3 research outputs found
Cross-linked Polymer Nanofibers for Hyperthermophilic Enzyme Immobilization: Approaches to Improve Enzyme Performance
We
report an enzyme immobilization method effective at elevated temperatures
(up to 105 °C) and sufficiently robust for hyperthermophilic
enzymes. Using a model hyperthermophilic enzyme, α-galactosidase
from Thermotoga maritima, immobilization
within chemically cross-linked polyÂ(vinyl alcohol) (PVA) nanofibers
to provide high specific surface area is achieved by (1) electrospinning
a blend of a PVA and enzyme and (2) chemically cross-linking the polymer
to entrap the enzyme within a water insoluble PVA fiber. The resulting
enzyme-loaded nanofibers are water-insoluble at elevated temperatures,
and enzyme leaching is not observed, indicating that the cross-linking
effectively immobilizes the enzyme within the fibers. Upon immobilization,
the enzyme retains its hyperthermophilic nature and shows improved
thermal stability indicated by a 5.5-fold increase in apparent half-life
at 90 °C, but with a significant decrease in apparent activity.
The loss in apparent activity is attributed to enzyme deactivation
and mass transfer limitations. Improvements in the apparent activity
can be achieved by incorporating a cryoprotectant during immobilization
to prevent enzyme deactivation. For example, immobilization in the
presence of trehalose improved the apparent activity by 10-fold. Minimizing
the mat thickness to reduce interfiber diffusion was a simple and
effective method to further improve the performance of the immobilized
enzyme
Layer-by-Layer Nanoparticles for Systemic Codelivery of an Anticancer Drug and siRNA for Potential Triple-Negative Breast Cancer Treatment
A single nanoparticle platform has been developed through the modular and controlled layer-by-layer process to codeliver siRNA that knocks down a drug-resistance pathway in tumor cells and a chemotherapy drug to challenge a highly aggressive form of triple-negative breast cancer. Layer-by-layer films were formed on nanoparticles by alternately depositing siRNA and poly-l-arginine; a single bilayer on the nanoparticle surface could effectively load up to 3500 siRNA molecules, and the resulting LbL nanoparticles exhibit an extended serum half-life of 28 h. In animal models, one dose <i>via</i> intravenous administration significantly reduced the target gene expression in the tumors by almost 80%. By generating the siRNA-loaded film atop a doxorubicin-loaded liposome, we identified an effective combination therapy with siRNA targeting multidrug resistance protein 1, which significantly enhanced doxorubicin efficacy by 4 fold <i>in vitro</i> and led to up to an 8-fold decrease in tumor volume compared to the control treatments with no observed toxicity. The results indicate that the use of layer-by-layer films to modify a simple liposomal doxorubicin delivery construct with a synergistic siRNA can lead to significant tumor reduction in the cancers that are otherwise nonresponsive to treatment with Doxil or other common chemotherapy drugs. This approach provides a potential strategy to treat aggressive and resistant cancers, and a modular platform for a broad range of controlled multidrug therapies customizable to the cancer type in a singular nanoparticle delivery system
PEG–Polypeptide Block Copolymers as pH-Responsive Endosome-Solubilizing Drug Nanocarriers
Herein
we report the potential of click chemistry-modified polypeptide-based
block copolymers for the facile fabrication of pH-sensitive nanoscale
drug delivery systems. PEG–polypeptide copolymers with pendant
amine chains were synthesized by combining <i>N</i>-carboxyanhydride-based
ring-opening polymerization with post-functionalization using azide–alkyne
cycloaddition. The synthesized block copolymers contain a polypeptide
block with amine-functional side groups and were found to self-assemble
into stable polymersomes and disassemble in a pH-responsive manner
under a range of biologically relevant conditions. The self-assembly
of these block copolymers yields nanometer-scale vesicular structures
that are able to encapsulate hydrophilic cytotoxic agents like doxorubicin
at physiological pH but that fall apart spontaneously at endosomal
pH levels after cellular uptake. When drug-encapsulated copolymer
assemblies were delivered systemically, significant levels of tumor
accumulation were achieved, with efficacy against the triple-negative
breast cancer cell line, MDA-MB-468, and suppression of tumor growth
in an in vivo mouse model