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Файл:Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_5482_Библиотеки_им_академика_М_И_Перельмана.pdf
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Novel Drug Delivery Systems
INTRODUCTION
Novel drug delivery systems (NDDS) are innovative approaches
and technologies designed to improve the delivery of drugs to
their target sites in the body. Traditional drug delivery methods
often face challenges such as poor bioavailability, limited
drug stability, and inadequate targeting to specific tissues or
cells. NDDS aim to overcome these limitations and enhance
therapeutic outcomes.
Advantages of Novel Drug Delivery Systems
Enhanced drug efficacy: NDDS can optimize drug release
profiles, ensuring the right amount of drug is delivered at the
desired rate and duration. This can improve the effectiveness
of the treatment and reduce the required dosage.
Targeted drug delivery: NDDS enable precise targeting
of drugs to specific tissues, cells, or organs, increasing
drug concentration at the site of action while minimizing
exposure to healthy tissues. This can enhance therapeutic
efficacy and reduce side effects.
Improved patient compliance: NDDS can offer convenient and
patient-friendly administration routes, such as transdermal
patches, inhalation systems, or oral controlled-release
formulations. These options can improve patient adherence
to treatment regimens.
Enhanced drug stability: Some NDDS, such as liposomes
or nanoparticles, can protect drugs from degradation,
enhancing their stability and extending their shelf life.
Introduction to Pharmaceutics
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Controlled drug release: NDDS can provide controlled
and sustained release of drugs, maintaining therapeutic
drug levels over an extended period. This can reduce the
frequency of dosing and improve convenience for patients.
Limitations or Challenges
While novel drug delivery systems (NDDS) offer significant
advantages, they also have certain limitations that need to be
considered. Some of the limitations include:
Development challenges: Designing and developing NDDS
can be complex and time-consuming. It requires extensive
research, optimization, and validation to ensure safety,
efficacy, and scalability.
Cost: The development and production of NDDS can be
expensive due to the need for specialized equipment, mate-
rials, and manufacturing processes. This cost may influence
accessibility and affordability for patients.
Regulatory considerations: NDDS may require additional
regulatory scrutiny and approval compared to traditional
drug delivery systems. Meeting regulatory requirements
and demonstrating safety and efficacy can be a lengthy and
resource-intensive process.
Manufacturing scalability: Scaling up the production of
NDDS from laboratory to commercial scale can present
challenges. Ensuring consistent quality, reproducibility,
and stability of NDDS during large-scale manufacturing
can be technically demanding.
Stability and storage: Some NDDS, such as liposomes or
nanoparticles, may have limitations regarding stability and
storage conditions. They can be sensitive to temperature,
light, or other environmental factors, which may affect
their shelf life and efficacy.
Limited applicability: NDDS may not be suitable for all types
of drugs or therapeutic applications. Some drugs may not
be compatible with specific delivery systems, and certain
medical conditions or patient populations may not benefit
from the use of NDDS.
Safety concerns: Although NDDS aim to improve drug
delivery and minimize side effects, there may still be
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Novel Drug Delivery Systems
potential safety concerns associated with specific systems.
These concerns may include unexpected immune responses,
toxicity, or unintended interactions with the body.
Intellectual property protection: Developing and
commercializing NDDS may face challenges in protecting
intellectual property rights. The uniqueness and novelty
of the delivery system may be subject to imitation or
infringement, impacting potential returns on investment.
It is important to address these limitations through ongoing
research, development, and optimization of NDDS to maximize
their benefits and overcome challenges. Close collaboration
between researchers, pharmaceutical companies, regulatory
agencies, and healthcare professionals is crucial for realizing the
full potential of NDDS in improving drug delivery and patient
outcomes.
CLASSIFICATION OF NOVEL DRUG
DELIVERY SYSTEMS
Novel drug delivery systems (NDDS) can be classified into
various categories based on their mechanism of drug release,
route of administration, and formulation. Here are some
examples of NDDS in each category.
