isomeric forms. Model reactions employing a series of alcohol initiators imparting various degrees of steric hindrance, to mimic the increased steric hindrance of the propagating alcohol relative to the initiator, were then conducted to afford the corresponding ring-opened unimer adducts and to gain understanding of the regioselectivity during the ring-opening polymerization. ¹H–³¹P heteronuclear multiple-bond correlation spectroscopy showed ethanol and 4-methoxybenzyl alcohol initiation to yield only the P–O5′ bond cleavage product, whereas attack by isopropyl alcohol upon (<i>R</i>)-3′,5′-cyclic 3-(3-butenyl) thymidine ethylphosphate afforded both P–O3′ and P–O5′ bond cleavage products, supporting our hypothesis that the increased steric hindrance of the propagating species dictates the regioselectivity of the P–O bond cleavage. Further model reactions suggested that the P–O5′ bond cleavage products can be detected upon the formation of dimers during the ring-opening polymerization. Overall, this work provides a fundamental understanding of the polymerization behavior of six-membered cyclic phosphoesters and broadens the scope of DNA analogues from the ring-opening polymerization of 3′,5′-cyclic phosphoesters

Degradability of Poly(Lactic Acid)-Containing Nanoparticles: Enzymatic Access through a Cross-Linked Shell Barrier

Comparative studies of bulk samples of hydrolytically degradable poly­(lactic acid) (PLA) vs core–shell block copolymer micelles having PLA cores revealed remarkable acceleration in the proteinase K enzymatic hydrolysis of the nanoparticulate forms and demonstrated that even with amidation-based shell cross-linking the core domain remained accessible. Kinetic analyses by ¹H NMR spectroscopy showed less than 20% lactic acid released from enzymatically catalyzed hydrolysis of poly­(l-lactic acid) in bulk, whereas ca. 70% of the core degraded within 48 h for block copolymer micelles of poly­(<i>N</i>-(acryloyloxy)­succinimide-<i>copolymer</i>-<i>N</i>-acryloylmorpholine)-<i>block</i>-poly­(L-lactic acid) (P­(NAS-<i>co</i>-NAM)-<i>b</i>-PLLA), with only a slight reduction to ca. 50% for the shell cross-linked derivatives. Rigorous characterization measurements by NMR spectroscopy, fluorescence spectroscopy, dynamic light scattering, atomic force microscopy, and transmission electron microscopy were employed to confirm core excavation. These studies provide important fundamental understanding of the effects of nanoscopic dimensions on protein–polymer interactions and polymer degradability, which will guide the development of these degradable nanoconstructs to reach their potential for controlled release of therapeutics and biological clearance

Dynamic Anti-Icing Coatings: Complex, Amphiphilic Hyperbranched Fluoropolymer Poly(ethylene glycol) Cross-Linked Networks with an Integrated Liquid Crystalline Comonomer

Amphiphilic hyperbranched fluoropolymer coatings incorporating liquid crystalline moieties and poly­(ethylene glycol) cross-linkers were found to demonstrate noteworthy anti-icing properties. A series of amphiphilic networks was synthesized through variation of the polymer molecular weights and hydrophilic/hydrophobic component ratios. These innovative materials show a remarkable reduction in the free water melting transition (<i>T</i>_m) temperature (−10 °C), measured by differential scanning calorimetry, and an increase in water contact angle for dry and water-swollen systems. The addition of this ordered parameter generated a unique coating topography, which can be visualized via polarized optical microscopy and 3D optical microscopy, while maintaining an overall macroscopic homogeneity

Hyperbranched Fluoropolymer-Polydimethylsiloxane-Poly(ethylene glycol) Cross-Linked Terpolymer Networks Designed for Marine and Biomedical Applications: Heterogeneous Nontoxic Antibiofouling Surfaces

Synthesis of terpolymer coatings composed of hyperbranched fluoropolymers cross-linked with bisamino-propyl poly­(ethylene glycol) and bisamino-propyl polydimethylsiloxane (PDMS) was performed to generate antibiofouling surfaces. Nanoscale imaging and surface spectroscopy confirmed that this system possessed complex surface topographies and chemical compositions. Surface complexity was determined to be due to molecular interactions, phase segregation, and compositional gradients arising between the three components. A clear difference in surface behavior was observable before and after exposure to water. Antibiofouling characteristics were investigated by bovine serum albumin (BSA) adsorption studies; the terpolymer coating displayed a 60% greater resistance to protein adsorption in comparison to the fouling of a commercial antibiofouling silicone coating. The unique surface topography, topology, and chemical heterogeneity expressed at a variety of scales provide a robust regime for the generation of hardy, complex surfaces known to incorporate characteristics appropriate for antibiofouling applications. Thorough assessment of thermal responses and mechanical properties in relevant environments demonstrated a formulation platform immediately appropriate for consideration in marine and in vivo applications

Poly(ferulic acid-<i>co</i>-tyrosine): Effect of the Regiochemistry on the Photophysical and Physical Properties en Route to Biomedical Applications

The photophysical and mechanical properties of novel poly­(carbonate-amide)­s derived from two biorenewable resources, ferulic acid (FA) and l-tyrosine ethyl ester, were evaluated in detail. From these two bio-based precursors, a series of four monomers were generated (having amide and/or carbonate coupling units with remaining functionalities to allow for carbonate formation) and transformed to a series of four poly­(carbonate-amide)­s. The simplest monomer, which was biphenolic and was obtained in a single amidation synthetic step, displayed bright, visible fluorescence that was twice brighter than FA. Multidimensional fluorescence spectroscopy of the polymers in solution highlighted the strong influence that regioselectivity and the degree of polymerization have on their photophysical properties. The regiochemistry of the system had little effect on the wettability, surface free energy, and Young’s modulus (ca. 2.5 GPa) in the solid state. Confocal imaging of solvent-cast films of each polymer revealed microscopically flat surfaces with fluorescent emission deep into the visible region. Fortuitously, one of the two regiorandom polymers (obtainable from the biphenolic monomer in only an overall two synthetic steps from FA and l-tyrosine ethyl ester) displayed the most promising fluorescent properties both in the solid state and in solution, allowing for the possibility of translating this system as a self-reporting or imaging agent in future applications. To further evaluate the potential of this polymer as a biodegradable material, hydrolytic degradation studies at different pH values and temperatures were investigated. Additionally, the antioxidant properties of the degradation products of this polymer were compared with its biphenolic monomer and FA