Newly developed, bioinspired cell delivery vehicles

Date:
August 6, 2021
Source:
University of Mu"nster
Summary:
A research team has designed nanocontainers made of sugar and
protein components. These containers are taken up by cells through
natural processes and can thereby transport substances that normally
cannot penetrate the cell membrane -- such as drugs or labelled
substances for the investigation of cell functions -- into cells.



FULL STORY ========================================================================== Nanocontainers can transport substances into cells where they can
then take effect. This is the method used in, for example, the mRNA
vaccines currently being employed against Covid-19 as well as certain
cancer drugs. In research, similar transporters can also be used to
deliver labelled substances into cells in order to study basic cellular functions. To take advantage of their full potential, scientists are
conducting intensive research into how nanocontainers interact with
biological environments and how they have to be chemically constructed
to deliver cargo into cells in the gentlest and most controllable way
possible.


========================================================================== Scientists at the University of Mu"nster have recently developed a new
type of nanocontainer that is constructed entirely from biological
components. Unlike other cargo transporters, these are not based on
lipids but on sugar compounds which are sealed with a shell of protein structures -- so-called polypeptides - - the thickness of which is
precisely tailored. "We do produce the components of our nanocontainers synthetically, but they are taken up by cells and -- due to the overall structure we have developed -- also degraded by them just like naturally occurring substances," explains chemist Prof Bart Jan Ravoo. "For
the degradation of the container shell inside the cell, we make use
of two naturally occurring mechanisms -- as a result, the transported substances are released rapidly, as soon as they arrive in the cell,"
adds biochemist Prof Volker Gerke.

The scientists want to use the tiny nanocontainers, which are about
150 nanometers in diameter, to load cells with labelled biologically
relevant lipids that can be used to study transport processes occurring
within the cell membrane. In addition, they plan to further develop
the chemical design of the containers in such a way that they are, for
example, only taken up by certain types of cells or only release their
cargo when stimulated by external light.

In the future, transport systems built from sugar and protein components
might also be suitable for applications in living organisms to deliver
drugs specifically into certain tissues and cells. The study was published
in the journal Advanced Science.

Bioinspired materials organize themselves, forming cargo-carrying
containers To synthesize the new cargo transporters, the scientists
used sugar compounds (modified cyclodextrins) that are similar in
structure -- and thus behaviour - - to certain lipids naturally found
in every cell. Similar to the protective cell membrane lipids, the sugar structures arrange themselves, forming a shell in which they enclose the substances to be transported. However, because the resulting container
is still leaky and would lose its cargo over time, the scientists added
protein structures (polypeptides) that form a sealing layer around
the container. "To test how thick the sealing layer needed to be, we
varied the length of the peptide sequences and tailored them so that
the containers stably encapsulated their cargo," explains Sharafudheen
Pottanam Chali, a chemistry doctoral student and one of the study's two
lead authors.

Nanocontainers that use a natural pathway into cells In the next
step, the scientists investigated whether and how the newly developed nanocontainers were taken up by cells. Their hypothesis was that this
happens via so-called endocytosis. In this process, the cells internalize
a part of their cell membrane and pinch it off, creating small vesicles
called endosomes in which extracellular material is transported into
the cell. To test this, the scientists used a sugar compound (dextran)
known to be taken up by endocytosis. They treated their cell cultures
with red fluorescent dextran and, at the same time, added nanocontainers
filled with a green fluorescent cargo (pyranine). "In the fluorescence microscope, it became visible that both substances were taken up into the
cells equally and their fluorescence overlapped visibly -- therefore
we could conclude that the nanocontainers, just like the dextran,
were efficiently taken up by the cells through the endosomal transport process," explains Sergej Kudruk, a biochemistry doctoral student and
also a lead author of the study. The scientists confirmed this for two different cell types -- human blood vessel cells and cancer cells.

Container shell is degraded by enzymes in the cells' endosomes Conditions inside the endosomes differ from those of the cellular environment,
something which the scientists already were considering when designing
their nanocontainers. They constructed the containers in such a way that
the altered environment in the endosomes destabilizes and partially
degrades the polypeptide shell -- the nanocontainers thus become
leaky and release their cargo into the inside of the cell. "When the
containers are taken up into endosomes, two types of enzymes, which
we knew to be present in endosomes and which can contribute to the
degradation of the shell at specific sites, come into play," explains
Sergej Kudruk. "So-called reductases degrade the disulfide bridges that
were previously established to crosslink the peptide molecules of our nanocontainers -- in addition, peptidases cleave the peptide molecules themselves," adds Sharafudheen Pottanam Chali. The scientists also tested
the degradability of the container shell outside the cell. To do so,
they loaded the containers with a fluorescent dye and simulated part of
the complex endosomal microenvironment by using the enzyme trypsin as
well as reducing agents. After treatment, the dye leaked out immediately.

========================================================================== Story Source: Materials provided by University_of_Mu"nster. Note:
Content may be edited for style and length.


========================================================================== Journal Reference:
1. Sergej Kudruk, Sharafudheen Pottanam Chali, Anna Livia Linard
Matos, Cole
Bourque, Clara Dunker, Christos Gatsogiannis, Bart Jan
Ravoo, Volker Gerke. Biodegradable and Dual‐Responsive
Polypeptide‐Shelled Cyclodextrin‐Containers for
Intracellular Delivery of Membrane‐Impermeable Cargo. Advanced
Science, 2021; 2100694 DOI: 10.1002/advs.202100694 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2021/08/210806104322.htm

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