50 research outputs found
Surface Modification of Melt Extruded Poly(ε-caprolactone) Nanofibers: Toward a New Scalable Biomaterial Scaffold.
A photochemical modification of melt-extruded polymeric nanofibers is described. A bioorthogonal functional group is used to decorate fibers made exclusively from commodity polymers, covalently attach fluorophores and peptides, and direct cell growth. Our process begins by using a layered coextrusion method, where poly(ε-caprolactone) (PCL) nanofibers are incorporated within a macroscopic poly(ethylene oxide) (PEO) tape through a series of die multipliers within the extrusion line. The PEO layer is then removed with a water wash to yield rectangular PCL nanofibers with controlled cross-sectional dimensions. The fibers can be subsequently modified using photochemistry to yield a "clickable" handle for performing the copper-catalyzed azide-alkyne cycloaddition (CuAAC) reaction on their surface. We have attached fluorophores, which exhibit dense surface coverage when using ligand-accelerated CuAAC reaction conditions. In addition, an RGD peptide motif was coupled to the surface of the fibers. Subsequent cell-based studies have shown that the RGD peptide is biologically accessible at the surface, leading to increased cellular adhesion and spreading versus PCL control surfaces. This functionalized coextruded fiber has the advantages of modularity and scalability, opening a potentially new avenue for biomaterials fabrication
Combinatorial Synthesis, Screening, and Binding Studies of Highly Functionalized Polyamino-amido Oligomers for Binding to Folded RNA
Folded RNA molecules have recently emerged as critical regulatory elements in biological pathways, serving not just as carriers of genetic information but also as key components in enzymatic assemblies. In particular, the transactivation response element (TAR) of the HIV genome regulates transcriptional elongation by interacting specifically with the Tat protein, initiating the recruitment of the elongation complex. Preventing this interaction from occurring in vivo halts HIV replication, thus making RNA-binding molecules an intriguing pharmaceutical target. Using α-amino acids as starting materials, we have designed and synthesized a new class of polyamino-amido oligomers, called PAAs, specifically for binding to folded RNA structures. The PAA monomers were readily incorporated into a 125-member combinatorial library of PAA trimers. In order to rapidly assess RNA binding, a quantum dot-based fluorescent screen was developed to visualize RNA binding on-resin. The binding affinities of hits were quantified using a terbium footprinting assay, allowing us to identify a ligand (SFF) with low micromolar affinity (kd=14 μM) for TAR RNA. The work presented herein represents the development of a flexible scaffold that can be easily synthesized, screened, and subsequently modified to provide ligands specific for binding to folded RNAs
Synthesis and Studies of Non-Natural Oligomers that Interact with Biomolecules: PNA, Polyamines, and Peptoids
Cell Engineering with Functional Poly(oxanorbornene) Block Copolymers
Cell-based therapies are gaining prominence in treating a wide variety of diseases and using synthetic polymers to manipulate these cells provides an opportunity to impart function that could not be achieved using solely genetic means. Herein, we describe the utility of functional block copolymers synthesized by ring-opening metathesis polymerization (ROMP) that can insert directly into the cell membrane via the incorporation of long alkyl chains into a short polymer block leading to non-covalent, hydrophobic interactions with the lipid bilayer. Furthermore, we demonstrate that these polymers can be imbued with advanced functionalities. A photosensitizer was incorporated into these polymers to enable spatially controlled cell death by the localized generation of (1)O(2) at the cell surface in response to red-light irradiation. In a broader context, we believe our polymer insertion strategy could be used as a general methodology to impart functionality onto cell-surfaces
Optimization of ring-opening metathesis polymerization (ROMP) under physiologically relevant conditions
Ring opening metathesis polymerization (ROMP) is widely considered an excellent living polymerization technique that proceeds rapidly under ambient conditions and is highly functional group tolerant when performed in organic solvents. However, achieving the same level of success in aqueous media has proved to be challenging, often requiring an organic co-solvent or a very low pH to obtain fast initiation and high monomer conversion. The ability to efficiently conduct ROMP under neutral pH aqueous conditions would mark an important step towards utilizing aqueous ROMP with acid-sensitive functional groups or within a biological setting. Herein we describe our efforts to optimize ROMP in an aqueous environment under neutral pH conditions. Specifically, we found that the presence of excess chloride in solution as well as relatively small changes in pH near physiological conditions have a profound effect on molecular weight control, polymerization rate and overall monomer conversion. Additionally, we have applied our optimized conditions to polymerize a broad scope of water-soluble monomers and used this methodology to produce nanostructures via ring opening metathesis polymerization induced self-assembly (ROMPISA) under neutral pH aqueous conditions
