Conjugation of Bioactive Ligands to PEG-Grafted Chitosan at the Distal End of PEG

Folate Conjugated Polyethylene Glycol Probe for Tumor-Targeted Drug Delivery of 5-Fluorouracil

A targeted delivery system is primarily intended to carry a potent anticancer drug to specific tumor sites within the bodily tissues. In the present study, a carrier system has been designed using folic acid (FA), bis-amine polyethylene glycol (PEG), and an anticancer drug, 5-fluorouracil (5-FU). FA and PEG were joined via an amide bond, and the resulting FA-PEG-NH2 was coupled to 5-FU producing folate-polyethylene glycol conjugated 5-fluorouracil (FA-PEG-5-FU). Spectroscopic techniques (UV-Vis, 1HNMR, FTIR, and HPLC) were used for the characterization of products. Prodrug (FA-PEG-5-FU) was analyzed for drug release profile (in vitro) up to 10 days and compared to a standard anticancer drug (5-FU). Folate conjugate was also analyzed to study its folate receptors (FR) mediated transport and in vitro cytotoxicity assays using HeLa cancer cells/Vero cells, respectively, and antitumor activity in tumor-bearing mice models. Folate conjugate showed steady drug release patterns and improved uptake in the HeLa cancer cells than Vero cells. Folate conjugate treated mice group showed smaller tumor volumes; specifically after the 15th day post-treatment, tumor sizes were decreased significantly compared to the standard drug group (5-FU). Molecular docking findings demonstrated importance of Trp138, Trp140, and Lys136 in the stabilization of flexible loop flanking the active site. The folic acid conjugated probe has shown the potential of targeted drug delivery and sustained release of anticancer drug to tumor lesions with intact antitumor efficacy.

Nanoparticles Targeting Innate Immune Cells in Tumor Microenvironment

A variety of innate immune cells such as macrophages, dendritic cells, myeloid-derived suppressor cells, natural killer cells, and neutrophils in the tumor microenvironments, contribute to tumor progression. However, while several recent reports have studied the use of immune checkpoint-based cancer immunotherapy, little work has focused on modulating the innate immune cells. This review focuses on the recent studies and challenges of using nanoparticles to target innate immune cells. In particular, we also examine the immunosuppressive properties of certain innate immune cells that limit clinical benefits. Understanding the cross-talk between tumors and innate immune cells could contribute to the development of strategies for manipulating the nanoparticles targeting tumor microenvironments.

Biotinylated chitosan macromolecule based nanosystems: A review from chemical design to biological targets

World Health Organization estimates that 30-50% of cancers are preventable by healthy lifestyle choices, early detection and adequate therapy. When the conventional therapeutic strategies are still regulated by the lack of selectivity, multidrug resistance and severe toxic side effects, nanotechnology grants a new frontier for cancer management since it targets cancer cells and spares healthy tissues. This review highlights recent studies using biotin molecule combined with functional nanomaterials used in biomedical applications, with a particular attention on biotinylated chitosan-based nanosystems. Succinctly, this review focuses on five areas of recent advances in biotin engineering: (a) biotin features, (b) biotinylation approaches, (c) biotin functionalized chitosan based nanosystems for drug and gene delivery functions, (d) diagnostic and theranostic perspectives, and (e) author's inputs to the biotin-chitosan based tumour-targeting drug delivery structures. Precisely engineered biotinylated-chitosan macromolecules shaped into nanosystems are anticipated to emerge as next-generation platforms for treatment and molecular imaging modalities applications.

Nanoparticles for dendritic cell-based immunotherapy

Crosstalk among immune cells has attracted considerable attention with the advent of immunotherapy as a novel therapeutic approach for challenging diseases, especially cancer, which is the leading cause of mortality worldwide. Dendritic cells-the key antigen-presenting cells-play a pivotal role in immunological response by presenting exogenous epitopes to T cells, which induces the self-defense mechanisms of the body. Furthermore, nanotechnology has provided promising ways for diagnosing and treating cancer in the last decade. The progress in nanoparticle drug carrier development, combined with enhanced understanding of the immune system, has enabled harnessing of anti-tumor immunity. This review focuses on the recent advances in nanotechnology that have improved the therapeutic efficacy of immunotherapies, with emphasis on dendritic cell physiology and its role in presenting antigens and eliciting therapeutic T cell response.

