Photoreduction of Graphene Oxide and Photochemical Synthesis of Graphene–Metal Nanoparticle Hybrids by Ketyl Radicals

The photoreduction of graphene oxide (GO) using ketyl radicals is demonstrated for the first time. The use of photochemical reduction through ketyl radicals generated by I-2959 or (1-[4-(2-hydroxyethoxy)­phenyl]-2-hydroxy-2-methyl-1-propan-1-one) is interesting because it affords spatial and temporal control of the reduction process. Graphene–metal nanoparticle hybrids of Ag, Au, and Pd were also photochemically fabricated in a one-pot procedure. Comprehensive spectroscopic and imaging techniques were carried out to fully characterize the materials. The nanoparticle hybrids showed promising action for the catalytic degradation of model environmental pollutants, namely, 4-nitrophenol, Rose Bengal, and Methyl Orange. The process described can be extended to polymer nanocomposites that can be photopatterned and could be potentially extended to fabricating plastic electronic devices

Synthesizing a Trefoil Knotted Block Copolymer via Ring-Expansion Strategy

A synthetic trefoil knotted poly­(ε-caprolatone)-<i>block</i>-poly­(l-lactide) (TK-PLA-<i>b</i>-PCL) is synthesized via a ring-expansion strategy from a trefoil knotted tin (Sn) initiator. Ring-closing reaction between the bis-copper­(I) templated phenanthroline complex and dibutyl­dimethoxytin results in a templated trefoil knotted initiator. The bis-copper­(I) templated trefoil knotted poly­(l-lactide) (TK-PLA) can be synthesized by ring-opening polymerization of l-lactide monomer, and decomplexation reaction of the templated TK-PLA will result in a geniune TK-PLA without constraint from the copper template. Subsequent insertion of ε-caprolactone in the bis-copper­(I) templated TK-PLA forms the templated trefoil knotted block copolymer, i.e., TK-PLA-<i>b</i>-PCL, and the copper-free TK-PLA-<i>b</i>-PCL can be obtained by decomplexation reaction. Both TK-PLA and TK-PLA-<i>b</i>-PCL are analyzed by the ¹H NMR, FT-IR, UV–vis, DLS, and GPC

Catenated Poly(ε-caprolactone) and Poly(l‑lactide) via Ring-Expansion Strategy

Catenated poly­(ε-caprolatone) (PCL) and poly­(l-lactide) (PLA) were synthesized by a ring-expansion strategy based on a catenated tin initiator. Catenated PCLs with different degrees of polymerization (DP_<i>n</i>) were obtained by modifying the feed ratios of monomer to initiator, and subsequent decomplexation rendered the copper-free catenated PCL. Both the Cu­(I)-templated catenated PCL and Cu­(I)-free catenated PCL were characterized by UV–vis, ¹H NMR, FT-IR, and GPC analyses. The comparative GPC analyses of catenated polymers and their linear analogues were also performed, which revealed a reduced hydrodynamic diameter for the catenated polymers. The crystallinity of the catenated PCL compared to that of linear PCL was also studied by DSC and WAXS, and the Cu­(I)-free catenated PCL exhibited a lower degree of crystallinity but larger crystallite size

3D Printing Biocompatible Polyurethane/Poly(lactic acid)/Graphene Oxide Nanocomposites: Anisotropic Properties

Blending thermoplastic polyurethane (TPU) with poly­(lactic acid) (PLA) is a proven method to achieve a much more mechanically robust material, whereas the addition of graphene oxide (GO) is increasingly applied in polymer nanocomposites to tailor further their properties. On the other hand, additive manufacturing has high flexibility of structure design which can significantly expand the application of materials in many fields. This study demonstrates the fused deposition modeling (FDM) 3D printing of TPU/PLA/GO nanocomposites and its potential application as biocompatible materials. Nanocomposites are prepared by solvent-based mixing process and extruded into filaments for FDM printing. The addition of GO largely enhanced the mechanical property and thermal stability of the nanocomposites. Interestingly, we found that the mechanical response is highly dependent on printing orientation. Furthermore, the 3D printed nanocomposites exhibit good biocompatibility with NIH3T3 cells, indicating promise as biomaterials scaffold for tissue engineering applications

High-Strength Stereolithographic 3D Printed Nanocomposites: Graphene Oxide Metastability

The weak thermomechanical properties of commercial 3D printing plastics have limited the technology’s application mainly to rapid prototyping. In this report, we demonstrate a simple approach that takes advantage of the metastable, temperature-dependent structure of graphene oxide (GO) to enhance the mechanical properties of conventional 3D-printed resins produced by stereolithography (SLA). A commercially available SLA resin was reinforced with minimal amounts of GO nanofillers and thermally annealed at 50 and 100 °C for 12 h. Tensile tests revealed increasing strength and modulus at an annealing temperature of 100 °C, with the highest tensile strength increase recorded at 673.6% (for 1 wt % GO). Thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) also showed increasing thermal stability with increasing annealing temperature. The drastic enhancement in mechanical properties, which is seen to this degree in 3D-printed samples reported in literature, is attributed to the metastable structure of GO, polymer–nanofiller cross-linking via acid-catalyzed esterification, and removal of intercalated water, thus improving filler–matrix interaction as evidenced by spectroscopy and microscopy analyses