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Recent advancements in single dose slow‐release devices for prophylactic vaccines
Single dose slow-release vaccines herald a new era in vaccine administration. An ideal device for slow-release vaccine delivery would be minimally invasive and self-administered, making these approaches an attractive alternative for mass vaccination programs, particularly during the time of a pandemic. In this review article, we discuss the latest advances in this field, specifically for prophylactic vaccines able to prevent infectious diseases. Recent studies have found that slow-release vaccines elicit better immune responses and often do not require cold chain transportation and storage, thus drastically reducing the cost, streamlining distribution, and improving efficacy. This promise has attracted significant attention, especially when poor patient compliance of the standard multidose vaccine regimes is considered. Single dose slow-release vaccines are the next generation of vaccine tools that could overcome most of the shortcomings of present vaccination programs and be the next platform technology to combat future pandemics. This article is categorized under: Therapeutic Approaches and Drug Discovery > Emerging Technologies Implantable Materials and Surgical Technologies > Nanomaterials and Implants Biology-Inspired Nanomaterials > Protein and Virus-Based Structures
Analysis of Polymer-Biomacromolecule Composites in the Solid-State via Energy Dispersive Spectroscopy-Scanning Electron Microscopy
pH Responsive Doxorubicin Delivery by Fluorous Polymers for Cancer Treatment
Polymeric nanoparticles have emerged
as valuable drug delivery
vehicles as they improve solubility of hydrophobic drugs, enhance
circulation lifetime, and can improve the biodistribution profile
of small-molecule therapeutics. These nanoparticles can take on a
host of polymer architectures including polymersomes, hyperbranched
nanoparticles, and dendrimers. We have recently reported that simple
low molecular weight fluorous copolymers can self-assemble into nanoparticles
and show exceptional passive targeting into multiple tumor models.
Given the favorable biodistribution of these particles, we sought
to develop systems that enable selective delivery in acidic environments,
such as the tumor microenvironment or the lysosomal compartment. In
this report, we describe the synthesis and <i>in vitro</i> biological studies of a pH-responsive doxorubicin (DOX) fluorous
polymer conjugate. A propargyl DOX hydrazone was synthesized and covalently
attached to a water-dispersible fluorous polymer composed of trifluoroethyl
methacrylate (TFEMA) and oligo(ethylene glycol) methyl ether methacrylate
(OEGMEMA) using the ligand-accelerated copper-catalyzed azide–alkyne
cycloaddition. Driven by the high fluorine content of the copolymer
carrier, the DOX–copolymer formed stable micelles under aqueous
conditions with a hydrodynamic diameter of 250 nm. The DOX–copolymer
showed internalization into multiple <i>in vitro</i> models
for breast and ovarian cancer. Cytotoxicity assays demonstrated efficacy
in both breast and ovarian cancer with overall efficacy being highly
dependent on the cell line chosen. Taken together, these results present
a platform for the pH-triggered delivery of DOX from a fluorous micelle
carrier effective against multiple cancer models <i>in vitro</i>
“Graft-to” Protein/Polymer Conjugates Using Polynorbornene Block Copolymers
A series of water-soluble polynorbornene
block copolymers prepared
via Ring-Opening Metathesis Polymerization (ROMP) were grafted to
proteins to form ROMP-derived bioconjugates. ROMP afforded low-dispersity
polymers and allowed for strict control over polymer molecular weight
and architecture. The polymers consisted of a large block of PEGylated
monoester norbornene and were capped with a short block of norbornene
dicarboxylic anhydride. This cap served as a reactive linker that
facilitated attachment of the polymer to lysine residues under mildly
alkaline conditions. The generality of this approach was shown by
synthesizing multivalent polynorbornene-modified viral nanoparticles
derived from bacteriophage Qβ, a protein nanoparticle used extensively
for nanomedicine. The conjugated nanoparticles showed no cytotoxicity
to NIH 3T3 murine fibroblast cells. These findings establish protein
bioconjugation with functionalized polynorbornenes as an effective
alternative to conventional protein/polymer modification strategies
and further expand the toolbox for protein bioconjugates