Preparation and Characterization of Biocompatible Chitosan Nanoparticles for Targeted Brain Delivery of Peptides

Here, we describe a nanocarrier system that can transfer chitosan nanoparticles loaded with either small peptides such as the caspase inhibitor Z-DEVD-FMK or a large peptide like basic fibroblast growth factor across the blood-brain barrier. The nanoparticles are selectively directed to the brain and are not measurably taken up by the liver and spleen. Intravital fluorescent microscopy provides an opportunity to study the penetration kinetics of nanoparticles loaded with fluorescent agents such as Nile red. Nanoparticles functionalized with anti-transferrin antibody and loaded with peptides efficiently provided neuroprotection when systemically administered either as a formulation bearing a single peptide or a mixture of them. Failure of brain permeation of the nanoparticles after inhibition of vesicular transcytosis by imatinib as well as when nanoparticles were not functionalized with anti-transferrin antibody indicates that this nanomedicine formulation is rapidly transported across the blood-brain barrier by receptor-mediated transcytosis.

Triethylene glycol-modified iridium(iii) complexes for fluorescence imaging of Schistosoma japonicum

Schistosomiasis, an infectious disease caused by the Schistosoma parasitic worm, presents a serious public health issue. To date, investigation of anti-Schistosomiasis drug mechanisms through fluorescence imaging remains challenging due to the lack of appropriate dyes as fluorescent probes. Phosphorescent Ir(iii) complexes have been attracting substantial attention among various classes of fluorophores given their excellent photophysical properties. Herein, four phosphorescent Ir(iii) complexes were synthesized, two of which contained a triethylene glycol (TEG) hydrophilic group. The phosphorescent emission range of the four complexes lay between 500 and 750 nm, and their quantum yields ranged from 0.031 to 0.146. Furthermore, under the experimental concentration conditions, the TEG-modified complexes had low cytotoxicity. Cell fluorescence labeling experiments indicated that the TEG-modified complexes had good membrane permeability. Finally, the TEG-modified complexes showed remarkable labeling effects in adult Schistosoma fluorescence imaging. Thus, TEG-modified Ir(iii) complexes could be used as a new class of bilharzial fluorescent probes.

Morphogenic Peptides in Regeneration of Load Bearing Tissues

Morphogenic proteins due to their short half-life require high doses of growth factors in regeneration of load bearing tissues which leads to undesirable side effects. These side effects include bone overgrowth, tumor formation and immune reaction. An alternative approach to reduce undesirable side effects of proteins in regenerative medicine is to use morphogenic peptides derived from the active domains of morphogenic proteins or soluble and insoluble components of the extracellular matrix of mineralized load bearing tissues to induce differentiation of progenitor cells, mineralization, maturation and bone formation. In that regard, many peptides with osteogenic activity have been discovered. These include peptides derived from bone morphogenic proteins (BMPs), those based on interaction with integrin and heparin-binding receptors, collagen derived peptides, peptides derived from other soluble ECM proteins such as bone sialoprotein and enamel matrix proteins, and those peptides derived from vasculoinductive and neuro-inductive proteins. Although these peptides show significant osteogenic activity in vitro and increase mineralization and bone formation in animal models, they are not widely used in clinical orthopedic applications as an alternative to morphogenic proteins. This is partly due to the limited availability of data on structure and function of morphogenic peptides in physiological medium, particularly in tissue engineered scaffolds. Due to their amphiphilic nature, peptides spontaneously self-assemble and aggregate into micellar structures in physiological medium. Aggregation alters the sequence of amino acids in morphogenic peptides that interact with cell surface receptors thus affecting osteogenic activity of the peptide. Aggregation and micelle formation can dramatically reduce the active concentration of morphogenic peptides with many-fold increase in peptide concentration in physiological medium. Other factors that affect bioactivity are the non-specific interaction of morphogenic peptides with lipid bilayer of the cell membrane, interaction of the peptide with cell surface receptors that do not specifically induce osteogenesis leading to less-than-optimal osteogenic activity of the peptide, and less-than-optimal interaction of the peptide with osteogenic receptors on the cell surface. Covalent attachment or physical interaction with the tissue engineered matrix can also alter the bioactivity of morphogenic peptides and lead to a lower extent of osteogenesis and bone formation. This chapter reviews advances in discovery of morphogenic peptide, their structural characterization, and challenges in using morphogenic peptides in clinical applications as growth factors in tissue engineered devices for regeneration of load bearing tissues.