Lipid-based Delivery Systems
1. Liposomes (Fig. 7.1): Liposomes are spherical vesicles
composed of lipid bilayers that can be used as carriers for
drug delivery and other applications. They are similar in
structure to cell membranes, consisting of an aqueous core
enclosed by one or more lipid layers.
Fig. 7.1: Structure of liposomes
Introduction to Pharmaceutics
298
Some important features and characteristics of liposomes:
y Composition: Liposomes are primarily composed of
phospholipids, which are amphiphilic molecules
with a hydrophilic head and hydrophobic tails. The
phospholipids arrange themselves in bilayers, with the
hydrophilic heads facing the aqueous environment and
the hydrophobic tails forming the interior of the vesicle.
y Size and structure: Liposomes can vary in size, ranging
from tens to hundreds of nanometers in diameter. They
can exist as unilamellar liposomes with a single lipid
bilayer or as multilamellar liposomes with multiple
concentric lipid bilayers.
y Encapsulation: Liposomes have the ability to encapsulate
both hydrophilic and hydrophobic drugs within
their aqueous core or lipid bilayers, respectively. This
property allows for the delivery of a wide range of
drugs with varying solubilities.
y Drug delivery: Liposomes act as carriers to transport
drugs to specific target sites in the body. They can
protect encapsulated drugs from degradation, improve
their stability, control their release kinetics, and enhance
their therapeutic efficacy.
y Biocompatibility: Liposomes are biocompatible and
generally well-tolerated by the body. They are composed
of natural or synthetic lipids that are similar to those
found in cell membranes, reducing the risk of toxicity or
adverse reactions.
y Targeted delivery: Liposomes can be modified by incor-
porating targeting ligands, such as antibodies or
peptides, on their surface. This allows for targeted
delivery of drugs to specific cells or tissues, improving
drug accumulation at the desired site and reducing off-
target effects.
y Controlled release: Liposomes can be engineered to
achieve controlled and sustained release of drugs. The
release rate can be controlled by modifying the lipid
composition, adding lipids with specific properties,
or incorporating stimuli-responsive components that
respond to external triggers.
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Novel Drug Delivery Systems
y Applications: Liposomes have diverse applications
in the pharmaceutical field. They are used for drug
delivery, gene therapy, vaccine development, cosmetics,
and diagnostics. Liposomal formulations have been
developed for a variety of diseases, including cancer,
infectious diseases, and inflammatory conditions.
Liposomes offer advantages such as improved drug stability,
tar geted delivery, controlled release, and versatility in
formu lation. Ongoing research aims to optimize liposomal
formulations, develop new strategies for drug loading,
and enhance their therapeutic potential in various fields of
medicine.
2. Solid lipid nanoparticles (SLNs): Solid lipid nanoparticles
(SLNs) are submicron-sized colloidal particles composed of
solid lipids that are used as carriers for drug delivery systems
(Fig. 7.2). They have gained significant attention in
pharma ceutical research due to their unique properties and
potential applications.
Some characteristics feature of solid lipid nanoparticles are:
y Composition: SLNs are primarily composed of solid
lipids, such as triglycerides, fatty acids, and waxes.
Fig. 7.2: Structure of nanoparticles.
Introduction to Pharmaceutics
300
These lipids are biocompatible and biodegradable,
making SLNs suitable for drug delivery purposes.
y Particle size: SLNs have a particle size ranging from 10 to
1000 nanometers, making them submicron in size. The
small particle size allows for improved drug loading
capacity, stability, and enhanced drug release profiles.
y Stability: The solid lipid matrix in SLNs provides
physical stability to the nanoparticles and protects the
encapsulated drug from degradation. This stability
helps in preserving the therapeutic efficacy of the loaded
drug during storage and transportation.
y Drug loading: SLNs can encapsulate both hydrophobic
and hydrophilic drugs due to their lipophilic nature.
