uptake; (3) improved bioavailability via delivery of the drug at the site of action at
reduced dosage, enabling sustained and controlled release; (4) enhanced
biodistribution with reduced toxicity and minimal nonspecific interactions with
the host; and ultimately (5) reduced patient expenses and non-compliance by
evading repeated administration [10, 11]. In a nutshell, nanoencapsulation of
drugs within biodegradable polymers provides enhanced drug efficacy, specificity,
tolerability, and a better therapeutic index [12]. The essential hallmarks of the
selected drug carrier for attaining these desired outcomes are listed below.
1.1 Loading Capacity
The extent of drug carried by/within a drug carrier is expressed by its loading
capacity. Drug loading is denoted by two terms: “entrapment efficiency”, which is
the drug loaded in a carrier as a fraction of the total drug used in the loading process
and “loading efficiency”, which is a measure of the amount of drug loaded into a
unit value of the drug carrier used, usually expressed as drug-to-polymer ratio.
Entrapment and loading efficiencies may vary depending upon the nature of the
drug and the method of loading. The higher the loading, the better the clinical
therapeutic outcome conferred at low doses.
1.2 Release Characteristics
Delivery of the loaded contents from a drug carrier may occur either via degradation
of the drug carrier or by slow diffusion of the drug through the carrier matrix, and is
expressed as the release rate. The method of drug incorporation within the
nanomatrix influences the release profile considerably. For drugs incorporated
within the matrix during its preparation, a relatively small burst effect with better
sustained release characteristics is obtained. For nanoparticles stabilized with a
polymer coating, release is controlled by diffusion of the drug from the core across
the polymeric membrane. Ionic interactions between the drug molecules as well as
the addition of surfactant molecules can also drastically affect the release rate. Thus,
drug solubility, diffusion, and biodegradation of the matrix materials govern the
release process. A slow and sustained release rate at the tissue/organ of therapeutic
action will enable improved bioavailability and, thereby, clinical outcomes.
1.3 Stability
One of the main concerns in nanoparticle engineering is to maintain the stability of
the primary particles because otherwise the advantages of the small particle size are
Proteins and Carbohydrates as Polymeric Nanodrug Delivery Systems. . .
243
reduced dosage, enabling sustained and controlled release; (4) enhanced
biodistribution with reduced toxicity and minimal nonspecific interactions with
the host; and ultimately (5) reduced patient expenses and non-compliance by
evading repeated administration [10, 11]. In a nutshell, nanoencapsulation of
drugs within biodegradable polymers provides enhanced drug efficacy, specificity,
tolerability, and a better therapeutic index [12]. The essential hallmarks of the
selected drug carrier for attaining these desired outcomes are listed below.
1.1 Loading Capacity
The extent of drug carried by/within a drug carrier is expressed by its loading
capacity. Drug loading is denoted by two terms: “entrapment efficiency”, which is
the drug loaded in a carrier as a fraction of the total drug used in the loading process
and “loading efficiency”, which is a measure of the amount of drug loaded into a
unit value of the drug carrier used, usually expressed as drug-to-polymer ratio.
Entrapment and loading efficiencies may vary depending upon the nature of the
drug and the method of loading. The higher the loading, the better the clinical
therapeutic outcome conferred at low doses.
1.2 Release Characteristics
Delivery of the loaded contents from a drug carrier may occur either via degradation
of the drug carrier or by slow diffusion of the drug through the carrier matrix, and is
expressed as the release rate. The method of drug incorporation within the
nanomatrix influences the release profile considerably. For drugs incorporated
within the matrix during its preparation, a relatively small burst effect with better
sustained release characteristics is obtained. For nanoparticles stabilized with a
polymer coating, release is controlled by diffusion of the drug from the core across
the polymeric membrane. Ionic interactions between the drug molecules as well as
the addition of surfactant molecules can also drastically affect the release rate. Thus,
drug solubility, diffusion, and biodegradation of the matrix materials govern the
release process. A slow and sustained release rate at the tissue/organ of therapeutic
action will enable improved bioavailability and, thereby, clinical outcomes.
1.3 Stability
One of the main concerns in nanoparticle engineering is to maintain the stability of
the primary particles because otherwise the advantages of the small particle size are
Proteins and Carbohydrates as Polymeric Nanodrug Delivery Systems. . .
243