Elucidation of cellular uptake and intracellular trafficking of heparosan polysaccharide-based micelles in various cancer cells

Actively Targeting Redox-Responsive Multifunctional Micelles for Synergistic Chemotherapy of Cancer

Stimuli-responsive polymeric micelles decorated with cancer biomarkers represent an optimal choice for drug delivery applications due to their ability to enhance therapeutic efficacy while mitigating adverse side effects. Accordingly, we synthesized a digoxin-modified novel multifunctional redox-responsive disulfide-linked poly(ethylene glycol-b-poly(lactic-co-glycolic acid) copolymer (Bi(Dig-PEG-PLGA)-S2) for the targeted and controlled release of doxorubicin (DOX) in cancer cells. Within the micellar aggregate, the disulfide bond confers redox responsiveness, while the presence of the digoxin moiety acts as a targeting agent and chemosensitizer for DOX. Upon self-assembly in aqueous solution, Bi(Dig-PEG-PLGA)-S2 formed uniformly distributed spherical micelles with a hydrodynamic diameter (D h ) of 58.36 ± 0.78 nm and a zeta potential of -24.71 ± 1.01 mV. The micelles exhibited desirable serum and colloidal stability with a substantial drug loading capacity (DLC) of 6.26% and an encapsulation efficiency (EE) of 83.23%. In addition, the release of DOX demonstrated the redox-responsive behavior of the micelles, with approximately 89.41 ± 6.09 and 79.64 ± 6.68% of DOX diffusing from DOX@Bi(Dig-PEG-PLGA)-S2 in the presence of 10 mM GSH and 0.1 mM H2O2, respectively, over 96 h. Therefore, in HeLa cell lines, DOX@Bi(Dig-PEG-PLGA)-S2 showed enhanced intracellular accumulation and subsequent apoptotic effects, attributed to the targeting ability and chemosensitization potential of digoxin. Hence, these findings underscore the promising characteristics of Bi(Dig-PEG-PLGA)-S2 as a multifunctional drug delivery vehicle for cancer treatment.

Uptake Pathway of Styrene Maleic Acid Copolymer-Coated Lipid Emulsions Under Acidic Tumor Microenvironment

The purpose of this study was to elucidate and compare styrene maleic acid copolymer (SMA)-coated lipid emulsions (SMA emulsions) uptake pathway in vascular endothelial cells and surrounding cancer cells under not only neutral but also acidic pH, which is often observed in tumor microenvironment. DiI-labeled SMA emulsions were prepared using 1-palmitoyl-2-oleoyl-sn‑glycero-3-phosphocholine and triolein. In murine melanoma B16-BL6 (B16) cells and human umbilical vein endothelial cells (HUVEC), DiI-labeled SMA emulsions uptake under near-neutral (pH 7.4) and acidic (pH 6.0) conditions was determined by fluorescent analysis. SMA emulsions were taken up more efficiently into HUVEC than B16 cells under acidic condition in a temperature-dependent manner. Uptake study using endocytosis inhibitors showed that SMA emulsions were taken up by macropinocytosis and clathrin-mediated endocytosis in B16 cells. In HUVEC, however, they were taken up by clathrin- and caveolae-independent, but dynamin-dependent pathway. SMA emulsions would be internalized efficiently into vascular endothelial cells as well as cancer cells under acidic microenvironment via different endocytosis pathways. SMA emulsions could be a promising drug delivery carrier for anti-angiogenic drugs.

Construction of intelligent drug delivery system based on polysaccharide-derived polymer micelles: A review

Micelles are nanostructures developed via the spontaneous assembly of amphiphilic polymers in aqueous systems, which possess the advantages of high drug stability or active-ingredient solubilization, targeted transport, controlled release, high bioactivity, and stability. Polysaccharides have excellent water solubility, biocompatibility, and degradability, and can be modified to achieve a hydrophobic core to encapsulate hydrophobic drugs, improve drug biocompatibility, and achieve regulated delivery of the loaded drug. Micelles drug delivery systems based on polysaccharides and their derivatives show great potential in the biomedical field. This review discusses the principles of self-assembly of amphiphilic polymers and the formation of micelles; the preparation of amphiphilic polysaccharides is described in detail, and an overview of common polysaccharides and their modifications is provided. We focus on the review of strategies for encapsulating drugs in polysaccharide-derived polymer micelles (PDPMs) and building intelligent drug delivery systems. This review provides new research directions that will help promote future research and development of PDPMs in the field of drug carriers.

