Bioconjugation of laminin peptide YIGSR with poly(styrene co-maleic acid) increases its antimetastatic effect on lung metastasis of B16-BL6 melanoma cells

Recent Advances in Formulations for Long-Acting Delivery of Therapeutic Peptides

Recent preclinical and clinical studies have focused on the active area of therapeutic peptides due to their high potency, selectivity, and specificity in treating a broad range of diseases. However, therapeutic peptides suffer from multiple disadvantages, such as limited oral bioavailability, short half-life, rapid clearance from the body, and susceptibility to physiological conditions (e.g., acidic pH and enzymolysis). Therefore, high peptide dosages and dose frequencies are required for effective patient treatment. Recent innovations in pharmaceutical formulations have substantially improved therapeutic peptide administration by providing the following advantages: long-acting delivery, precise dose administration, retention of biological activity, and improvement of patient compliance. This review discusses therapeutic peptides and challenges in their delivery and explores recent peptide delivery formulations, including micro/nanoparticles (based on lipids, polymers, porous silicon, silica, and stimuli-responsive materials), (stimuli-responsive) hydrogels, particle/hydrogel composites, and (natural or synthetic) scaffolds. This review further covers the applications of these formulations for prolonged delivery and sustained release of therapeutic peptides and their impact on peptide bioactivity, loading efficiency, and (in vitro/in vivo) release parameters.

Enhanced gene transfection efficiency by use of peptide vectors containing laminin receptor-targeting sequence YIGSR

This study presents the design and evaluation of a series of multifunctional peptides and their gene delivery abilities. The peptide sequences contained a cell-penetrating segment, six continuous histidine residues, a stearyl moiety and a laminin receptor-targeting segment. The YIGSR segment promoted cellular uptake through the interaction with laminin receptors on the surface of cells, which resulted in a great improvement in gene transfection efficiency. The conformation, particle size and zeta potential of peptide/DNA complexes were characterized via circular dichroism and dynamic light scattering. Their gene transfection efficiency was investigated by fluorescence-activated cell sorting and confocal microscopy. The transfection efficiency of the designed peptide vectors was higher than that of Lipo 2000. The peptide TAT-H₆-K(C₁₈)-YIGSR displayed transfection efficiencies at N/P ratios of 6, which was 3.5 and 7 times higher than that of Lipo 2000 in B16F10 and 293T cells, respectively. All peptides exhibited lower cytotoxicity than Lipo 2000 in B16F10 and 293T cells. In summary, the designed YIGSR-containing multifunctional peptide gene vectors promoted cellular uptake and gene transfection. Their in vivo transfection ability was investigated in zebrafish, and the transfection efficiency was determined by confocal microscopy and bioluminescence imaging. The peptide vectors, owing to their relatively short sequences and ease of functionalization, offer a promising approach for gene delivery because of their low cytotoxicity and high transfection efficiency.

Modifying styrene-maleic acid co-polymer for studying lipid nanodiscs

Recently, styrene-maleic acid copolymer lipid nanodiscs have become an increasingly popular tool for the study of membrane proteins. In the work we report here, we have developed a novel method for the efficient preparation of labeled nanodiscs, under chemically mild conditions, by modification of the hydrolyzed styrene-maleic acid copolymer. This protocol is designed to be easily accessible to biochemistry laboratories. We use this procedure to prepare various fluorescent nanodiscs labeled with different fluorophores. By studying the development of Förster resonance energy transfer, we demonstrate the rapid exchange of co-polymer between nanodiscs. This demonstration, in conjunction of previous work, indicates that the lipid nanodiscs prepared using this polymer are very dynamic structures with rapid exchange of the different components.

Dual-Color-Emitting Carbon Nanodots for Multicolor Bioimaging and Optogenetic Control of Ion Channels

The development of intrinsically multicolor-emitting carbon nanodots (CNDs) has been one of the great challenges for their various fields of applications. Here, the controlled electronic structure engineering of CNDs is performed to emit two distinct colors via the facile surface modification with 4-octyloxyaniline. The so-called dual-color-emitting CNDs (DC-CNDs) can be stably encapsulated within poly(styrene-co-maleic anhydride) (PSMA). The prepared water-soluble DC-CNDs@PSMA can be successfully applied to in vitro and in vivo dual-color bioimaging and optogenetics. In vivo optical imaging can visualize the biodistribution of intravenously injected DC-CNDs@PSMA. In addition, the light-triggered activation of ion channel, channelrhodopsin-2, for optogenetic applications is demonstrated. As a new type of fluorophore, DC-CNDs offer a big insight into the design of charge-transfer complexes for various optical and biomedical applications.