In vivo delivery of peptides and Toll-like receptor ligands by mannose-functionalized polymeric nanoparticles induces prophylactic and therapeutic anti-tumor immune responses in a melanoma model

We hypothesized that the co-entrapment of melanoma-associated antigens and the Toll-like receptor (TLR) ligands Poly(I:C) and CpG, known to be Th1-immunopotentiators, in mannose-functionalized aliphatic polyester-based nanoparticles (NPs) could be targeted to mannose receptors on antigen-presenting cells and induce anti-tumor immune responses. High entrapment efficiencies of antigens and immunopotentiators in 150nm NPs were obtained. The co-entrapment of the model antigen ovalbumin and the TLR ligands was crucial to induce high IgG2c/IgG1 ratios and high levels of IFN-γ and IL-2. Mannose-functionalization of NPs potentiated the Th1 immune response. The nanoparticulate vaccines decreased the growth rate of murine B16F10 melanoma tumors in therapeutic and prophylatic settings. The combination of mannose-functionalized NPs containing MHC class I- or class II-restricted melanoma antigens and the TLR ligands induced the highest tumor growth delay. Overall, we demonstrate that the multifunctional properties of NPs in terms of targeting and antigen/adjuvant delivery have high cancer immunotherapeutic potential.

Carbohydrate PEGylation, an approach to improve pharmacological potency

Conjugation with polyethylene glycol (PEG), known as PEGylation, has been widely used to improve the bioavailability of proteins and low molecular weight drugs. The covalent conjugation of PEG to the carbohydrate moiety of a protein has been mainly used to enhance the pharmacokinetic properties of the attached protein while yielding a more defined product. Thus, glycoPEGylation was successfully applied to the introduction of a PEGylated sialic acid to a preexisting or enzymatically linked glycan in a protein. Carbohydrates are now recognized as playing an important role in host–pathogen interactions in protozoal, bacterial and viral infections and are consequently candidates for chemotherapy. The short in vivo half-life of low molecular weight glycans hampered their use but methods for the covalent attachment of PEG have been less exploited. In this review, information on the preparation and application of PEG-carbohydrates, in particular multiarm PEGylation, is presented.

Immune system targeting by biodegradable nanoparticles for cancer vaccines

The concept of therapeutic cancer vaccines is based on the activation of the immune system against tumor cells after the presentation of tumor antigens. Nanoparticles (NPs) have shown great potential as delivery systems for cancer vaccines as they potentiate the co-delivery of tumor-associated antigens and adjuvants to dendritic cells (DCs), insuring effective activation of the immune system against tumor cells. In this review, the immunological mechanisms behind cancer vaccines, including the role of DCs in the stimulation of T lymphocytes and the use of Toll-like receptor (TLR) ligands as adjuvants will be discussed. An overview of each of the three essential components of a therapeutic cancer vaccine - antigen, adjuvant and delivery system - will be provided with special emphasis on the potential of particulate delivery systems for cancer vaccines, in particular those made of biodegradable aliphatic polyesters, such as poly(lactic-co-glycolic acid) (PLGA) and poly-ε-caprolactone (PCL). Some of the factors that can influence NP uptake by DCs, including size, surface charge, surface functionalization and route of administration, will also be considered.

