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Файл:Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_5615_Библиотеки_им_академика_М_И_Перельмана.pdf
7 PEGylated Nanocarrier asaPromising Tool forSite-Specic Delivery ofTherapeutics
197
NGO Nanosized graphene oxide
NIR Near-infrared
NPs Nanoparticles
NSAIDs Nonsteroidal anti-inammatory drugs
NSCLC Non-small-cell lung carcinoma
OA Osteoarthritis
OPSS-PEG-ProG Orthopyridyldisulde-polyethylene glycol-succinimidyl
valerate
PAMAM Polyamidoamine
PCL Polycaprolactone
PDCs Polymer-drug conjugates
PdNP Palladium nanoparticle
PDT Photodynamic therapy
PEG Poly-ethylene glycol
PEGMnCaP Pegylated Mn2+-doped calcium phosphate
PEI Polyethyleneimine
PGA Polyglycolic acid
PIC Polyion complex
PLA Polylactic acid
PLGA Poly(lactic-co-glycolic acid)
POEGMEMA Poly(oligo(ethylene glycol) methyl ether methacrylate)
PPI Polypropyleneimine
ProA Protein-A
ProG Protein-G
PTT Photothermal therapy
PTX Paclitaxel
QDs Quantum dots
RES Reticulo-endothelial system
RGD Arginyl-glycyl-aspartic acid-peptide
RME Receptor-mediated endocytosis
Sct Salmon calcitonin
SiRNA Small interfering RNA
SPIONs Superparamagnetic iron oxide nanoparticles
SWNTs Single-walled carbon nanotubes
Tf Transferrin
VEGF Vascular endothelial growth factor
7.1 Introduction
The use of nanocarrier systems has been widely explored for the past few years
for the delivery of drugs as well as for diagnostic purposes. Also, it is advancing
from academic research to the eld of commercial success and clinical use. The
general availability of several nano-drug delivery systems serves as evidence of
this. When it comes to treating chronic human diseases, nanotechnology has many
advantages because of the targeted and site-specic transportation of highly
198
S. Acharya et al.
efcient medications. These systems have been shown to connect the dots between
biological and physical sciences (Patra etal. 2018). These systems are used for the
delivery of an extensive array of compounds, such as chemotherapeutics, biological
molecules, nucleic acids, enzymes, and peptides for the treatment of various diseases and disorders. With their application, severe side effects associated with anticancer drugs such as multiple organ failure, thrombocytopenia, and anemia can be
avoided along with better target specicity and dose reduction. They are capable of
passing across the smallest channels and biological barriers such as cell membranes,
which are crucial for the transport of medications to intracellular areas of action, as
well as epithelial and endothelial barriers and they are also capable of evading the
phagocytes (Vllasaliu etal. 2014).
Because of their small size, usually in nanometers, they can remain in the bloodstream for a longer time. Additional signicant benets for drug delivery can be
obtained by modifying the carrier’s properties, including targeted delivery, regulated or stimuli-responsive distribution, and shielding of the drug from biological
milieus. They have the capability to control the release of loaded drugs, due to their
unique capability to biodegrade, heat sensitivity of structural elements, and pH,
making them suitable for the administration of drugs or molecules (Farjadian etal.
2019). The following section expounds on their advantages over conventional drug
systems.
7.2 Drawbacks ofConventional Drug Delivery Systems
One of the biggest challenges in the management and treatment of diseases is getting the effective drug to the desired spot. Major drawbacks of conventional drug
delivery systems such as through the oral, buccal, sublingual, rectal, and subcutaneous routes are poor selectivity, insufcient bio-distribution, off-target effect, large
molecular size, inability to cross the biological membranes, damage to healthy cells,
and limited efcacy. Some physiological barriers of the body also hinder drug activity such as the blood-brain barrier by restricting the entry of the active component
(Wilczewska etal. 2012). The majority of conventional systems have a large rst
explosion of drug release that occurs right after drug administration, and they also
have a low tendency for drug solubility. Also, there is difculty in eliminating the
remnants of such systems, which can lead to the patient’s body containing hazardous non-biodegradable substances. Targeted drug delivery systems can help to overcome the aforementioned limitations. The drug is carried to the site of action in
controlled drug delivery systems, minimizing its impact on sensitive tissues and
unfavorable side effects, especially in cancer treatment and brain-associated disorders. Additionally, they increase drug concentration in target tissues and shield them
from quick oxidation or removal, thus reducing the dosage of the drug (Farjadian
etal. 2019).
7 PEGylated Nanocarrier asaPromising Tool forSite-Specic Delivery ofTherapeutics
199
7.3 Nanocarrier-Based Targeted Drug Delivery
The elds of nanotechnology and nanomedicine have undergone a revolution as the
number of nano-based medicinal compounds has increased dramatically since 1980.
