Recent Progress in Bioconjugation Strategies for Liposome-Mediated Drug Delivery

Abstract

In nanoparticle (NP)-mediated drug delivery, liposomes are the most widely used drug carrier, and the only NP system currently approved by the FDA for clinical use, owing to their advantageous physicochemical properties and excellent biocompatibility. Recent advances in liposome technology have been focused on bioconjugation strategies to improve drug loading, targeting, and overall efficacy. In this review, we highlight recent literature reports (covering the last five years) focused on bioconjugation strategies for the enhancement of liposome-mediated drug delivery. These advances encompass the improvement of drug loading/incorporation and the specific targeting of liposomes to the site of interest/drug action. We conclude with a section highlighting the role of bioconjugation strategies in liposome systems currently being evaluated for clinical use and a forward-looking discussion of the field of liposomal drug delivery.

Liposome Photosensitizer Formulations for Effective Cancer Photodynamic Therapy

“…They are self-assembled in an aqueous medium, with the assistance of hydrophobic interaction, developing a sealed structure formed of one or more lamella having the hydrophilic heads oriented towards the outer surfaces of the lamella and the hydrophobic tails founding the lamella interiors. This forms an aqueous core inside the liposomes ( Figure 3 ) [ 49 , 50 ]. Liposomes are prepared using diverse types of naturally occurring phospholipids, which are biocompatible and biodegradable ( Table 1 ).…”

“…They are prepared by the self-assembly of phospholipids and/or tetraethers lipids which are biocompatible and biodegradable [ 44 ]. Moreover, liposomes can: (i) Accommodate hydrophilic and hydrophobic agents (such as proteins, nucleic acids, chemotherapeutics, and various PSs); (ii) be decorated and bioconjugated with various functional groups and surface targeting moieties (such as proteins, polymers, and peptides), which would improve their physicochemical properties, drug loading, clearance and/or trigger the release of their cargos into the target tissue; (iii) minimize the opsonization phenomenon by being less identifiable by the reticuloendothelial system leading to prolonging the half-life of the host molecules in the systemic circulation (>48 h) and facilitating the preferential passive accumulation inside tumor tissues; and (iv) widen the therapeutic index for most drugs ( Figure 3 ) [ 44 , 45 , 46 , 47 , 48 , 49 ]. Liposomes can enter the cancer cells either by endocytosis or via membrane fusion.…”

“…Blood vessels in healthy tissues are organized and tightly packed, which prevents the extravasation of liposomes. On the other hand, the blood vessels of tumor tissues are disorganized, due to the rapid proliferation of the vascular endothelium inside the tumor tissues [ 44 , 45 , 46 , 47 , 48 , 49 , 50 , 51 , 52 , 53 , 54 , 55 , 56 ]. Furthermore, the lymphatic drainage is impaired inside the tumor tissue, resulting in the overexpression of permeability mediators, such as bradykinin, nitric oxide, and prostaglandins, which increase EPR [ 56 ].…”

“…Liposomes are spherical vesicles with an aqueous inner core enclosed by one or more phospholipid bilayers which permit the conjugation of various functional groups. Reproduced with permission from[49].…”

Recent Advancements in Polymer/Liposome Assembly for Drug Delivery: From Surface Modifications to Hybrid Vesicles

“…In addition to the steric stabilization, the grafting of polymers into the lipid bilayer increases the hydrophilicity of the liposome and their subsequent stability in an aqueous environment [69], and influences liposome permeability and physicochemical properties such as drug loading and leakage [70] (Figure 4). For example, PEGylated liposomes have been found to possess high drug loading capacities up to 90% [71,72].…”