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Assuming that polyethylene glycol (PEG)-conjugated or PEGylated nanocarriers always offer outstanding physicochemical properties and pharmacokinetics profiles when compared to non-PEGylated ones, is not always accurate. For example, drug-loaded PEGylated nanocarriers for the treatment of cancer will not magically escape the reticuloendothelial system (RES) sequestration and clearance, benefit from the enhanced permeability and retention (EPR) effect of the tumor leaky vasculature and preferentially accumulate in the target tissue or cells. This is too good to be true. In this review, several drawbacks of PEGylation will be discussed; for example, how PEGylation can give rise to unfavourable physicochemical characteristics (e. g. particle size and release patterns) and post in vivo administration limitations of the formulated nanocarriers (e. g. limited evasion of RES uptake, development of hypersensitivity reactions, reduced intracellular accumulation and interference with the subcellular processing of nanocarriers necessary to produce the intended pharmacological effect).This review aims at providing better understanding of the pros and cons of PEGylation, encouraging the use of PEGylation with caution, avoiding the assumption that PEGylation will provide all advantages needed to deliver nanocarriers to the target tissue and looking for alternatives to optimize nanocarriers’ utilization especially in the delivery of chemotherapeutic agents for the treatment of different types of cancer. This review comprises a summary of some of the reported literature between 2013 and 2018 using different search engines; PubMed, Science Direct and Google Scholar, and the keywords listed below.

Background and Purpose Metabolic reprogramming “Warburg effect” and immune checkpoint signaling are immunosuppressive hallmarks of Triple-Negative Breast Cancer (TNBC) contributing to the limited clinical applicability of immunotherapy. Biomaterials arise as novel tools for immunomodulation of the tumor microenvironment (TME) that can be used alongside conventional immunotherapeutics. Chitosan and lecithin are examples of versatile biomaterials with interesting immunomodulatory properties. In this study, we aimed at investigation of the role of carefully designed hybrid nanoparticles (NPs) on common mediators of both PD-L1 expression and glycolytic metabolism. Materials and Methods Hybrid lecithin-chitosan NPs were prepared and characterized. Their intracellular concentration, localization and effect on the viability of MDA-MB-231 cells were assessed. Glycolytic metabolism was quantified by measuring glucose consumption, ATP generation, lactate production and extracellular acidification. Nitric oxide (NO) production was quantified using Greiss reagent. Gene expression of iNOS, PI3K, Akt, mTOR, HIF-1α and PD-L1 was quantified by reverse transcription and q-RT-PCR. Results Chitosan, lecithin and the NPs-formulated forms have been shown to influence the “Warburg effect” and immune checkpoint signaling of TNBC cells differently. The composition of the hybrid systems dictated their subcellular localization and hence the positive or negative impact on the immunosuppressive characteristics of TNBC cells. Conclusions Carefully engineered hybrid lecithin-chitosan NPs could convert the immune-suppressive microenvironment of TNBC to an immune-active microenvironment via reduction of PD-L1 expression and reversal of the Warburg effect.

Introduction Protein corona (PC) deposition on nanoparticles (NPs) in biological systems contributes to a great extent to NPs’ fates; their targeting potential, the interaction with different biological systems and the subsequent functions. PC – when properly tuned – can serve as a potential avenue for optimization of NPs’ use in cancer therapy. Methods Poly-lactic co-glycolic acid (PLGA)-based NPs exhibiting different physicochemical properties were fabricated and characterized. The PC makeup of these NPs were qualitatively and quantitatively analyzed by Western blot and Bradford assay, respectively. The effect of PC on the release of NPs’ cargos and the intracellular uptake into B16F10 melanoma cells has been studied. Results The composition of NPs (polymeric PLGA NPs vs lipid-polymer hybrid NPs) and the conjugation of an active targeting ligand (cRGDyk peptide) represented the major determinants of the PC makeup of NPs. The in vitro release of the loaded cargos from the NPs depended on the PC and the presence of serum proteins in the release medium. Higher cumulative release has been recorded in the presence of proteins in the case of peptide conjugated NPs, cNPs, while the unconjugated formulations, uNPs, showed an opposite pattern. NPs intracellular uptake studies revealed important roles of distinct serum and cellular proteins on the extent of NPs’ accumulation in melanoma cells. For example, the abundance of vitronectin (VN) protein from serum has been positively related to the intracellular accumulation of the NPs. Conclusion Careful engineering of nanocarriers can modulate the recruitment of some proteins suggesting a potential use for achieving endogenous targeting to overcome the current limitations of targeted delivery of chemotherapeutic agents.