Enhancement of Oral Bioavailability of Protein and Peptide by Polysaccharide-based Nanoparticles

Oral drug delivery is a prevalent and cost-effective method due to its advantages, such as increased drug absorption surface area and improved patient compliance. However, delivering proteins and peptides orally remains a challenge due to their vulnerability to degradation by digestive enzymes, stomach acids, and limited intestinal membrane permeability, resulting in poor bioavailability. The use of nanotechnology has emerged as a promising solution to enhance the bioavailability of these vital therapeutic agents. Polymeric NPs, made from natural or synthetic polymers, are commonly used. Natural polysaccharides, such as alginate, chitosan, dextran, starch, pectin, etc., have gained preference due to their biodegradability, biocompatibility, and versatility in encapsulating various drug types. Their hydrophobic-hydrophilic properties can be tailored to suit different drug molecules.

Recent developments on natural polysaccharides as potential anti-gastric cancer substance: Structural feature and bioactivity

Gastric cancer (GC) is being a serious threat to human health. Seeking safer and more effective ingredients for anti-GC is of significance. Increasing natural polysaccharides (NPs) have been demonstrated to possess anti-GC activity. However, the information on anti-GC NPs is scattered. For well-understanding the potential of NPs as anti-GC substances, the recent developments on structure, bioactivity and mechanism of anti-GC NPs were comprehensively reviewed in this article. Meanwhile, the structure-activity relationship was discussed. Recent studies indicated that anti-GC NPs could be mainly divided into glucan and heteropolysaccharide, whose structures affected by sources and protocols of extraction and purification. NPs exhibited anti-GC activities in cell and animal experiments as well as clinical trials, and the mechanisms might be anti-proliferation, inducing apoptosis, anti-metastasis and anti-invasion, inducing autophagy, boosting immunity, anti-angiogenesis, reducing drug resistance, anti-angiogenesis, improving antioxidant level and changing metabolites. Moreover, structural features included molecular weight, functional groups, uronic acid and monosaccharide composition, glycosidic linkage type, and degree of branching and conformation might influence the activities. Otherwise, modifications could enhance the anti-GC activity of NPs, and anti-GC NPs could be combinedly used with chemotherapeutic drugs. This review supports the applications of NPs in anti-GC and provides theoretical basis for future study.

Heparosan-based self-assembled nanocarrier for zinc(II) phthalocyanine for use in photodynamic cancer therapy

Zinc(II) phthalocyanine (ZnPc) is a promising photosensitizer in photodynamic therapy (PDT) for melanoma treatment. However, the poor solubility of ZnPc limits its application. To overcome this limitation, heparosan (HP)-based nanoparticles were prepared by anchoring the l-lysine-linked α-linolenic acid branch to the carboxylic acid group to produce amphiphilic conjugates named heparosan with an l-lysine-linked α-linolenic acid branch (HLA). HLA conjugates could self-assemble into spherical nanoparticles in aqueous media and encapsulate ZnPc to form HLA-ZnPc nanoparticles. The cellular uptake of ZnPc could be improved by HLA carriers. These nanoparticles presented excellent photodynamic-mediated toxicity against mouse melanoma cells (B16) by markedly upregulating the intracellular reactive oxygen species (ROS) levels while showing no cytotoxicity to either B16 or normal cells (L02 and HK-2 cells) in the dark. Furthermore, HLA-ZnPc displayed excellent stability in both powder and Roswell Park Memorial Institute (RPMI) 1640 medium, indicating its promise for application in drug delivery and PDT. These results revealed a strategy for HP-based enhancement of ZnPc in PDT efficacy.

Advanced Research in Cellular Pharmacokinetics and its Cutting-edge Technologies

Pharmacokinetics (PK), as a significant part of pharmacology, runs through the overall process of the preclinical and clinical research on drugs and plays a significant role in determining the material basis of efficacy and mechanism research. However, due to the limitations of classical PK, cellular PK was put forward and developed rapidly. Many novel and original technologies have been innovatively applied to cellular PK research, thereby providing powerful technical support. As a novel field of PK research, cellular PK expands the research object and enriches the theoretical framework of PK. It provides a new perspective for elucidating the mechanism of drug action and the dynamic process of drug in the body. Furthermore, it provides a scientific basis and guiding significance for the development of new drugs and clinical rational drug use. Cellular PK can explain the dynamic process of certain drugs (e.g., antineoplastic drugs and antibiotics) and the disposition kinetics characteristics in some specific tissues (e.g., brain and tumor) in a clearer and more accurate manner. It is a beneficial supplement and the perfection of traditional PK. In the future, traditional and cellular PKs will complement each other well and improve into an all-around research system in drug developments. Briefly, this paper reviews the conceptual development of cellular PK and key associated technologies, explores its main functions and applications, and looks forward to the important pioneering significance and promising value for the development of PK.

