Parenteral Delivery of Peptides and Proteins - Challenges in Delivery of Therapeutic Genomics and Proteomics - page 548

1. Collagen: Collagen, due to its unique structural characteristics, has been fabricated into a
wide variety of forms including crosslinked films, meshes, fibers, and sponges. It offers sev-
eral advantages such as biocompatibility and nontoxicity in most tissues; ready isolation and
purification in large quantities; well-documented structural, physical, chemical, and immu-
nological properties; and the ability to be processed into a variety of forms. Limitations of
collagen include its poor dimensional stability due to swelling in vivo , poor in vivo mechan-
ical strength and low elasticity, possible occurrence of an antigenic response and tissue
irritation due to residual crosslinking agents, poor patient tolerance of ocular inserts, and
variability in drug release kinetics [154] .
2. Albumin: The exploitable features of albumin include its biodegradation into natural prod-
ucts, its ready availability, nontoxicity, and nonantigenicity.
3. Gelatin: Gelatin offers several advantages in drug delivery systems such as weaker binding
to drugs, less potential for drug degradation because of low preparation techniques, and
lower antigenicity [147] .
4. Polysaccharides: Polysaccharides or the polymers of monosaccharides have various natural
sources of origin, such as algal (e.g., alginate), plant (e.g., pectin, guar gum), microbial (e.g.,
dextran, xanthan gum), and animal (chitosan, chondroitin) [155] . Depending upon the surface
charge, polysaccharides can be divided into polyelectrolytes and nonpolyelectrolytes. The
former can be further divided into positively charged polysaccharides (chitosan) and nega-
tively charged polysaccharides (alginate, heparin, hyaluronic acid, pectin, etc.) [155,156] .
Due to the presence of various derivable groups on molecular chains, polysaccharides
can be easily modified both chemically and biochemically, resulting in many different
kinds of polysaccharide derivatives with diverse properties. Most of them possess hydro-
philic groups such as hydroxyl, carboxyl, and amino groups, which could form non-
covalent bonds with biological tissues (mainly epithelia and mucous membranes) and
confirming bioadhesion [157] . These bioadhesive polysaccharides have shown enhanced
drug loading, prolonged residence time in delivery system, with enhanced drug absorp-
tion and bioavailability [156] . These biodegradable agents have been used to prepare
microspheres and nanospheres [158] . In one study, albumin-loaded water-soluble chi-
tosan nanoparticles with various deacetylation degrees (DDs) and molecular weights
have been reported to promote loading efficiency and decrease the release rate [159] .
In another study, albumin-loaded quaternized cellulose nanoparticles were prepared as
a flexible potential carrier for sustained release of P/P [160] . Recombinant gelatin and
collagen are now available for drug delivery and tissue engineering applications and will
provide better control on quality, purity, and predictability of performance [161,162] .
11.5 Parenteral Delivery Systems for P/P
Several controlled release injectable particulate delivery systems have been investi-
gated for delivering a required therapeutic concentration of proteins and peptides to a
desired site in the body, at a desired rate, with minimal systemic exposure so as to pro-
tect the delivered proteins from the bioenvironment and to reduce unwanted side effects
at systemic circulation [20,163,164] . These systems include microspheres, implants,
liposomes, nanoparticles, vaccines adjuvants, and customized particulate systems
for pulsatile protein delivery [20,164] . These delivery systems have been a potential