Polymer-Based Prodrugs: Improving Tumor Targeting and the Solubility of Small Molecule Drugs in Cancer Therapy

The majority of anticancer drugs have poor aqueous solubility, produce adverse effects in healthy tissue, and thus impose major limitations on both clinical efficacy and therapeutic safety of cancer chemotherapy. To help circumvent problems associated with solubility, most cancer drugs are now formulated with co-solubilizers. However, these agents often also introduce severe side effects, thereby restricting effective treatment and patient quality of life. A promising approach to addressing problems in anticancer drug solubility and selectivity is their conjugation with polymeric carriers to form polymer-based prodrugs. These polymer-based prodrugs are macromolecular carriers, designed to increase the aqueous solubility of antitumor drugs, can enhance bioavailability. Additionally, polymer-based prodrugs approach exploits unique features of tumor physiology to passively facilitate intratumoral accumulation, and so improve chemodrug pharmacokinetics and pharmacological properties. This review introduces basic concepts of polymer-based prodrugs, provides an overview of currently emerging synthetic, natural, and genetically engineered polymers that now deliver anticancer drugs in preclinical or clinical trials, and highlights their major anticipated applications in anticancer therapies.

Polymer-based vehicles for therapeutic peptide delivery

During the last decades increasing attention has been paid to peptides as potential therapeutics. However, clinical applications of peptide drugs suffer from susceptibility to degradation, rather short circulation half-life, limited ability to cross physiological barriers and potential immunogenicity. These challenges can be addressed by using polymeric materials as peptide delivery systems, owing to their versatile structures and properties. A number of polymer-based vehicles have been developed to stabilize the peptides and to control their release rates. Unfortunately, no single polymer or formulation strategy has been considered ideal for all types of peptide drugs. In this review, currently used and potential polymer-based systems for the peptide delivery will be discussed.

Synthesis and evaluation of cationically modified poly(styrene-alt-maleic anhydride) nanocarriers for intracellular gene delivery

The paper discusses the intracellular gene delivery efficacy of various cationic PSMA derivatives.

Brain delivery of proteins via their fatty acid and block copolymer modifications

It is well known that hydrophobic small molecules penetrate cell membranes better than hydrophilic molecules. Amphiphilic molecules that dissolve both in lipid and aqueous phases are best suited for membrane transport. Transport of biomacromolecules across physiological barriers, e.g. the blood-brain barrier, is greatly complicated by the unique structure and function of such barriers. Two decades ago we adopted a simple philosophy that to increase protein delivery to the brain one needs to modify this protein with hydrophobic moieties. With this general idea we began modifying proteins (antibodies, enzymes, hormones, etc.) with either hydrophobic fatty acid residues or amphiphilic block copolymer moieties, such as poy(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) (pluronics or poloxamers) and more recently, poly(2-oxasolines). This simple approach has resulted in impressive successes in CNS drug delivery. We present a retrospective overview of these works initiated in the Soviet Union in 1980s, and then continued in the United States and other countries. Notably some of the early findings were later corroborated by brain pharmacokinetic data. Industrial development of several drug candidates employing these strategies has followed. Overall modification by hydrophobic fatty acids residues or amphiphilic block copolymers represents a promising and relatively safe strategy to deliver proteins to the brain.

Amphiphilic graft copolymer based on poly(styrene-co-maleic anhydride) with low molecular weight polyethylenimine for efficient gene delivery

Background and methods

A new amphiphilic comb-shaped copolymer (SP) was synthesized by conjugating poly(styrene-co-maleic anhydride) with low molecular weight polyethyleneimine for gene delivery. Fourier transform infrared spectrum, ¹H nuclear magnetic resonance, and gel permeation chromatography were used to characterize the graft copolymer.

Results

The buffering capability of SP was similar to that of polyethyleneimine within the endosomal pH range. The copolymer could condense DNA effectively to form complexes with a positive charge (13–30 mV) and a small particle size (130–200 nm) at N/P ratios between 5 and 20, and protect DNA from degradation by DNase I. In addition, SP showed much lower cytotoxicity than polyethyleneimine 25,000. Importantly, the gene transfection activity and cellular uptake of SP-DNA complexes were all markedly higher than that of complexes of polyethyleneimine 25,000 and DNA in MCF-7 and MCF-7/ADR cell lines.