Therapeutic angiogenesis: controlled delivery of angiogenic factors

Therapeutic angiogenesis aims at treating ischemic diseases by generating new blood vessels from existing vasculature. It relies on delivery of exogenous factors to stimulate neovasculature formation. Current strategies using genes, proteins and cells have demonstrated efficacy in animal models. However, clinical translation of any of the three approaches has proved to be challenging for various reasons. Administration of angiogenic factors is generally considered safe, according to accumulated trials, and offers off-the-shelf availability. However, many hurdles must be overcome before therapeutic angiogenesis can become a true human therapy. This article will highlight protein-based therapeutic angiogenesis, concisely review recent progress and examine critical challenges. We will discuss growth factors that have been widely utilized in promoting angiogenesis and compare their targets and functions. Lastly, since bolus injection of free proteins usually result in poor outcomes, we will focus on controlled release of proteins.

Improved bioavailability of inhibitors of Trypanosoma cruzi trans-sialidase: PEGylation of lactose analogs with multiarm polyethyleneglycol

The trans-sialidase of Trypanosoma cruzi (TcTS) catalyzes the transfer of sialic acid from host glycoconjugates to terminal β-galactopyranosides in the mucins of the parasite. During infection, the enzyme is actively shed by the parasite to the bloodstream inducing hematological alterations. Lactitol prevents cell apoptosis caused by the TcTS, although it is rapidly eliminated from the circulatory system. Linear polyethyleneglycol (PEG) conjugates of lactose analogs were prepared but their clearance from blood was still quite fast. With the aim of improving their circulating half-lives in vivo, we now synthesized covalent conjugates of eight-arm PEG. The star-shape of these conjugates allows an increase in the molecular weight together with the loading of the active sugar. Two approaches were used for PEGylation of disaccharide derivatives containing β-D-Galp as the non-reducing unit. (1) Amide formation between benzyl β-D-galactopyranosyl-(1→6)-2-amino-2-deoxy-α-D-glucopyranoside and a succinimide-activated PEG. (2) Conjugation of lactobionolactone with amino end-functionalized PEG. Two 8-arm PEG derivatives (20 and 40 kDa) were used for each sugar. Substitution of all arms was proved by (1)H nuclear magnetic resonance (NMR) spectroscopy. The bioavailability of the conjugates in mice plasma was considerably improved with respect to the 5 kDa linear PEG conjugates retaining their inhibitory properties.

PLGA-based nanoparticles: an overview of biomedical applications

Poly(lactic-co-glycolic acid) (PLGA) is one of the most successfully developed biodegradable polymers. Among the different polymers developed to formulate polymeric nanoparticles, PLGA has attracted considerable attention due to its attractive properties: (i) biodegradability and biocompatibility, (ii) FDA and European Medicine Agency approval in drug delivery systems for parenteral administration, (iii) well described formulations and methods of production adapted to various types of drugs e.g. hydrophilic or hydrophobic small molecules or macromolecules, (iv) protection of drug from degradation, (v) possibility of sustained release, (vi) possibility to modify surface properties to provide stealthness and/or better interaction with biological materials and (vii) possibility to target nanoparticles to specific organs or cells. This review presents why PLGA has been chosen to design nanoparticles as drug delivery systems in various biomedical applications such as vaccination, cancer, inflammation and other diseases. This review focuses on the understanding of specific characteristics exploited by PLGA-based nanoparticles to target a specific organ or tissue or specific cells.