These innovative nano-based materials can either function as therapeutic agents or
can be utilized to deliver active components to specic cells or tissues, with
increased bioavailability as well as target specicity, ability to cross biological
membranes, and prolong drug release. They can also escape endothelium at inammatory regions, epithelium, malignancies, or micro-capillaries simply due to their
small stature. Therapeutic compounds can be shielded from enzymatic breakdown
by nucleases and proteases using an adaptation of this procedure. Numerous studies
have shown that using nanoparticles (NPs) as a medication, delivery strategy has an
array of benets over conventional methods. The creation of nanoparticles using
biodegradable materials enables prolonged drug release at the target site over days
or even weeks (Singh and Lillard 2009).
These systems are used to enhance efcacy and reduce undesired side effects.
The commonly marketed targeted nanocarrier system includes nanocrystals, lipid
nanoparticles, PEGylated polymeric nanocarriers, nanobers, quantum dots (QDs),
liposomes, dendrimers, micelles, protein-based nanoparticles, and metal-based
nanoparticles. The eld of nanomedicine heavily relies on PEGylated nanocarriers
(Vllasaliu etal. 2014). It has been widely known that PEGylation presents enormous potential for enhancing the efcacy of nanomedicines. This chapter will take
a look at some of the PEGylated nanomedicines that are currently being investigated and highlight the benets of PEGylation for drug delivery.
7.4 Methods ofPEGylation
There are two approaches by which PEGylation can be achieved. Figure7.1 is a
schematic representation of the methods of PEGylation.
7.4.1 Covalent Approach
One of the methods for stabilizing proteins is PEG conjugation (PEGylation), which
is commonly referred to as the covalent approach. Polyethylene glycol (PEG) is a
hydrophilic, un-ionized, and safe polymer that offers proteins a steric barrier,
improving the proteins’ pharmacological properties. PEGylation also shields proteins invitro from protease digestion and aggregation. However, covalent PEGylation
necessitates a time-consuming and expensive chemical reaction to conjugate PEG
to proteins (Kurinomaru and Shiraki 2015).
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S. Acharya et al.
Fig. 7.1 Various methods of PEGylation
7.4.2 Non-covalent Approach
A novel technique called non-covalent PEGylation avoids a chemical reaction
between the PEG and the protein. It is based on the mechanisms of ionic interactions, protein polyelectrolyte complexes, hydrophobic interactions, or chelation.
The main benet of this method is that it prevents product loss that could result from
additional purication procedures. However, a signicant drawback of this strategy
is that the protein is leached while being stored (Belén etal. 2019).
Protein stabilization using non-covalent PEGylation, also referred to as supramolecular PEGylation, has been proposed as an alternative technique. For noncovalent PEGylation, functional PEG derivatives that bind to proteins are frequently
designed. Many PEG derivatives were conjugated with hydrophobic ligands, which
prevented salmon calcitonin and lysozyme from aggregating. PEG derivatives have
also been created that are conjugated with sugars, biotin, and nitrilotriacetic acid
(Kurinomaru and Shiraki 2015; Andrianov 2023). Additionally, because of the
7 PEGylated Nanocarrier asaPromising Tool forSite-Specic Delivery ofTherapeutics
Fig. 7.2 Representation of Cucurbiturils (CB[n]) mediated protein PEGylation utilizing guest
moieties such as viologen and naphthalene-modied components
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transitory nature of the PEG chain’s bond with the protein, non-covalent PEGylation
has been proposed to lower the danger of an immune response and facilitate straightforward approval by health authorities. The idea of supramolecular PEGylation
goes beyond shielding proteins with ensuing drug release, much like releasable
covalent PEGylation or other tunable drug release carriers. It stems from a defense
mechanism, that involves dynamic protein modication mediated by different hostguest or polyelectrolyte exchange reactions. PEGylation that is non-covalent avoids
site-specic attachment, enabling effective pharmacokinetic modulation using
monovalent and multivalent strategies (Andrianov 2023).
7.4.2.1 PEGylation Via Monovalent Interactions
The idea of functionalized PEG being attached to a protein surface at a single point
is similar to how traditional PEGylation technology operates. As listed below, these
are divided into different approaches.
High-Affinity Host-Guest Interactions
This method only works with proteins that have N-terminal aromatic residues, or
the protein would need to be chemically altered. The protein surface must be treated
with a small molecule recognition moiety in the latter scenario, but reactions involving end-functionalized PEG macromolecules will still be required. It is also common to refer to PEGylation involving host-guest interaction as “reversible” or
“dynamic” PEGylation, implying the release of protein under specic circumstances in the absence of lysis of covalent bonds. The host-guest complexes that
cause PEG-protein binding can be compared to supramolecular “handcuffs” that
bind the components together as shown in Fig.7.2.