Conclusion

This work highlights the promise of SP as a safe and efficient synthetic vector for DNA delivery.

Anti-angiogenic peptides for cancer therapeutics

Peptides have emerged as important therapeutics that are being rigorously tested in angiogenesis-dependent diseases due to their low toxicity and high specificity. Since the discovery of endogenous proteins and protein fragments that inhibit microvessel formation (thrombospondin, endostatin) several peptides have shown promise in pre-clinical and clinical studies for cancer. Peptides have been derived from thrombospondin, collagens, chemokines, coagulation cascade proteins, growth factors, and other classes of proteins and target different receptors. Here we survey recent developments for anti-angiogenic peptides with length not exceeding 50 amino acid residues that have shown activity in pre-clinical models of cancer or have been tested in clinical trials; some of the peptides have been modified and optimized, e.g., through L-to-D and non-natural amino acid substitutions. We highlight technological advances in peptide discovery and optimization including computational and bioinformatics tools and novel experimental techniques.

EILDV-conjugated, etoposide-loaded biodegradable polymeric micelles directing to tumor metastatic cells overexpressing α4β1 integrin

In the present study, poly(ethylene glycol)-b-poly(ε-caprolactone) micelles loaded with etoposide (ETO) were formulated and further conjugated with pentapeptide Glu-Ile-Leu-Asp-Val (EILDV) to target α4β1 integrin receptor overexpressed on metastatic tumor cell. Using a distinct ratio of carboxyl-terminated poly(ethylene glycol)-block-poly(ε-caprolactone) (HOOC-PEG-b-PCL) to methoxy-poly(ethylene glycol)-block-poly(ε-caprolactone (CH₃O-PEG-b-PCL) polymers, we formulated a series of micellar formulations having different surface densities of EILDV and observed optimum cellular uptake of micelles with 10% EILDV surface density by B16F10 cells. The cytotoxicity of EILDV-conjugated micelles was observed close to 1.5-fold higher than plain ETO after 72 h of drug incubation, demonstrating controlled release of drug inside the cell after enhanced intracellular uptake with the ability to selectively target cancer cells. In addition, EILDV-conjugated micelles inhibited the migration of B16F10 cells effectively compared with plain ETO and non-conjugated micellar formulations when cells were treated with equivalent cytotoxic concentration of the drug, i.e., IC₂₅. B16F10 cells treated with EILDV-conjugated micelles showed a significant reduction in the attachment of cells to the substrate-coated plate compared with non-conjugated micellar formulations, implying retention of the biological activity of EILDV after coupling to micelles. Furthermore, the in vivo experimental metastasis assay conducted on C57BL/6 mice demonstrated significant activity of EIDLV-conjugated micelles in the reduction of pulmonary metastatic nodule formation in both pretreatment and post-treatment methods. In conclusion, EIDLV-conjugated micelles showed higher efficacy in the treatment of metastasis and would be a promising approach in the treatment of metastasis.

Current trends in liposome research

Among the several drug delivery systems, liposomes--phospholipid nanosized vesicles with a bilayered membrane structure--have drawn a lot of interest as advanced and versatile pharmaceutical carriers for both low and high molecular weight pharmaceuticals. At present, liposomal formulations span multiple areas, from clinical application of the liposomal drugs to the development of various multifunctional liposomal systems to be used in therapy and diagnostics. This chapter provides a brief overview of various liposomal products currently under development at experimental and preclinical level.

Inhibition of ovarian cancer cell metastasis by a fusion polypeptide Tat-ELP

Tumor cell metastasis is a complex, multi-step process that is a major cause of death and morbidity amongst cancer patients. Cell adhesion plays a critical role in the development of metastatic cancer, and it is mediated by interactions between receptors on the cell surface and ligands of the extracellular matrix or other surfaces. Therefore, inhibition of the cell adhesion process appears to be an effective method of preventing metastasis. This work describes a genetically engineered polypeptide with the potential to prevent cell adhesion and inhibit metastasis. We have found that the cell penetrating peptide Tat, fused with elastin-like polypeptide (ELP) inhibited adhesion, spreading, invasion and migration of SKOV-3 ovarian cancer cells in cell culture. Furthermore, we have also confirmed that Tat-ELP has anti-metastatic potential in an experimental ovarian cancer metastasis model in vivo, causing approximately 80% reduction in the tumor burden. Since cell attachment is an important step in tumor cell invasion and metastasis, these results suggest a novel role of Tat-ELP as a therapeutic intervention in cancer metastasis.

