Cell membrane coated nanocarriers - an efficient biomimetic platform for targeted therapy.

Targeted therapy approaches have become the core of modern translational science and as an intriguing field, it is the solution of the conventional drug delivery problems that were once unanswered. Traditional methods of delivering drugs and therapeutics faced issues of solubility, sustained release, not enough amount getting through the diseased site, for e.g a tumor. Various formulations of liposomes, polymers, dendrimers, etc have succeeded and made their way for clinical trials trying to enhance the pharmacokinetic and biodistribution of the drug. Many stealth coatings that include hydrophilic polymers (PEG, chitosan, polyacrylamides, etc) can act as a covering around the nanoparticle that can shield the surface from aggregation, opsonization and evade immune system, thus considered in Generally Recognized as Safe (GRAS) category. Several other polymers such as poly-2-oxazoline, polyethylene oxide, PEG-based surfactant (polysorbate-80), and zwitterionic phospholipids have also been tested for their antifouling properties. However, the polymer coating approach requires labor-intensive procedures and conjugation chemistries that often fail in mice model. Besides, due to immunogenicity and allergic reactions evoked by the PEG-coated nanoparticles, there was an urge to find biomimicking materials that can prove better as shielding agents which paved the way for cell membrane coated nanoparticles (CMCNPs) to come into the limelight. CMCNPs consist of a nanoparticle inner core covered by cell membrane that can be implicated in targeted drug delivery approaches, photothermal therapy, diagnosis or imaging making it a powerful theranostic tool. In this review, mode of preparation of CMCNPs, different sources of cell membranes (RBCs, WBCs, platelets, cancer cells, stem cells with some other unconventional sources) and nanoparticle cores that are employed have been thoroughly emphasized. In addition to this, advancements and limitations with respect to this newly emerging field have been focussed.