Size-adjustable self-assembled nanoparticles through microfluidic platform promotes neuronal differentiation of mouse embryonic stem cells

Neuronal differentiation from stem cells is one of the most potent therapeutic approaches for recovering neurological function in individuals with neurodegenerative disorders. Herein, an on-demand intracellular retinoic acid released nanoparticles with tunable size and accurately controlled physico-biological properties have been prepared for achieving efficient neuronal differentiation. The amphiphilic chitosan oligosaccharide-cholesterol copolymers were synthesized by varying cholesterol content and self-assembled into spherical micelle in a microfluidic chip with different flow rates. Notably, the results indicated that by increasing the lipophilicity of the chitosan chain as well as mixing rate, the size of micelles was decreased. Retinoic acid (RA) was efficiently encapsulated in the core of micelles. The retinoic acid-containing nanoparticles could escape lysosome, accumulate in the cytoplasm, and release payload with a sustained pattern. The cytotoxicity assay of free retinoic acid and retinoic acid-loaded formulations against P19 embryonic stem cells confirmed the desirable safety of micelles. The result obtained from the uptake study showed that internalization of micelles occurs predominantly via lipid-raft endocytosis in the presence of higher cholesterol content. Moreover, the intracellular RA release upregulated the expression levels of neuronal factors. The micelles described here offer a promising nanomedicine strategy for neuronal differentiation of stem cells.

Micelles as potential drug delivery systems for colorectal cancer treatment

Despite the significant progress in cancer therapy, colorectal cancer (CRC) remains one of the most fatal malignancies worldwide. Chemotherapy is currently the mainstay therapeutic modality adopted for CRC treatment. However, the long-term effectiveness of chemotherapeutic drugs has been hampered by their low bioavailability, non-selective tumor targeting mechanisms, non-specific biodistribution associated with low drug concentrations at the tumor site and undesirable side effects. Over the last decade, there has been increasing interest in using nanotechnology-based drug delivery systems to circumvent these limitations. Various nanoparticles have been developed for delivering chemotherapeutic drugs among which polymeric micelles are attractive candidates. Polymeric micelles are biocompatible nanocarriers that can bypass the biological barriers and preferentially accumulate in tumors via the enhanced permeability and retention effect. They can be easily engineered with stimuli-responsive and tumor targeting moieties to further ensure their selective uptake by cancer cells and controlled drug release at the desirable tumor site. They have been shown to effectively improve the pharmacokinetic properties of chemotherapeutic drugs and enhance their safety profile and anticancer efficacy in different types of cancer. Given that combination therapy is the new strategy implemented in cancer therapy, polymeric micelles are suitable for multidrug delivery and allow drugs to act concurrently at the action site to achieve synergistic therapeutic outcomes. They also allow the delivery of anticancer genetic material along with chemotherapy drugs offering a novel approach for CRC therapy. Here, we highlight the properties of polymeric micelles that make them promising drug delivery systems for CRC treatment. We also review their application in CRC chemotherapy and gene therapy as well as in combination cancer chemotherapy.

Holden, Donahue ND, Green DE, Frickenstein AN, Mettenbrink EM, Schwemley TA, Francek ER, Haddad M, Hossen MN, Mukherjee S, Wu S, DeAngelis PL, Wilhelm S. Nanoparticle Surface Engineering with Heparosan Polysaccharide Reduces Serum Protein Adsorption and Enhances Cellular Uptake

Nanoparticle modification with poly(ethylene glycol) (PEG) is a widely used surface engineering strategy in nanomedicine. However, since the artificial PEG polymer may adversely impact nanomedicine safety and efficacy, alternative surface modifications are needed. Here, we explored the "self" polysaccharide heparosan (HEP) to prepare colloidally stable HEP-coated nanoparticles, including gold and silver nanoparticles and liposomes. We found that the HEP-coating reduced the nanoparticle protein corona formation as efficiently as PEG coatings upon serum incubation. Liquid chromatography-mass spectrometry revealed the protein corona profiles. Heparosan-coated nanoparticles exhibited up to 230-fold higher uptake in certain innate immune cells, but not in other tested cell types, than PEGylated nanoparticles. No noticeable cytotoxicity was observed. Serum proteins did not mediate the high cell uptake of HEP-coated nanoparticles. Our work suggests that HEP polymers may be an effective surface modification technology for nanomedicines to safely and efficiently target certain innate immune cells.

