6 research outputs found
Shear Stress and Its Effect on the Interaction of Myoblast Cells with Nanosized Drug Delivery Vehicles
An important aspect to ensure progress
in biomedicine is the fundamental
understanding of the interaction of cells and tissue with (bio)materials.
The consideration of shear stress in drug delivery and/or tissue engineering
remains largely unexplored. To illustrate the fundamental relevance,
we employ a microfluidic setup to evaluate the myoblast cell response
to two prominent drug carrier systems, namely, liposomes and nanoparticles,
in the presence of low shear stress. We show that positively charged
carriers have an enhanced interaction with myoblast cells in the presence
of shear stress. This effect can be translated into improved therapeutic
response in terms of reduction in cell viability when delivering a
cytotoxic compound or into a better translocation efficiency when
using lipoplexes. Taken together, our fundamental findings open up
new possibilities in tissue engineering and drug delivery by considering
an additional parameter when delivering beneficial compounds
Confined Multiple Enzymatic (Cascade) Reactions within Poly(dopamine)-based Capsosomes
The design of compartmentalized carriers
as artificial cells is envisioned to be an efficient tool with potential
applications in the biomedical field. The advent of this area has
witnessed the assembly of functional, bioinspired systems attempting
to tackle challenges in cell mimicry by encapsulating multiple compartments
and performing controlled encapsulated enzymatic catalysis. Although
capsosomes, which consist of liposomes embedded within a polymeric
carrier capsule, are among the most advanced systems, they are still
amazingly simple in their functionality and cumbersome in their assembly.
We report on capsosomes by embedding liposomes within a poly(dopamine)
(PDA) carrier shell created in a solution-based single-step procedure.
We demonstrate for the first time the potential of PDA-based capsosomes
to act as artificial cell mimics by performing a two-enzyme coupled
reaction in parallel with a single-enzyme conversion by encapsulating
three different enzymes into separated liposomal compartments. In
the former case, the enzyme uricase converts uric acid into hydrogen
peroxide, CO<sub>2</sub> and allantoin, followed by the reaction of
hydrogen peroxide with the reagent Amplex Ultra Red in the presence
of the enzyme horseradish peroxidase to generate the fluorescent product
resorufin. The parallel enzymatic catalysis employs the enzyme ascorbate
oxidase to convert ascorbic acid into 2-<i>L</i>-dehydroascorbic
acid
Engineering Advanced Capsosomes: Maximizing the Number of Subcompartments, Cargo Retention, and Temperature-Triggered Reaction
Advanced mimics of cells require a large yet controllable number of subcompartments encapsulated within a scaffold, equipped with a trigger to initiate, terminate, and potentially restart an enzymatic reaction. Recently introduced capsosomes, polymer capsules containing thousands of liposomes, are a promising platform for the creation of artificial cells. Capsosomes are formed by sequentially layering liposomes and polymers onto particle templates, followed by removal of the template cores. Herein, we engineer advanced capsosomes and demonstrate the ability to control the number of subcompartments and hence the degree of cargo loading. To achieve this, we employ a range of polymer separation layers and liposomes to form functional capsosomes comprising multiple layers of enzyme-loaded liposomes. Differences in conversion rates of an enzymatic assay are used to verify that multilayers of intact enzyme-loaded liposomes are assembled within a polymer hydrogel capsule. The size-dependent retention of the cargo encapsulated within the liposomal subcompartments during capsosome assembly and its dependence on environmental pH changes are also examined. We further show that temperature can be used to trigger an enzymatic reaction at the phase transition temperature of the liposomal subcompartments, and that the encapsulated enzymes can be utilized repeatedly in several subsequent conversions. These engineered capsosomes with tailored properties present new opportunities <i>en route</i> to the development of functional artificial cells
One-Pot Green Synthesis of Biocompatible Graphene Quantum Dots and Their Cell Uptake Studies
Graphene-based quantum
dots (GQDs) are attractive fluorophores
due to their excellent photoluminescence properties, water solubility,
low cost, and low toxicity. However, the lack of simple, efficient,
and environmental-friendly synthesis methods often limits their biological
applications. Herein, we explore a novel, one-pot, green synthesis
approach for the fabrication of fluorescent GQDs without involving
any harsh reagents. Graphene oxide is used as a precursor, and a 2
h hydrothermal synthesis is carried out with assistance of hydrogen
peroxide; no further post purification steps are required. The effects
of reaction conditions on the characteristics of GQDs are comprehensively
investigated. The as-synthesized GQDs show a high photostability and
excellent biocompatibility as revealed by cell viability assays for
three different cell lines, namely, macrophages, endothelial cells,
and a model cancer cell line. The detailed studies of cellular uptake
mechanisms suggest that for all of the three cell lines the major
internalization route for GQDs is caveolae-mediated endocytosis followed
by clathrin-mediated endocytosis at a less extent. Our results demonstrate
the great potential of the as-synthesized GQDs as fluorescent nanoprobes.
The study also provides unique insight into the cell–GQDs interactions,
which is highly valuable for bioimaging and other related applications
such as diagnostics and drug delivery
Liposomes as Drug Deposits in Multilayered Polymer Films
The ex vivo growth of implantable
hepatic or cardiac tissue remains a challenge and novel approaches
are highly sought after. We report an approach to use liposomes embedded
within multilayered films as drug deposits to deliver active cargo
to adherent cells. We verify and characterize the assembly of poly(l-lysine) (PLL)/alginate, PLL/poly(l-glutamic acid),
PLL/poly(methacrylic acid) (PMA), and PLL/cholesterol-modified PMA
(PMA<sub>c</sub>) films, and assess the myoblast and hepatocyte adhesion
to these coatings using different numbers of polyelectrolyte layers.
The assembly of liposome-containing multilayered coatings is monitored
by QCM-D, and the films are visualized using microscopy. The myoblast
and hepatocyte adhesion to these films using PLL/PMA<sub>c</sub> or
poly(styrenesulfonate) (PSS)/poly(allyl amine hydrochloride) (PAH)
as capping layers is evaluated. Finally, the uptake of fluorescent
lipids from the surface by these cells is demonstrated and compared.
The activity of this liposome-containing coating is confirmed for
both cell lines by trapping the small cytotoxic compound thiocoraline
within the liposomes. It is shown that the biological response depends
on the number of capping layers, and is different for the two cell
lines when the compound is delivered from the surface, while it is
similar when administered from solution. Taken together, we demonstrate
the potential of liposomes as drug deposits in multilayered films
for surface-mediated drug delivery
Assembly of Poly(dopamine)/Poly(<i>N</i>‑isopropylacrylamide) Mixed Films and Their Temperature-Dependent Interaction with Proteins, Liposomes, and Cells
Many biomedical applications benefit
from responsive polymer coatings.
The properties of poly(dopamine) (PDA) films can be affected by codepositing
dopamine (DA) with the temperature-responsive polymer poly(<i>N</i>-isopropylacrylamide) (pNiPAAm). We characterize the film
assembly at 24 and 39 °C using DA and aminated or carboxylated
pNiPAAm by a quartz crystal microbalance with dissipation monitoring
(QCM-D), X-ray photoelectron spectroscopy, UV–vis, ellipsometry,
and atomic force microscopy. It was found that pNiPAAm with both types
of end groups are incorporated into the films. We then identified
a temperature-dependent adsorption behavior of proteins and liposomes
to these PDA and pNiPAAm containing coatings by QCM-D and optical
microscopy. Finally, a difference in myoblast cell response was found
when these cells were allowed to adhere to these coatings. Taken together,
these fundamental findings considerably broaden the potential biomedical
applications of PDA films due to the added temperature responsiveness