Biomedical Engineering Reference
In-Depth Information
the area of tissue regeneration, growth, and repair). For example, nanofiber scaffolds, generally used
to redevelop central nervous system cells and other organs, have been shown to facilitate the regen-
eration of axonal tissue in hamsters with severed optic tracts (Ellis-Behnke et al. 2006).
1.4.1.2 Drug Delivery Systems
Commercially available and conventional dosage forms for drugs generally suffer from many draw-
backs, such as the need for target specificity, a high rate of drug metabolism, cytotoxicity, high dose and
dosing frequency requirements, and poor patient compliance, among others. Nanotechnology has facili-
tated drug delivery systems by improving the physical, chemical, and biological properties that can pro-
vide efficient delivery means for currently available active pharmacological ingredients (APIs). Several
nanocarriers, such as polymeric NPs, polymeric micelles, liposome, niosomes, dendrimer, polymer-
drug conjugates, and antibody-drug conjugates, can generally be divided into the following categories:
1. Sustained and controlled delivery systems
2. Stimuli-sensitive/environment-sensitive delivery systems
3. Functionalized systems for the delivery of bioactives
4. Multifunctional systems for the combined delivery of therapeutics, biosensing, and
diagnostic
5. Site-specific, targeted drug delivery systems, including intracellular, cellular, and tissue
targeting (Vasir et al. 2005)
The direct, intravenous administration of APIs may induce toxicity due to first-order drug
release kinetics when compared to intravenous administration. In cases where a sustained release in
required, the field of NMs offers implantable delivery systems by virtue of their size, control, and
almost zero-order releases. Some novel vascular carriers, such as liposome, ethosome and transfero-
some, niosomes, and some implant chips, have been envisaged in recent times, which may assist in
the minimization of peak plasma levels with minimal adverse reactions, allow for longer and more
predictable action, decrease the frequency of dosing, and improve the levels of patient acceptance
and compliance.
Furthermore, various strategies are being developed for superior, site-specific delivery using
novel carriers such as polymeric NPs, liposomes, polymeric micelles, dendrimers, iron oxide, and
proteins, by modifying the active and passive uptake of drugs. The targeting of drugs to tumor
sites via passive delivery methods and using the improved permeation and retention (EPR) effect
is thought to be a unique strategy that uses this carrier system by taking advantage of the leaky
vasculature in tumors. Some surface modification techniques, using several targeted ligands via
covalent binding or adsorption to the carrier system, improved their site specificity, selectivity, and
formulation for active targeting. Carriers with targeted, ligand conjugations provide site specificity
at various levels. In tuberculosis chemotherapy, the active targeting to lung cells is accounted to
have enhanced drug bioavailability, a reduction in dosing frequency, and avoiding the nonadherence
trouble that was encountered in the control of tuberculosis.
1.4.1.3 Nasal Vaccination
The use of nanosphere carriers for the delivery of vaccine is currently under development. Nasal
vaccinations of antigen-coated, polystyrene nanospheres are widely used for targeting human
dendritic cells (Matsusaki et al. 2005). Nanospheres had a positive effect on human dendritic cells
by inducing the transcription of genes important for phagocytosis as well as an immune response.
1.4.1.4 Cancer Diagnosis and Treatment
NMs can have a great impact on cancer therapy and diagnoses. Current, commonly available cancer
treatments are surgery, chemotherapy, immunotherapy, and radiotherapy. NMs provide remarkable
opportunities to assist and improve available, conventional therapies, thereby allowing science to
