Heteroacene-Based Amphiphile as a Molecular Scaffold for Bioimaging Probes

The challenges faced with current fluorescence imaging agents have motivated us to study two nanostructures based on a hydrophobic dye, 6H-pyrrolo[3,2-b:4,5-b’]bis [1,4]benzothiazine (TRPZ). TRPZ is a heteroacene with a rigid, pi-conjugated structure, multiple reactive sites, and unique spectroscopic properties. Here we coupled TRPZ to a tert-butyl carbamate (BOC) protected 2,2-bis(hydroxymethyl)propanoic acid (bisMPA) dendron via azide-alkyne Huisgen cycloaddition. Deprotection of the protected amine groups on the dendron afforded a cationic terminated amphiphile, TRPZ-bisMPA. TRPZ-bisMPA was nanoprecipitated into water to obtain nanoparticles (NPs) with a hydrodynamic radius that was \u3c150 nm. For comparison, TRPZ-PG was encapsulated in pluronic-F127 (Mw = 12 kD), a polymer surfactant to afford NPs almost twice as large as those formed by TRPZ-bisMPA. Size and stability studies confirm the suitability of the TRPZ-bisMPA NPs for biomedical applications. The photophysical properties of the TRPZ-bisMPA NPs show a quantum yield of 49%, a Stokes shift of 201 nm (0.72 eV) and a lifetime of 6.3 ns in water. Further evidence was provided by cell viability and cellular uptake studies confirming the low cytotoxicity of TRPZ-bisMPA NPs and their potential in bioimaging

AMPHIPHILIC JANUS POLYMER NANOPARTICLES FOR PHARMACEUTICAL AND BIOMEDICAL APPLICATIONS

Amphiphilic hybrid polymers have attracted significant interest as biomaterials for both fundamental research and practical clinical applications due to their unique polymer structure and properties relative to the conventional symmetric polymers. Often referred to as “Janus” polymers combine two different polymer segments (hydrophilic and hydrophobic) of varying degrees, sizes, and functionalities to obtain a single amphiphilic or hetero-functional macromolecule with characteristic features. In particular, amphiphilic “Janus” polymers and their self-assemblies have shown apparent success in nanomedicine owing to their ability to provide highly ordered nanoscale multimolecular aggregates, including micelles and vesicles. However, engineering these polymeric materials on a large scale with nanoaggregates of desirable size and morphology remains challenging. Herein novel synthetic routes and characterization for amphiphilic Janus polymer libraries and their nanoaggregates are presented. The first library discusses the design, synthesis, and characterization of self-assembling amphiphilic Janus dendrimers, which consisted of NH3+ (cationic), COO- (anionic), and OH (neutral) polyamidoamine (PAMAM) as hydrophilic segments and fatty acid branches as the hydrophobic segment. The results of this study afford opportunities to evaluate in-vivo efficacy as well as stability and interactions with bloodstream components. The second system involves in-situ self-assembly, known as polymerization-induced self-assembly (PISA). Using the PISA approach, we designed the first cationic dendritic macro chain transfer agent to synthesize a Janus-type hybrid polymer called a linear dendritic block copolymer (LDBCs). These studies offer a one-pot polymerization method for a new class of fluorinated Janus-type LDBC for a 19F magnetic resonance imaging (MRI) agent. These results showcase novel yet efficient pathways toward building next-generation biomaterials with unique morphologies and tunable properties

Cross-linking Poly(caprolactone)–Polyamidoamine Linear Dendritic Block Copolymers for Theranostic Nanomedicine

This study represents a comparative analysis of the solution behavior and self-assembly pattern of two linear dendritic block copolymers (LDBCs) composed of a generation 3 polyamidoamine (PAMAM) dendron as the dendritic block and poly(caprolactone) (PCL) as the linear block, the latter of which is modified with pendant phenyl groups. Phenyl substituents were introduced to induce physical cross-linking in LDBC nanoparticles via π–π stacking. A synthetic strategy was developed to access phenyl substituted LDBCs through an ε-caprolactone monomer derivative followed by ring-opening polymerization to form a library of LDBCs with yields above 83%. Polymersome-like nanoparticles were observed in water with a 74.4 nm average diameter. Cross-linked LDBC nanoparticles demonstrated a 37.1% relative decrease in the critical aggregation concentration (CAC) and a 27.3–41.2% relative increase of hydrophobic loading efficiency relative to unsubstituted LDBCs. Nanoparticles loaded with a potential photothermal agent (phenyl indolizine-C5 (C5)) showed a photothermal efficiency of 49.4% with a heating temperature of 44.4 °C. These nanoparticles were efficiently loaded into HEK293 cells with cell viability above 87.5% at the highest concentration. Upon illumination with red light, nanoparticles loaded with photothermal agent were able to induce cell death in cancer cells. This work suggests that the phenyl substituted LDBCs form nanoparticles with enhanced stability and loading efficiencies compared to conventional nonphenylated systems and display a greater potential to be used as nanocarriers in theranostic nanomedicine