Transport mechanism and subcellular localization of a polysaccharide from Cucurbia Moschata across Caco-2 cells model

Pumpkin polysaccharides with various bioactivities are mainly taken orally, thus detailed knowledge of the intestinal transport of which are essential for understanding its bioactivities. The Caco-2 cells monolayer model (mimic intestinal epithelium) was successfully constructed and Cucurbia moschata polysaccharides (PPc-F) were successfully conjugated with fluorescein isothiocyanate (FITC) to evaluate the transcellular transport mechanism and subcellular localization of PPc. The transport process of PPc-F was energy-dependent, and a moderately-absorbed biological macromolecule according to the apparent permeability coefficients (P_app) value. The endocytosis process of PPc-F in Caco-2 cells included the clathrin- and caveolae (or lipid draft)-medicated routes. And the translocation process was related to endoplasmic reticulum (ER), golgi apparatus (GA), tubulin and the acidification of endosomes. As for the intracellular location of PPc-F, it was mainly accumulated in ER. The study provided an understanding of the transmembrane transport of PPc-F, and could help studying the mechanisms of its effects.

Exploration and insights into the cellular internalization and intracellular fate of amphiphilic polymeric nanocarriers

The beneficial or deleterious effects of nanomedicines emerge from their complex interactions with intracellular pathways and their subcellular fate. Moreover, the dynamic nature of plasma membrane accounts for the movement of these nanocarriers within the cell towards different organelles thereby not only influencing their pharmacokinetic and pharmacodynamic properties but also bioavailability, therapeutic efficacy and toxicity. Therefore, an in-depth understanding of underlying parameters controlling nanocarrier endocytosis and intracellular fate is essential. In order to direct nanoparticles towards specific sub-cellular organelles the physicochemical attributes of nanocarriers can be manipulated. These include particle size, shape and surface charge/chemistry. Restricting the particle size of nanocarriers below 200 nm contributes to internalization via clathrin and caveolae mediated pathways. Similarly, a moderate negative surface potential confers endolysosomal escape and targeting towards mitochondria, endoplasmic reticulum (ER) and Golgi. This review aims to provide an insight into these physicochemical attributes of nanocarriers fabricated using amphiphilic graft copolymers affecting cellular internalization. Fundamental principles understood from experimental studies have been extrapolated to draw a general conclusion for the designing of optimized nanoparticulate drug delivery systems and enhanced intracellular uptake via specific endocytic pathway.

Strategies for Delivering Nanoparticles across Tumor Blood Vessels

Nanoparticle transport across tumor blood vessels is a key step in nanoparticle delivery to solid tumors. However, the specific pathways and mechanisms of this nanoparticle delivery process are not fully understood. Here, the biological and physical characteristics of the tumor vasculature and the tumor microenvironment are explored and how these features affect nanoparticle transport across tumor blood vessels is discussed. The biological and physical methods to deliver nanoparticles into tumors are reviewed and paracellular and transcellular nanoparticle transport pathways are explored. Understanding the underlying pathways and mechanisms of nanoparticle tumor delivery will inform the engineering of safer and more effective nanomedicines for clinical translation.

High density fermentation of probiotic E. coli Nissle 1917 towards heparosan production, characterization, and modification

Heparosan is a naturally occurring non-sulfated glycosaminoglycan. Heparosan serves as the substrate for chemoenzymatic synthesis of biopharmaceutically important heparan sulfate and heparin. Heparosan is biologically inert molecule, non-toxic, and non-immunogenic and these qualities of heparosan make it an ideal drug delivery vehicle. The critical-to-quality (CTQ) attributes for heparosan applications include composition of heparosan, absence of any unnatural moieties, and heparosan molecular weight size and unimodal distribution. Probiotic bacteria E. coli Nissle 1917 (EcN) is a natural producer of heparosan. The current work explores production of EcN heparosan and process parameters that may impact the heparosan CTQ attributes. Results show that EcN could be grown to high cell densities (OD₆₀₀ 160-180) in a chemically defined media. The fermentation process is successfully scaled from 5-L to 100-L bioreactor. The chemical composition of heparosan from EcN was confirmed using nuclear magnetic resonance. Results demonstrate that heparosan molecular weight distribution may be influenced by fermentation and purification conditions. Size exclusion chromatography analysis shows that the heparosan purified from fermentation broth results in bimodal distribution, and cell-free supernatant results in unimodal distribution (average molecular weight 68,000 Da). The yield of EcN-derived heparosan was 3 g/L of cell free supernatant. We further evaluated the application of Nissle 1917 heparosan for chemical modification to prepare N-sulfo heparosan (NSH), the first intermediate precursor for heparin and heparan sulfate. KEY POINTS: • High cell density fermentation, using a chemically defined fermentation media for the growth of probiotic bacteria EcN (E. coli Nissle 1917, a natural producer of heparosan) is reported. • Process parameters towards the production of monodispersed heparosan using probiotic bacteria EcN (Nissle 1917) has been explored and discussed. • The media composition and the protocol (SOPs and batch records) have been successfully transferred to contract manufacturing facilities and industrial partners.