CNS drug delivery: opioid peptides and the blood-brain barrier

Peptides are key regulators in cellular and intercellular physiological responses and possess enormous promise for the treatment of pathological conditions. Opioid peptide activity within the central nervous system (CNS) is of particular interest for the treatment of pain owing to the elevated potency of peptides and the centrally mediated actions of pain processes. Despite this potential, peptides have seen limited use as clinically viable drugs for the treatment of pain. Reasons for the limited use are primarily based in the physiochemical and biochemical nature of peptides. Numerous approaches have been devised in an attempt to improve peptide drug delivery to the brain, with variable results. This review describes different approaches to peptide design/modification and provides examples of the value of these strategies to CNS delivery of peptide drugs. The various modes of modification of therapeutic peptides may be amalgamated, creating more efficacious "hybrid" peptides, with synergistic delivery to the CNS. The ongoing development of these strategies provides promise that peptide drugs may be useful for the treatment of pain and other neurologically-based disease states in the future.

Nanoparticle formation from poly(acrylic acid) and oppositely charged peptides

Cationic peptides self assemble upon interacting with sodium salt of oppositely charged polymer, poly(acrylic acid), PAA, giving rise to water-soluble nanoparticles at very low concentration (0.1 mM of PAA). The morphology of these kinds of nanoparticles is mainly governed by the composition of the complexes, which can be expressed as Z+/-, i.e., the ratio of positively charged units to the concentration of anionic units of the polymers present in the system. In the present study, at lower Z+/-, the particles are elongated in shape but adopt spherical shape of 75-100 nm in diameter at higher Z+/- values. We propose that the nanoparticles containing cationic peptides obtained by this methodology can serve as delivery system to enhance the antinociception effect of the chimeric peptide with previously administered doses.

Control of melanoma progression by various matrikines from basement membrane macromolecules

Many biological processes such as cell differentiation, cell migration or gene expression are tightly controlled by cell-cell interactions or by various cytokines. During tumor progression, cancer cells are in contact with extracellular matrix (ECM) macromolecules involving specific receptors such as integrins. The different stages of tumor progression, and mainly the proteolytic cascades implicated in extracellular matrix degradation and cell migration, may be controlled by the extracellular matrix macromolecules or by domains released by directed and limited proteolysis of these molecules. In this review, we summarise the biological effects of various peptides, named matrikines, derived from basement membranes (BM) components, such as laminins (LN), proteoglycans or collagens. These peptides may control tumor progression by regulating the proteolytic cascades leading to cancer cell dissemination and metastasis.

[DDS and Me]

With the success of the human genome project, the focus of life science research has shifted to the functional and structural analyses of proteins, such as proteomics and structural genomics. These analyses of proteins including newly identified proteins are expected to contribute to the identification of therapeutically applicable proteins for various diseases. Thus, pharmaco-proteomic-based drug discovery and development for protein therapies, including gene therapy, cell therapy, and vaccine therapy, is attracting current attention. However, there is clinical difficulty in using almost all bioactive proteins, because of their very low stability and pleiotropic actions in vivo. To promote pharmaco-proteomic-based drug discovery and development, we have attempted to develop drug delivery systems (DDSs), such as the protein-drug innovation system and the optimal cell therapeutic system. In this review, we introduce our original DDSs.

Photo-control of the interaction between endothelial cells and photo-cation generatable water-soluble polymers

