• Coatings

    Nanocarriers have enabled the controlled release of many compounds which are instable or cannot enter the cells on their own.

Nanocarriers have enabled the controlled release of many compounds which are instable or cannot enter the cells on their own. However, their use in vivo is hindered by the interference from blood cells which prevent the release of the carried compound in the target tissue.

Modification of nanovesicles and nanoparticles surfaces with polymers and biomaterials, among others, provides nanosystems with increased steric stability and resistance. Additionally, it allows in vivo delivery strategies like long-circulating particles/vesicles or resistance to gastric conditions for intestinal release. Although there are many possibilities regarding nanoparticle or nanovesicle coatings, excellent examples are chitosan and PEG.

  • Chitosan is a great option to consider when coating liposomes. It forms polyelectrolyte layers by the interaction of chitosan (positive) with the surface of the liposomes (negative). That causes the nanovesicles to be more stable and mucoadhesive. Not only that but also it shows great biocompatible properties such as biodegradability and non-toxicity.
  • Other hydrophilic polymers or glycolipids like PEG or GM1 help in removing unwanted interactions. Those have a flexible chain that occupy the space immediately adjacent to the nanovesicle or nanoparticle surface. As a consequence, it excludes other macromolecules from this space. Blood plasma opsonins cannot bind anymore to the nanocarrier, thus avoiding macrophage unspecific interactions.

KEY BENEFITS

  • Reduction in frequency of drug administration
  • Improved patient compliance
  • Fluctuation reduction in blood drug level
  • Reduction in total drug usage when compared with conventional therapy
  • Reduction in drug accumulation with chronic therapy
  • Reduction in drug toxicity (local/systemic)
  • Drug increased efficacy
  • Reduced doses
  • Economical to the health care providers++3

SOME EXAMPLES:

  • Molecular therapy: Introducing genetic material in the cells can be done with the help of nanosystems. Nanocarriers functionalized with chitosan and PEG improve the delivery of the therapeutic material whether it is RNA (siRNA, pRNA, miRNA) or DNA. Results show increased cellular uptake and gene silencing, therefore improving therapy efficiency.
  • Wound healing: Chitosan coatings show antibacterial properties, which have made of them great wound healing and dressing materials. It has been used in combination with antibiotics to enhance the inhibition of bacterial growth, especially in the case of antibiotic-resistant strains. Findings show that they help wound healing and fasten tissue regeneration.
  • Cancer therapy: Many antitumoral compounds have been encapsulated in liposomes. Studies have proved that PEGylated liposomes have enhanced circulation time and antitumoral activity, reduced toxicity, and a more sustained release.
  • Ocular drug delivery: Both PEG and chitosan coatings have been used to increase the effectiveness of drug delivery into the ocular tissue. The mucoadhesive properties of chitosan combined with the long-term delivery of the PEG make both coatings ideal for this purpose.
  • Brain drug delivery: Functionalized nanoparticles have proved to be effective in delivering compounds through the blood brain barrier, which would not be possible with naked compounds. Chitosan coating mimics the brain composition and allows access through the blood brain barrier.
  • Intranasal administration: Not only does nasal administration allow easy access to certain organs like the brain or the lungs, but also to the blood stream. It is characterized by its rapid systemic absorption and higher drug bioavailability than other non-invasive administration routes. In this case, the coating of nanoparticles/nanovesicles carrying the drug is of great importance to deliver the compound of interest accurately in the target.