growthUnpredictable gelation tendencyUnexpected dynamics of polymeric transitions.
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Nanocarbon tubes
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20 to 1000
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They are cylindrical molecules consisting of multilayers of rolled-up sheets of carbon atoms.
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High bioavailability because of its high specific surface area and nanosize range.Multiple conjugation sites for the drug molecule.
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Lack of solubility in aqueous media
|
|
Polymer-based nanoparticles
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10 to 1000
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Colloidal particles comprising drugs encapsulated or impinged by polymeric substance.
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Increase the stability of volatile drug substance Biodegradable, biocompatible, and non-immunogenic Site-specific targeted drug delivery Reduce the adverse drug reactions
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Toxic monomer aggregation Polymeric degradation On degradation, they yield toxic residual material
|
|
Polymer-based micelles
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10 to 100
|
Self-assembled nanoscopic core shell formed by amphiphilic copolymer, containing hydrophobic drugs surrounded by micelles and hydrophilic bioactive materials.
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Serves the advantage of controlled drug release NontoxicHigher physical stability Greater cargo capacity of drugs
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Poor drug loading efficiency.Poor in vivo stability Poor cellular interaction with malignant tissues
|
|
Dendrimers
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< 10
|
Branched molecules that consist of a core and spherical 3D morphology.
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Low toxic and antigenic.Biodegradable and metabolized.Can increase the half-life of the moiety.Good tissue permeability.Aids sustained and controlled drug release.
|
Limited storage condition.Time consuming.High material and equipment cost.Low retention.More complex in nature.
|
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Metallic nanoparticles
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< 100
|
They are nanosized metals that are synthesized and modified to bind along with ligands, antibodies, drugs, etc.
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Optical properties like photo absorption, light scattering, modified SERS (surface enhanced Raman scattering) and fluorescenceEnhance the resolutions of the imaging techniques such as MRI, tracking stem cells, and cellular molecules.
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They are concerned with the issues of high toxicity.Their shape, size, surface chemistry, targeting ligands, elasticity, and composition largely influence their toxic profile.High in material and production cost.
|
|
Quantum dots
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2 to 10
|
They are smaller nano range tiny nanoparticles and have good optical and electronic properties that vary from larger particles due to their intrinsic quantum mechanics.
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They are better than fluorophore dyes that are 20 times brighter.Variations in the wavelength ranging from 400 to 4000 nm range.They are economically cost effective and also amenable to high-speed printing techniques.
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Highly toxic and require stable polymer shell.The shells can alter the optical property.Hard to control the particle size of the nano structures.DegradationOverall conversion yield is poor.
|
|
Nanodiamonds
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~5
|
Medically used diamonds of size range lesser than 5 nm containing three main components: the core, surface, and the overall shape.
|
They can be used in the drug delivery in their original form whereas there is no need to apply the oxidation modification process due to their good aqueous solubility nature, without any acidic media treatment.Reduces adverse effects.High affinity towards proteins and antibodies forming stable conjugates
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Chances of genotoxicity occurrence due to the introduction of various chemical groups into the nanodiamonds.Difficulties in evaluation due to being smaller in size; special techniques such as radionuclide tracer are to be adopted.The process is quite complicated during the complexation of nanodiamonds with the active drug molecules covalently.Economically high in cost.
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3.3.1 Liposomes
They are vesicles of spherical shape that contain one or more bilayers of lipoidal structure self-assembled in aqueous media. They range from 50 to 100 nm in size. They have the ability to carry a wide range of composition matrixes and protect the biomolecules (Figure 3.3). They have the advantages of having higher entrapment efficiency of drug, biodegradability, and biocompatible property. They offer active and passive transfer of biomolecule delivery such as proteins and peptides functionalized with specific target ligands to enhance the bioavailability of the drug at a specific site or tissue [32]. For example, a group of researchers conducted a study alternative approach for intravitreal drug administration to treat diabetic retinopathy. They formulated a nanolipid carrier conjugated (NLC) with a repositioned drug (i.e., Itraconazole) surface coated uniformly with cationic polymer chitosan (CS) yielding a positively charged NLC providing prolonged time of ocular retention—interacting with the eye negatively charged mucosal layer. And it also reported an increase in NLC-drug permeation improving its bioavailability for ocular drug delivery system. Hence, the researchers concluded that CS coated Itraconazole NLCs are promising in the treatment of diabetic retinopathy [33].
Figure 3.3 Basic structure of liposomes.
3.3.2 Solid Lipid Nanoparticles (SLNs)
A globular structure containing a monolayer of phospholipid surrounds the dissolved or dispersed drug in the solid core. The employment of Solid Lipid Nanoparticles (SLN) as a drug delivery vehicle is being increasing day by day because it paves the way to an alternative suitable approach to the available traditional colloidal carrier mediated systems such as liposomes, polymer-based nanocarriers, and emulsions (Figure 3.4). Generally, SLN ranges from 50 to 1000 nm in size. They are constructed using a highly melting fatty matrix (solid lipid ingredients) to mask the challenges and limitations such as cytotoxicity, lipid and polymer degradation, drug leakage, nanoparticles agglomeration, high production cost, lack of large-scale manufacturing, and stability issues. SLN aims to formulate a biologically bio-compatible and protect the drug degradation and prolong the storage stability. Commonly they are formulated as a vehicle for delivering the therapeutic agent to the brain, cancerous tissues, for tubercular therapy, carriers for vaccines, topical application, and cosmetics [34].
Figure 3.4 Solid lipid nanoparticles (SLNs).
3.3.3 Nanocarbon Tubes
These are cylindrical structured molecules having a diameter of 0.3 to 3 nm and length of 20 to 1000 nm (Figure 3.5). Crystalline allotropic carbon sheets form mono- or multilayers of nanotubes. They take advantage by increasing the solubility and enhancing the cellular cytoplasmic and nuclei permeation, and they serve as a carrier for gene-based and protein-based drug delivery, while striking the thermal, electrical, and mechanical properties for the early-stage diagnosis of cancer in patients [35].
