Nanomaterials: Evolution and Advancement Towards Therapeutic Drug Delivery (Part I)

With every era, medical science faces challenges to provide the best health care and efficient drug therapy for the treatment of existing diseases. Current regimes of chemical drugs, though beneficial in a certain sector, have several disadvantages; cytotoxicity and adverse health effects are of primary concern. To accomplish efficient as well as the safe mode of transport for drugs and bioactive molecules, nanotechnology has provided an answer in terms of nanomedicines. Polymeric nanoparticles that can easily be modified to suit the needs not only act as a vehicle to efficiently deliver the drug to the target site but also enhance the bioavailability of the drug. Polymer-drug conjugation delivers the drug specifically to the targeted tumors. The conjugation facilitates increased retention time and enhanced cellular permeability that enables better suppression of the tumors. This chapter gives an insight into the properties of nanoparticles, highlighting the associated advantages and limitations of polymeric nanoparticles as a vehicle of drug delivery to cells.

Characterization of nanostructured systems is an important aspect to support the choice of the better formulation composition and the best production conditions throughout a development process. Several methods can be used alone or combined for the determination of physical (e.g., mechanical, electrical, electronic, magnetic, thermal and optical), chemical or biological properties of a nanomaterial. This chapter is an overview of the most employed techniques, including dynamic light scattering and laser diffraction for the determination of size distribution; zeta potential and its relationship with stability and the surface charge of the particles; microscopies (optical microscopy, SEM, TEM, AFM) utilized in morphological analyses; spectroscopies in the infrared or ultraviolet-visible regions, and X-rays diffraction, which help to elucidate the crystalline state, polymorphism and drug-nanosystem interaction; and thermal analyses, which can provide information about the physical state, crystallinity, and stability. Further complementary information can be obtained from many other methods, such as nuclear magnetic resonance or Raman spectroscopy, but they are beyond the scope of this chapter. The careful choice of the characterization techniques to be used is certainly a decisive step in the successful and rational development of a nanocarrier formulation.

Liposomes are spherical vesicular systems composed of lipid bilayers. Among the various novel drug delivery systems, it has been found that the liposomes follow an advanced technology for the delivery of drugs to the target site. In the present era, there are various liposomal formulations which are in clinical use. Due to the extensive efforts of the researchers, there has been tremendous progress in liposomal technology, i.e., from, conventional vesicles to the 2nd generation liposomes. The current review article deals with the materials involved in the preparation of liposomes, techniques for preparation, characterization studies and application of liposomes for drug delivery.

In the recent past, dendrimer based nano-devices have become an attractive center for medicinal chemists as a targeted drug delivery carrier. It is promising to specifically manipulate both molecular weight and chemical composition of dendrimers by regulating dendrimer synthesis, and thereby allowing predictable tuning of their biocompatibility and pharmacokinetics. The myriad properties and functions of dendrimers provide plenty of opportunities in this regard. Presently, the fields of oncology, infectious disease, cardiovascular diseases, ocular disease, etc. need biodegradable polymers, macromolecules based formulations to improve the safety and efficacy of different therapeutics. Dendrimer has been extensively used for treating disorders even for anti-viral therapeutics, including AIDS-HIV . The present book chapter reports the role of dendrimers in drug delivery systems for various agents, in biology and medical science. Additionally, it covers the fundamentals of dendrimeric properties and types for cancer diagnosis and other therapy.

Currently, nanomicelles are used pharmaceutically for solubilizing hydrophobic drugs, improving bioavailability, targeting anticancer drugs, and many more applications are associated with the use of nanomicelles. By definition, nanomicelles are colloidal dispersions containing a hydrophobic core and a hydrophilic shell that self-assemble itself into the nanosize range of 10-100 nm. The major limiting factor for formulating a clear aqueous solution of a drug is its hydrophobic nature. Nanomicelles improve the solubilization of hydrophobic drugs by entrapping the drugs within a mixed micellar hydrophobic core with hydrophilic chains protruding outwards, forming a clear aqueous formulation. Pharmaceutically nanomicelles serve as outstanding carriers as they can avert or moderate drug degradation by dropping adverse side-effects, thereby augmenting drug permeation through biological barriers with very minimum or no irritation at all, which ultimately enhance bioavailability. The major factors that affect the micelle formation are the hydrophobic part size in the amphiphilic molecule, amphiphiles concentration, temperature and solvent. The assembling process starts only when a certain minimum concentration is crossed by the amphiphilic molecules, called Critical Micelle Concentration (CMC). Therefore, in this chapter, a critical history of nanomicelles is provided from its fundamental theory to preclinical and clinical achievements.

For almost the last three decades, carbon nanotubes (CNTs) are under continuous scientific investigation due to the inimitable properties and immense applications in diverse fields, especially in drug delivery. CNTs are the rolled graphene sheets with sp2 hybridization. Various synthetic approaches like arc discharge method, laser ablation methods, chemical vapor deposition, and pyrolysis are employed to produce CNTs. Despite applications in biomedical sensors, artificial implants, preservatives, solar cells, and transistors, CNTs have also been explored to deliver anticancer agents, anti-malarials, anti-HIV agents, and anti-bacterial drugs. CNTs can even deliver nucleic acids and genes into cells of the target site. The present chapter explains the discovery of CNTs, their types, synthetic methods, various reactions possible with the usage of CNTs, applications of CNTs, safety profile, and challenges involved.

Magnetic nanoparticles have attracted tremendous attention in drug delivery and other biomedical applications since the last two decades. Many magnetic nanoparticle based formulations are already available in the market and even many more are under different stages of development. The incredible progress in this area is due to well-established synthesis procedures of size and shape-controlled magnetic nanoparticles as well as their well-recognized surface functionalization approaches. Advanced drug delivery systems consider the shape, colloidal stability, density of surface anchoring groups on nanoparticle surface as well as responsive and sustained release of drug molecules along with integrated imaging modality.