Hydrophobic drugs can be incorporated into the lipid
matrix, while hydrophilic drugs can be entrapped
within the aqueous phase or attached to the surface of
SLNs.
y Controlled drug release: SLNs offer controlled and
sustained drug release characteristics, which can be
crucial for maintaining therapeutic levels of drugs over
an extended period. The release rate can be modulated
by adjusting the lipid composition, particle size, and
surface modifications of SLNs.
y Biocompatibility and biodegradability: SLNs are composed
of biocompatible lipid materials, which minimize
the risk of toxicity or adverse effects. They are also
biodegradable, allowing for the gradual degradation of
the lipid matrix and elimination from the body.
y Targeted drug delivery: SLNs can be surface-modified
with ligands or antibodies to facilitate targeted drug
delivery. These surface modifications enable specific
interaction with target cells or tissues, enhancing drug
accumulation and therapeutic efficacy while minimizing
off-target effects.
y Versatile formulation: SLNs offer flexibility in formu-
lation, allowing for the incorporation of various
drugs, including poorly water-soluble drugs, peptides,
proteins, and genetic materials. They can also be
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Novel Drug Delivery Systems
formulated into different dosage forms such as creams,
gels, suspensions, or lyophilized powders.
3. Nanoemulsions: Nanoemulsions are colloidal systems
consisting of two immiscible liquids, typically oil and
water, stabilized by an emulsifier or surfactant. They
are characterized by extremely small droplet sizes in the
nanometer range, which provide unique properties and
potential applications.
The composition of nanoemulsions typically includes the
following components:
y Oil phase: The oil phase can consist of oils, lipids, or
hydrophobic active ingredients, depending on the
application. The choice of oil phase depends on factors
such as solubility, stability, and desired properties of the
nanoemulsion.
y Aqueous phase: The aqueous phase is usually water,
but it can also contain water-soluble components,
such as hydrophilic active ingredients, cosolvents, or
electrolytes.
y Emulsifiers/surfactants: Emulsifiers or surfactants play a
crucial role in stabilizing the nanoemulsion by reducing
interfacial tension between the oil and water phases.
They form a protective layer around the droplets,
preventing coalescence and maintaining the stability of
the nanoemulsion.
Methods of Preparation of Nanoemulsions
High-energy Methods
High-pressure homogenization: This method involves sub-
jecting the mixture of oil, water, and emulsifier to high
pressure, typically using a homogenizer or high-pressure
valve system. The high pressure disrupts the larger
droplets, resulting in the formation of smaller droplets and
the creation of a nanoemulsion.
Microfluidization: Microfluidization involves forcing the
mixture through a narrow channel under high pressure.
This process leads to intense shear forces that breakdown
larger droplets into nano-sized droplets.
Introduction to Pharmaceutics
302
Low-energy Methods
Phase inversion temperature (PIT) method: In this method, an
oil-in-water emulsion is initially prepared at a temperature
where the oil is the continuous phase. Then, the temperature
is increased to induce a phase inversion where the water
becomes the continuous phase, resulting in the formation
of nanoemulsion droplets.
Phase inversion composition (PIC) method: Similar to the PIT
method, the PIC method relies on changing the composition
of the emulsion to induce a phase inversion. By adjusting
the ratio of oil, water, and emulsifiers, a phase inversion
occurs, leading to the formation of nanoemulsion droplets.
Combination Methods
High-energy/low-energy combination: This method combines
high-energy techniques, such as high-pressure homogenization,
with low-energy techniques like PIT or PIC. The high-energy
step is used to reduce droplet size initially, followed by the low-
energy step to further refine and stabilize the nanoemulsion.
Polymeric Delivery Systems
1. Polymeric nanoparticles: Polymeric nanoparticles are
colloidal particles composed of polymers that have a size
range typically between 1 and 1000 nanometers. Polymeric
nanoparticles are particles made from synthetic or natural
polymers, such as poly(lactic-co-glycolic acid) (PLGA),
polyethylene glycol (PEG), chitosan, or polylactic acid
(PLA). Polymeric nanoparticles can be prepared using
various techniques, including nanoprecipitation, emulsion/
solvent evaporation, solvent displacement, and electrostatic
assembly. These methods allow for precise control over
particle size, drug loading, and surface properties.