In this study photo-control of the non-biospecific interaction between endothelial cell membranes and photo-cation generatable water-soluble polymers were examined. The water-soluble polymers contained triphenylmethane leucohydroxide (malachite green) groups (contents: 0.4 and 1.6 mol%), which dissociate into triphenylmethyl cations and counter hydroxide ions upon ultraviolet light (UV) irradiation, and were prepared by free radical copolymerization of diphenyl(4-vinylphenyl)methane leucohydroxide and acrylamide. The nature and magnitude of the interaction was quantitatively assessed by direct luminescence measurement of the intracellular calcium ion concentration using a calcium-sensitive photoprotein, aequorin. When a PBS buffer of the photoreactive copolymers were added, prior to UV irradiation, to a PBS suspension of cultured bovine endothelial cells loaded with aequorin, no detectable elevation of Ca(2+) was measured. In contrast, cationic copolymers, derived from the photoreactive copolymers after UV irradiation at a wavelength of 290<lambda<410 nm, induced an immediate transient increase in the cytosolic free Ca(2+) concentration due to a Ca(2+) inflow from the extracellular space into the cells, which may be due to non-biospecific transmembrane stimulation. Longer UV irradiation exposures of the copolymers and higher concentrations of the polymers, with higher contents of the photodissociable group, resulted in more Ca(2+) inflow with little cellular damage. The photo-cation generatable copolymers developed here made possible to control the non-biospecific interaction with endothelial cell membranes by UV irradiation condition, and composition and amount of the copolymer.

Peptide and protein drug delivery to and into tumors: challenges and solutions

The potential of peptide and protein anticancer agents has yet to be realized owing to the many unresolved problems concerning their delivery to the site of a tumor and into tumor cells. However, our understanding of the mechanisms underlying the biological fate and biodistribution of protein and peptide drugs has advanced to the stage where methods that use or influence these mechanisms are now available. There are different approaches that can improve the stability, longevity and targeting of peptides and proteins in the body, such as their modification with various soluble polymers, incorporation into microparticular drug carriers, enhanced permeability and retention effect-based tumor targeting and the use of targeting moieties. Furthermore, new approaches to intracellular drug delivery, including the use of transduction proteins and peptides, are being developed. These advances promise the delivery of a new generation of anticancer drugs.

Synthesis and characterization of a novel glycopolymer with protective activity toward human anti-alpha-Gal antibodies

An efficient and rapid synthesis of the derivative of the biocompatible polymer poly(styrene co-maleic acid) with Linear B disaccharide (Galili antigen) was achieved. The oligosaccharide portion was obtained by a transglycosylation reaction catalyzed by coffee bean alpha-D-galactosidase using p-nitrophenyl-alpha-D-galactopyranoside both as donor and as acceptor. The reaction was carried out in aqueous buffer without any organic cosolvent. The molar yield (30%) and the regioselectivity (82%) were significantly improved with respect to the data so far reported in the literature. The selective reduction of the p-nitrophenyl group afforded the p-aminophenyl derivative of Linear B disaccharide. Linkage of this derivative via an amidic bond to the poly(styrene co-maleic acid) was obtained by using N'-(3-dimethylaminopropyl)-N-ethylcarbodiimide hydrochloride and N-hydroxysuccinimide. The products were chemically characterized by ionspray mass spectrometry, infrared, (13)C- and (1)H-nuclear magnetic resonance. The glycopolymer specifically reacts with human serum containing antibodies and with a mixture of partially purified human IgG and IgM anti-Linear B. It efficiently protects pig kidney PK15 cells from cytotoxic effects of human serum.

Peptide drug modifications to enhance bioavailability and blood-brain barrier permeability

Peptides have the potential to be potent pharmaceutical agents for the treatment of many central nervous system derived maladies. Unfortunately peptides are generally water-soluble compounds that will not enter the central nervous system, via passive diffusion, due to the existence of the blood-brain barrier. Peptides can also undergo metabolic deactivation by peptidases, thus further reducing their therapeutic benefits. In targeting peptides to the central nervous system consideration must be focused both on increasing bioavailability and enhancing brain uptake. To date multiple strategies have been examined with this focus. However, each strategy comes with its own complications and considerations. In this review we assess the strengths and weaknesses of many of the methods currently being examined to enhance peptide entry into the central nervous system.

Bioconjugation of laminin-related peptide YIGSR with polyvinyl pyrrolidone increases its antimetastatic effect due to a longer plasma half-life

Polyvinyl pyrrolidone (PVP) which can be radically synthesized and have a long blood residency was used to modify the laminin-related peptide YIGSR, and its inhibitory effect on experimental lung metastasis of B16-BL6 melanoma cells was examined. The antimetastatic effect of PVP-conjugated YIGSR (PVP-YIGSR) was more than 100-fold greater than that of native YIGSR. When injected intravenously, PVP-YIGSR showed more than a 15-fold longer plasma half-life relative to native YIGSR. In addition, the stability of YIGSR in plasma was increased by conjugation with PVP. These findings suggest that PVP is a useful polymeric modifier for increasing the antimetastatic activity of YIGSR.