Preparation of carboxymethylchitosan nanoparticles with Acid-sensitive bond based on solid dispersion of 10-hydroxycamptothecin

Solid dispersions were prepared by a conventional solvent evaporation method from the water-insoluble model drug 10-hydroxycamptothecin (HCPT) and monomethoxypoly(ethylene glycol) 2000 (mPEG 2000). And then one type of novel biodegradable nanoparticles, the solid dispersion (HCPT/mPEG-CHO) grafted with carboxymethylchitosan (HCPT/mPEG-g-CMCTS) was synthesized. The increase in HCPT solubility of solid dispersion was up to 21-fold compared with the original drug. With the increasing of the amount of mPEG-CHO, solubility of HCPT was from 7.71 μg/mL to 25.82 μg/mL. Colloid systems based on solid dispersion were stable in aqueous medium at 5°C. After 5 months storage at 25°C, the solid dispersions do not change at all. HCPT/mPEG-g-CMCTS was synthesized by grafting reaction of carboxymethylchitosan with mPEG-CHO to form Schiff base which is sensitive to acid environment. The release rate of HCPT from this conjugate in pH 5.4 was much higher than that in the environment of pH 7.4 and p H 4.5. The cumulative release percentages are 45%, 25%, and 15%, respectively. The cumulative release percentage of HCPT in conjugate was only 15% within 85 h while the original drug was up to 70% in pH 7.4, showing a significant slow-release property. This drug model can be attractive candidates as delivery biosystems in tumor therapy.

PEGylated guanidinylated polyallylamine as gene-delivery carrier

A novel cationic co-polymer was developed by grafting poly(ethylene glycol) (PEG) on guanidinylated polyallylamine (PAA) for gene delivery. Characterization of PEG-g-guanidinylated PAA/DNA complexes demonstrated that particle size increased and surface charge decreased with increasing the amount of PEG. The results of cytotoxicity assay proved that grafted PEG could effectively decrease the cytotoxicity of the complexes. In transfection efficiency assay, HeLa cells treated with PEG(2)-g-guanidinylated PAA (formed with 17.5 μmol guanidinylated PAA and 2 μmol PEG)/DNA (0.2 μg EGFP plasmid) complexes showed a very high level of EGFP expression. In conclusion, combination of guanidinylation and PEGylation could effectively decrease the cytotoxicity and significantly increase the transfection efficiency of PAA.

Application of spectroscopic methods for structural analysis of chitin and chitosan

Chitin, the second most important natural polymer in the world, and its N-deacetylated derivative chitosan, have been identified as versatile biopolymers for a broad range of applications in medicine, agriculture and the food industry. Two of the main reasons for this are firstly the unique chemical, physicochemical and biological properties of chitin and chitosan, and secondly the unlimited supply of raw materials for their production. These polymers exhibit widely differing physicochemical properties depending on the chitin source and the conditions of chitosan production. The presence of reactive functional groups as well as the polysaccharide nature of these biopolymers enables them to undergo diverse chemical modifications. A complete chemical and physicochemical characterization of chitin, chitosan and their derivatives is not possible without using spectroscopic techniques. This review focuses on the application of spectroscopic methods for the structural analysis of these compounds.

Self-assembled particles of N-phthaloylchitosan-g-polycaprolactone molecular bottle brushes as carriers for controlled release of indometacin

A series of amphiphilic N-phthaloylchitosan-g-polycaprolactone molecular bottle brushes were prepared by "graft onto" method. The narrow distribution of polycaprolactone macromonomers ensures that the molecular bottle brushes can self-assemble into highly monodisperse particles, which have the ability to get a high loading efficiency of the hydrophobic drug, indometacin (INN). Searching for the effective drug loading ratio, three parameters such as polycaprolactone chain length, the grafting content and concentration of the molecular bottle brushes were tested to entrap INN. These encapsulated drug particles show sustained release of the encapsulated INN, of which 91.7% was released in 22 h at 37 degrees C in phosphate buffered saline. The self-assembled particles of the molecular bottle brushes as carriers for INN can effectively prevent the drug from releasing quickly and prolong the release time, which is a promising candidate for potential clinical applications.