Prostate-Specific Membrane Antigen Targeted Gold Nanoparticles for Theranostics of Prostate Cancer

Prostate cancer is one of the most common cancers and among the leading causes of cancer deaths in the United States. Men diagnosed with the disease typically undergo radical prostatectomy, which often results in incontinence and impotence. Recurrence of the disease is often experienced by most patients with incomplete prostatectomy during surgery. Hence, the development of a technique that will enable surgeons to achieve a more precise prostatectomy remains an open challenge. In this contribution, we report a theranostic agent (AuNP-5kPEG-PSMA-1-Pc4) based on prostate-specific membrane antigen (PSMA-1)-targeted gold nanoparticles (AuNPs) loaded with a fluorescent photodynamic therapy (PDT) drug, Pc4. The fabricated nanoparticles are well-characterized by spectroscopic and imaging techniques and are found to be stable over a wide range of solvents, buffers, and media. <i>In vitro</i> cellular uptake experiments demonstrated significantly higher nanoparticle uptake in PSMA-positive PC3pip cells than in PSMA-negative PC3flu cells. Further, more complete cell killing was observed in Pc3pip than in PC3flu cells upon exposure to light at different doses, demonstrating active targeting followed by Pc4 delivery. Likewise, <i>in vivo</i> studies showed remission on PSMA-expressing tumors 14 days post-PDT. Atomic absorption spectroscopy revealed that targeted AuNPs accumulate 4-fold higher in PC3pip than in PC3flu tumors. The nanoparticle system described herein is envisioned to provide surgical guidance for prostate tumor resection and therapeutic intervention when surgery is insufficient

Prostate-Specific Membrane Antigen Targeted Gold Nanoparticles for Theranostics of Prostate Cancer

Prostate cancer is one of the most common cancers and among the leading causes of cancer deaths in the United States. Men diagnosed with the disease typically undergo radical prostatectomy, which often results in incontinence and impotence. Recurrence of the disease is often experienced by most patients with incomplete prostatectomy during surgery. Hence, the development of a technique that will enable surgeons to achieve a more precise prostatectomy remains an open challenge. In this contribution, we report a theranostic agent (AuNP-5kPEG-PSMA-1-Pc4) based on prostate-specific membrane antigen (PSMA-1)-targeted gold nanoparticles (AuNPs) loaded with a fluorescent photodynamic therapy (PDT) drug, Pc4. The fabricated nanoparticles are well-characterized by spectroscopic and imaging techniques and are found to be stable over a wide range of solvents, buffers, and media. <i>In vitro</i> cellular uptake experiments demonstrated significantly higher nanoparticle uptake in PSMA-positive PC3pip cells than in PSMA-negative PC3flu cells. Further, more complete cell killing was observed in Pc3pip than in PC3flu cells upon exposure to light at different doses, demonstrating active targeting followed by Pc4 delivery. Likewise, <i>in vivo</i> studies showed remission on PSMA-expressing tumors 14 days post-PDT. Atomic absorption spectroscopy revealed that targeted AuNPs accumulate 4-fold higher in PC3pip than in PC3flu tumors. The nanoparticle system described herein is envisioned to provide surgical guidance for prostate tumor resection and therapeutic intervention when surgery is insufficient

3D Printing of Photocurable Cellulose Nanocrystal Composite for Fabrication of Complex Architectures via Stereolithography

The advantages of 3D printing on cost, speed, accuracy, and flexibility have attracted several new applications in various industries especially in the field of medicine where customized solutions are highly demanded. Although this modern fabrication technique offers several benefits, it also poses critical challenges in materials development suitable for industry use. Proliferation of polymers in biomedical application has been severely limited by their inherently weak mechanical properties despite their other excellent attributes. Earlier works on 3D printing of polymers focus mainly on biocompatibility and cellular viability and lack a close attention to produce robust specimens. Prized for superior mechanical strength and inherent stiffness, cellulose nanocrystal (CNC) from abaca plant is incorporated to provide the necessary toughness for 3D printable biopolymer. Hence, this work demonstrates 3D printing of CNC-filled biomaterial with significant improvement in mechanical and surface properties. These findings may potentially pave the way for an alternative option in providing innovative and cost-effective patient-specific solutions to various fields in medical industry. To the best of our knowledge, this work presents the first successful demonstration of 3D printing of CNC nanocomposite hydrogel via stereolithography (SL) forming a complex architecture with enhanced material properties potentially suited for tissue engineering