Improved Nanoformulation and Bio-Functionalization of Linear-Dendritic Block Copolymers With Biocompatible Ionic Liquids

Linear-dendritic block copolymers (LDBCs) have emerged as promising materials for drug delivery applications, with their hybrid structure exploiting advantageous properties of both linear and dendritic polymers. LDBCs have promising encapsulation efficiencies that can be used to encapsulate both hydrophobic and hydrophilic dyes for bioimaging, cancer therapeutics, and small biomolecules. Additionally, LDBCS can be readily functionalized with varying terminal groups for more efficient targeted delivery. However, depending on structural composition and surface properties, LDBCs also exhibit high dispersities (Đ), poor shelf-life, and potentially high cytotoxicity to non-target interfacing blood cells during intravenous drug delivery. Here, we show that choline carboxylic acid-based ionic liquids (ILs) electrostatically solvate LDBCs by direct dissolution and form stable and biocompatible IL-integrated LDBC nano-assemblies. These nano-assemblies are endowed with red blood cell-hitchhiking capabilities and show altered cellular uptake behavior ex vivo. When modified with choline and trans-2-hexenoic acid, IL-LDBC dispersity dropped by half compared to bare LDBCs, and showed a significant shift of the cationic surface charge towards neutrality. Proton nuclear magnetic resonance spectroscopy evidenced twice the total amount of IL on the LDBCs relative to an established IL-linear PLGA platform. Transmission electron microscopy suggested the formation of a nanoparticle surface coating, which acted as a protective agent against RBC hemolysis, reducing hemolysis from 73% (LDBC) to 25% (IL-LDBC). However, dramatically different uptake behavior of IL-LDBCs vs. IL-PLGA NPs in RAW 264.7 macrophage cells suggests a different conformational IL-NP surface assembly on the linear versus the linear-dendritic nanoparticles. These results suggest that by controlling the physical chemistry of polymer-IL interactions and assembly on the nanoscale, biological function can be tailored toward the development of more effective and more precisely targeted therapies

Synthesis and characterization of polylactide‐PAMAM “Janus‐type” linear‐dendritic hybrids

© 2019 Wiley Periodicals, Inc. Herein, we present a facile and comprehensive synthetic methodology for the preparation of polyester-polyamidoamine (PAMAM) (i.e., polyester: polylactide [PLA] (hydrophobic) and polyamidoamine, PAMAM [hydrophilic]) polymers. A library of PLA-PAMAM linear dendritic block copolymers (LDBCs) in which both l and d, l polylactide were employed in mass ratios of 30:70, 50:50, 70:30, and 90:10 (PLA:PAMAM) were synthesized and analyzed. When placed in aqueous media, the immiscibility of the hydrophilic and hydrophobic segments leads to nanophase-segregation exhibited as the formation of aggregates (e.g., vesicles, worms, and/or micelles). By employing both stereochemical configurations of PLA, the differentiation in mass ratios of PLA-PAMAM aided in elucidating the structure–property relationships of the LDBC system and provided a means toward the control of nanoparticle morphology. Transmission electron microscopy and dynamic light scattering afford the size and shape of the nanoparticles with diameters ranging from 10.6 for low mass ratios to 122.4 nm for high mass ratios of PLA-PAMAM and positive zeta-potential values between +24.7 mV and +48.2 mV. Furthermore, small-angle X-ray scattering (SAXS) studies were employed to obtain more detailed information on the morphological assemblies constructed via direct dissolution. Such insights provide a pathway toward nanomaterials with unique morphologies and tunable properties deemed relevant in the development of next generation biomaterials. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019, 57, 1448–1459

Self-Assembling PCL-PAMAM Linear Dendritic Block Copolymers (LDBCs) for Bioimaging and Phototherapeutic Applications

Copyright © 2020 American Chemical Society. This study represents a successful approach toward employing polycaprolactone-polyamidoamine (PCL-PAMAM) linear dendritic block copolymer (LDBC) nanoparticles as small-molecule carriers in NIR imaging and photothermal therapy. A feasible and robust synthetic strategy was used to synthesize a library of amphiphilic LDBCs with well-controlled hydrophobic-to-hydrophilic weight ratios. Systems with a hydrophobic weight ratio higher than 70% formed nanoparticles in aqueous media, which show hydrodynamic diameters of 51.6 and 96.4 nm. These nanoparticles exhibited loading efficiencies up to 21% for a hydrophobic molecule and 64% for a hydrophilic molecule. Furthermore, successful cellular uptake was observed via trafficking into endosomal and lysosomal compartments with an encapsulated NIR theranostic agent (C3) without inducing cell death. A preliminary photothermal assessment resulted in cell death after treating the cells with encapsulated C3 and exposing them to NIR light. The results of this work confirm the potential of these polymeric materials as promising candidates in theranostic nanomedicine