Hydrophobic Association, Ionic, andCoordinate Bonds
Hen egg-white lysozyme (HEL) and salmon calcitonin (sCT) are two of several
examples of proteins that have been stabilized against aggregation using
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Fig. 7.3 PEGs with
functionalized structures
that have a range of end
groups that can interact
with proteins
non-covalently
S. Acharya et al.
mono- functionalized PEGs that contain benzyl-, phenyl butylamino-, cholesteryl-, dansyl-, and -tryptophan. Some of the PEG functionalized derivatives are
shown below in Fig.7.3.
A unied site ionic bond or hydrophobic association drove the formation of complexes. The aggregation of sCT was lowered for up to 70h by both dansyl and
tryptophan derivatives. A benzyl-derivative of PEG caused some protein degradation, whereas cholesteryl functionalized PEG completely prevented HEL from
aggregating. According to reports, PEGs that have been functionalized with phenylbutylamino, tryptophan, and dansyl extended the lag phase of protein aggregation
and decreased its rate. Non-covalent PEGylation outperformed native protein by a
factor of 3–4 as regards in vivo half-life, solubility, and bioavailability
(Andrianov 2023).
7.4.2.2 PEGylation Via Multivalent Interactions
Macroions are exible and can locate oppositely charged surfaces on the protein—
charge anisotropy model of interactions. This characteristic as well as entropy
changes brought on by counterion release have both been shown to favor proteinpolyelectrolyte interactions. Certain multivalent interactions utilize the “bind and
slide” mechanism, where a counter-partner can switch between binding sites along
a polymer chain. It is conceivable that the latter will advance the development of
dynamic PEGylation, in which the protein’s active site is periodically made accessible to interact with its substrate molecule without chemical cleavage of the protein
complex.
7 PEGylated Nanocarrier asaPromising Tool forSite-Specic Delivery ofTherapeutics
Fig. 7.4 (a) PEGylated block copolymers. (b) PEGylated graft copolymers
203
PEGylated Block Copolymers
Two or more distinct polymer chains joined by covalent bonds typically make up
block copolymers as shown in Fig.7.4 below. They can be effortlessly customized
by mixing biodegradable polymers like polylactic acid (PLA), polyglycolic acid
(PGA), poloxamers, polycaprolactone (PCL), poly (lactic-co-glycolic acid)
(PLGA), and poly(ethylene glycol) (PEG). Block copolymers endowed with customized characteristics, chemical compositions, and molecular weights (MW) are
now much easier to design, thanks to recent improvements in synthetic methods and
thus been, widely used in the creation of nanomaterials to improve drug efcacy,
decrease drug toxicity, and provide long-term therapeutic options. Other applications include precise programming of the drug release prole and surface modication with targeting ligands. Drug delivery is not the only application for block
copolymers; they can also be used for tissue engineering, medical devices, and
wound dressing (Agrahari and Agrahari 2018). The main distinction between a
block copolymer and a graft copolymer is that the former has blocks of repeating
units while the latter has branches of repeating units.
PEGylated Graft Copolymers
Graft copolymers are made up of a main polymer chain called the backbone, to
which one or more polymer sidechains are covalently joined, creating the branches
as shown in Fig.7.4. Typically, the branches’ and backbone’s chemical nature and
composition are different (Sadeghi and Sayaf 2014; Madhu 2018). The complexation of two graft copolymers of Dextran Sulfate and PEGylated Pentosan
Polysulfate with Keratinocyte Growth Factor-2 was used to investigate the role of
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Fig. 7.5 Schematic representation of the combination of the angiogenesis inhibitor Sprouty1
(Spry1) with poly(oligo (ethylene glycol) methyl ether methacrylate) modied with maleimide
(MI-POEGMEMA) and bovine serum albumin (BSA) to create complex micelles (Spry1)
S. Acharya et al.
macromolecular architecture. An increase in the protein’s melting temperature
revealed that protein binding was decreased by both polymers’ ability to stabilize
the protein.