Polymeric nanoparticles can encapsulate a wide range of
drugs, including hydrophobic and hydrophilic compounds.
The drug can be entrapped within the polymer matrix or
adsorbed onto the particle surface.
2. Hydrogels: Hydrogels are three-dimensional networks of
hydrophilic polymer chains that have the ability to absorb
and retain a large amount of water or biological fluids.
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Novel Drug Delivery Systems
They are soft and gel-like materials with properties similar
to natural tissues, making them suitable for a wide range of
biomedical applications.
Hydrogels are composed of crosslinked polymer chains
that can absorb and retain water or biological fluids. The
poly mer can be synthetic or natural, such as polyethylene
glycol (PEG), polyacrylamide (PAAm), polyvinyl alcohol
(PVA), or hyaluronic acid (HA).
Hydrogels have a high water content, typically ranging
from 90 to 99%. This high-water content gives them the
ability to swell and retain their structural integrity.
3. Microparticles: Microparticles are solid or liquid particles
made from biodegradable polymers, i.e. poly (lactic-
co-glycolic acid) (PLGA), poly(lactic acid) (PLA),
poly(caprolactone) (PCL), and chitosan. They are designed
to release drugs gradually over an extended period of
time, providing a controlled and sustained therapeutic
effect. Microparticles can be administered via various
routes, including oral, injectable, nasal, and topical routes,
depending on the specific application and desired drug
delivery profile.
Microneedle-based Delivery Systems
1. Microneedle patches: Microneedle patches are a novel
drug delivery system that consists of an array of tiny
needles, typically ranging from hundreds to thousands
of micrometers in length mainly used for transdermal
drug delivery. These microscopic needles are designed to
penetrate the outermost layer of the skin, known as the
stratum corneum, without reaching the nerve endings,
making the process painless.
2. Implantable delivery systems: Implantable delivery systems
are medical devices designed to deliver drugs or therapeutic
substances directly into the body through implantation.
These systems provide a controlled and sustained release
of the drug over an extended period, eliminating the need
for frequent dosing and ensuring a consistent therapeutic
effect.
Introduction to Pharmaceutics
304
3. Drug-eluting implants: Drug-eluting implants are medical
devices that are designed to deliver therapeutic drugs
directly to a specific site in the body. These implants are
typically made of biocompatible materials and are coated
or impregnated with drugs that are released gradually over
time. The purpose of drug-eluting implants is to provide
localized drug delivery, targeting the specific area where
the implant is placed, while minimizing systemic side
effects.
Examples of drug-eluting implants:
y Drug-eluting stents
y Drug-eluting orthopedic implants
y Drug-eluting intraocular devices
y Drug-eluting contraceptive implants
y Drug-eluting neurostimulation implants
4. Ocular inserts: Specialized devices designed to deliver
medi cations directly to the eye for the treatment of various
ocular conditions. They are small, thin, and usually
transparent or translucent in nature. Ocular inserts offer
advantages such as prolonged drug release, improved
bioavailability, reduced dosing frequency, and enhanced
patient compliance compared to conventional eye drops.
Types
y Solid ocular inserts
y Gel ocular inserts
y Ring ocular inserts
y Contact lens-based ocular inserts
Targeted Delivery Systems
1. Antibody-drug conjugates (ADCs): Antibody-drug conjugates
(ADCs) are a class of targeted cancer therapies that combine
the specificity of monoclonal antibodies with the cytotoxic
effects of chemotherapeutic drugs. ADCs are designed
to selectively deliver potent drugs to cancer cells while
minimizing damage to healthy cells, thereby increasing the
therapeutic index and reducing systemic toxicity.
2. Nanocarriers: Nanocarriers for targeted drug delivery
systems are specialized vehicles designed to deliver