A nanomedicine transports a peptide caspase-3 inhibitor across the blood-brain barrier and provides neuroprotection

Caspases play an important role as mediators of cell death in acute and chronic neurological disorders. Although peptide inhibitors of caspases provide neuroprotection, they have to be administered intracerebroventricularly because they cannot cross the blood-brain barrier (BBB). Herein, we present a nanocarrier system that can transfer chitosan nanospheres loaded with N-benzyloxycarbonyl-Asp(OMe)-Glu(OMe)-Val-Asp(OMe)-fluoromethyl ketone (Z-DEVD-FMK), a relatively specific caspase-3 inhibitor, across BBB. Caspase-3 was chosen as a pharmacological target because of its central role in cell death. Polyethylene glycol-coated nanospheres were conjugated to an anti-mouse transferrin receptor monoclonal antibody (TfRMAb) that selectively recognizes the TfR type 1 on the cerebral vasculature. We demonstrate with intravital microscopy that this nanomedicine is rapidly transported across the BBB without being measurably taken up by liver and spleen. Pre- or post-treatment (2 h) with intravenously injected Z-DEVD-FMK-loaded nanospheres dose dependently decreased the infarct volume, neurological deficit, and ischemia-induced caspase-3 activity in mice subjected to 2 h of MCA occlusion and 24 h of reperfusion, suggesting that they released an amount of peptide sufficient to inhibit caspase activity. Similarly, nanospheres inhibited physiological caspase-3 activity during development in the neonatal mouse cerebellum on postnatal day 17 after closure of the BBB. Neither nanospheres functionalized with TfRMAb but not loaded with Z-DEVD-FMK nor nanospheres lacking TfRMAb but loaded with Z-DEVD-FMK had any effect on either paradigm, suggesting that inhibition of caspase activity and subsequent neuroprotection were due to efficient penetration of the peptide into brain. Thus, chitosan nanospheres open new and exciting opportunities for brain delivery of biologically active peptides that are useful for the treatment of CNS disorders.

Surpassing the use of copper in the click functionalization of polymeric nanostructures: a strain-promoted approach

The limitations (depolymerization and Cu contamination) in the use of Cu(I)-catalyzed azide-alkyne [3 + 2] cycloadditions (CuAAC) for the selective click functionalization of polysaccharide-based systems have been efficiently surpassed using a strain-promoted approach (SPAAC). The SPAAC decoration of chitosan-g-poly(ethylene glycol) nanostructures with an immunoglobulin G under physiological conditions represents a step forward in the preparation of immunonanoparticles.

Targeted delivery with peptidomimetic conjugated self-assembled nanoparticles

Peptides produce specific nanostructures, making them useful for targeting in biological systems but they have low bioavailability, potential immunogenicity and poor metabolic stability. Peptidomimetic self-assembled NPs can possess biological recognition motifs as well as providing desired engineering properties. Inorganic NPs, coated with self-assembled macromers for stability and anti-fouling, and conjugated with target-specific ligands, are advancing imaging from the anatomy-based level to the molecular level. Ligand conjugated NPs are attractive for cell-selective tumor drug delivery, since this process has high transport capacity as well as ligand dependent cell specificity. Peptidomimetic NPs can provide stronger interaction with surface receptors on tumor cells, resulting in higher uptake and reduced drug resistance. Self-assembled NPs conjugated with peptidomimetic antigens are ideal for sustained presentation of vaccine antigens to dendritic cells and subsequent activation of T cell mediated adaptive immune response. Self-assembled NPs are a viable alternative to encapsulation for sustained delivery of proteins in tissue engineering. Cell penetrating peptides conjugated to NPs are used as intracellular delivery vectors for gene expression and as transfection agents for plasmid delivery. In this work, synthesis, characterization, properties, immunogenicity, and medical applications of peptidomimetic NPs in imaging, tumor delivery, vaccination, tissue engineering, and intracellular delivery are reviewed.