New Means to Control Molecular Assembly

While self-assembly of molecules is relatively well-known and frequently utilized in chemical synthesis and material science, controlled assembly of molecules represents a new concept and approach. The present work demonstrates the concept of controlled molecular assembly using a non-spherical biomolecule, heparosan tetrasaccharide (MW = 1.099 kD). The key to controlled assembly is the fact that ultra-small solution droplets exhibit different evaporation dynamics from those of larger ones. Using an independently controlled microfluidic probe in an atomic force microscope, sub-femtoliter aqueous droplets containing designed molecules produce well-defined features with dimensions as small as tens of nanometers. The initial shape of the droplet and the concentration of solute within the droplet dictate the final assembly of molecules due to the ultrafast evaporation rate and dynamic spatial confinement of the droplets. The level of control demonstrated in this work brings us closer to programmable synthesis for chemistry and materials science which can be used to develop vehicles for drug delivery three-dimensional nanoprinting in additive manufacturing.

Biodegradable reduction-responsive polymeric micelles for enhanced delivery of melphalan to retinoblastoma cells

Melphalan (MEL) is an effective chemotherapeutic agent for treatment of retinoblastoma (Rb) which is the most common childhood malignancy. However, the inherent cardiopulmonary toxicity and hazardous integration limit its therapeutic effect on RB. N-Acetylheparosan (AH), a natural heparin-like polysaccharide in mammals with long circulation effect and good biocompatibility, was linked by d-α-tocopherol acid succinate (VES) via and cystamine (CYS) to synthesize reduction-responsive N-acetylheparosan-CYS-Vitamin E succinate (AHV) copolymers. In addition, CYS was replaced by adipic acid dihydrazide (ADH) to obtain a control of non-reduction-responsive polymers N-acetylheparosan-ADH-Vitamin E succinate (ADV). MEL-loaded AHV micelles (MEL/AHV) as well as ADV micelles (MEL/ADV) were prepared with small particle size and high drug loading content. In vitro drug release showed that MEL/AHV micelles presented obvious reduction-triggered release behavior compared with MEL/ADV. In vitro antitumor effects were investigated using WERI-Rb-1 retinoblastoma cells. Cytotoxicity experiments showed that the IC₅₀ of MEL/AHV was significantly lower than that of free MEL and MEL/ADV, suggesting that MEL/AHV enhanced the cytotoxicity against retinoblastoma cells. Furthermore, MEL/AHV micelles were more easily uptaken by multiple pathways compared with MEL/ADV and free MEL. Therefore, MEL/AHV might be a potential delivery system for enhanced delivery of melphalan to Rb cells.

Heparosan as a potential alternative to hyaluronic acid for the design of biopolymer-based nanovectors for anticancer therapy

Glycosaminoglycans (GAGs) are important components of the extracellular matrix that have attracted great interest for drug delivery and pharmaceutical applications due to their diverse biological functions. Among GAGs, heparosan (Hep), a biosynthetic precursor of heparin, has recently emerged as a promising building block for the design of nanoparticles with stealth properties. Though this non-sulfated polysaccharide has a chemical structure very close to that of hyaluronic acid (HA), it distinguishes from HA in that it is biologically inert in the extracellular spaces in the body. In this study, we designed Hep- and HA-based nanogels (NGs) that differ only in the chemical nature of the hydrophilic shell. The nanogels were prepared in a very straightforward way from Hep and HA modified with a thermoresponsive copolymer properly designed to induce self-assembly below room temperature. This versatile synthetic approach also enabled further shell-crosslinking allowing an increase in the colloidal stability. After careful characterization of the un-crosslinked and crosslinked Hep and HA NGs in terms of size (Z-average diameters of un-crosslinked and crosslinked NGs ∼110 and 150 nm) and morphology, they were injected intravenously into tumor-bearing mice for biodistribution experiments. Interestingly, these show that the liver uptake of Hep nanogels is remarkably reduced and tumor accumulation significantly improved as compared to HA nanogels (intensity ratios of tumor-to-liver of 2.2 and 1.4 for the un-crosslinked and crosslinked Hep NGs versus 0.11 for the un-crosslinked and crosslinked HA ones). These results highlight the key role played by the shell-forming GAGs on the in vivo fate of nanogels, which correlates with the specific biological properties of Hep and HA.