PEGylated Proteins asMacro-reagents
PEGylated macro reagents are reagents that contain polyethylene glycol (PEG)
chains attached to large molecules or structures, such as proteins, antibodies, liposomes, or nanoparticles. Protein-protein interactions as a basis for non-covalent
PEGylation were also investigated. Covalent attachment of negatively charged
bovine serum albumin (BSA) with poly(oligo(ethylene glycol) methyl ether methacrylate), POEGMEMA results in a “macro-reagent.” This was tested for its ability
to bind lysozyme and Sprouty 1 (Spry1), two positively charged proteins as shown
in Fig.7.5 below. The IC50 value of Sprouty 1 was assessed against breast cancer
cells and was found to be decreased as a result of this “protein-protein”-mediated
modication. The complex’s high anticancer effectiveness was also demonstrated
by its ability to restrain the development of 3D MCF-7 multicellular tumor spheroids. While PEGylated protein mediator technology has some benets like lowering
the design complexity, it nevertheless requires the mediating protein to be covalently modied. The range of suitable interacting proteins is also restricted.
Pairs ofComplementary PEGylated Macroions
Polyelectrolyte Complex-Based Systems
Proteins can be coassembled with two PEGylated polyions that have opposing
charges. This may have the benet of increasing the environmental stability of polyelectrolyte complexes and multilayer coatings. The pathway typically starts with the
complexation of the protein with the rst polyion and is followed by the addition of
an oppositely charged second polyelectrolyte. A pair of interacting non-ionic macromolecules may also be used to create a ternary polymer-protein-polymer
7 PEGylated Nanocarrier asaPromising Tool forSite-Specic Delivery ofTherapeutics
Fig. 7.6 Counterion release after polyion self-assembly into PIC nanoparticles is depicted
(charged spheres). In this instance, too much polycation in the mixture causes a neutral core to
form, which is encircled by too much cationic material. (Adapted with permission from Insua etal.
2016 under the terms of the Creative Commons CC-BY license (https://s100.copyright.com/AppD
ispatchServlet?publisherName=ELS&contentID=S0014305716301860&orderBeanReset=true)
© 2016 The Authors. Published by Elsevier Ltd)
205
assembly. In a solution, colloidal polyion complex (PIC) particles made of oppositely charged polyions can self-assemble as shown in Fig.7.6 below.
Non-ionic Interaction-Based Systems
The co-assembly of the insulin hormone into a three-component complex during a
dual-stage non-covalent process for PEGylation of insulin peptide was reported.
First, insulin was complexed with zinc-chelated poly(aspartic acid-co-
aspartglucosamine- co-aspartnitrilotriacetic acid) via the peptide’s histidine groups.
This was followed by the addition of a block copolymer of poly(ethylene glycol)-bpoly(aspartic acid-co-aspartamidophenylboronic acid) containing PEG.This produced PEG shell-stabilized submicron-sized (122–187 nm diameter) micelles
(Andrianov 2023).
PEGylated Dendritic Copolymers
The fundamental structure of telodendrimers is a diblock copolymer AB made up of
a linear polymer (A) like PEG, a poly(ester), or a poly(amide); and a hyperbranched
dendron like PAMAM-, polyester-, and polyamine (B). A schematic representation
of telodendrimer is shown in Fig.7.7. Most examples of telodendrimers that have
been published are made of a hydrophilic linear polymer, like PEG, coupled with
dendrons, like poly(lysine) or poly(ester), functionalized with hydrophobic moieties. Dendritic copolymers were utilized as yet another fascinating application of
PEGylation that is completely dependent on non-covalent interactions. To create
telodendrimers composed of a series of 11 copolymers, different combinations of
charged functionalities were combined, including hydrophobic functionalities like
heptadecanoic acid, cholesterol, and tocopherol, cationic functionalities like arginine and lysine, and anionic functionalities like oxalic acid.
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S. Acharya et al.
Fig. 7.7 Typical representation of a telodendrimer
Utilizing isothermal titration calorimetry, electrophoresis, bio-layer interferometry, Forster resonance energy transfer spectroscopy, and other computational techniques, their interactions with proteins were investigated. The resultant nanoparticles
loaded with protein were about 30nm in size and effectively penetrated the cells.
Furthermore, the enhanced permeability and retention (EPR) effect and enhanced
peptide retention in an orthotopic brain tumor allowed the non-covalently bound
nano-assemblies to effectively deliver proteins to xenografted tumors.
Telodendrimers’ dual multivalent ionic and hydrophobic functionalities have additive effects on protein binding afnity. Additionally, their hydrophobic groups stabilize protein binding in aqueous solutions by acting as annealing moieties
(Andrianov 2023).
PEGylated Copolymers Utilizing Mobile Side Groups
Mobile side groups on PEGylated copolymers result in exible and dynamic side
chains on the polymer backbone. These side groups can interact with each other or
with the environment, creating different shapes and structures of the copolymers.
Polyrotaxane structural design, featuring cationic moieties and PEG grafts, signicantly enhances polyelectrolyte-protein complexation (PEG-PRX). A diagrammatic
representation of the PEG-PRX is shown in Fig. 7.8. PEG-PRX outperforms