A Biocompatible Arginine-based Polycation

A rapid-floating natural polysaccharide gel-raft with double-effect for the treatment of gastroesophageal reflux disease

Gastroesophageal reflux disease (GERD) is a prevalent gastrointestinal condition characterized by regurgitating stomach contents into the esophagus, causing mucosal damage or erosion. Clinical physical protection treatment mainly relies on the use of floating rafts. Bletilla striata (BS) is widely regarded as the first-choice drug for treating digestive tract injuries in Chinese Medicine. The rapid-floating gel-raft (B-R) was prepared via a one-step swelling method using natural BS polysaccharide and glyceryl monooleate. Panax notoginseng saponins (PNS) were loaded to further prepare P/B-R according to clinical experience. Possessing hydrophobic dense, stratified porous structure and stable rheological properties, an outperforming floating performance of P/B-R was proven compared with Gaviscon® (alginate-antacid formulation) in vitro. In vivo imaging results showed that P/B-R can retain and adhere to the gastric mucosa of rats for up to 90 min, protecting and repairing the mucosa. Besides physical protection in situ, the systemic effects of antioxidant and anti-inflammatory actions for treating GERD were achieved through the intestinal release of PNS. Acid-labile PNS was protected by P/B-R against gastric acid, attaining the desired release and permeability. A significantly effective mucosa injury protective effect of P/B-R was found in ethanol-induced gastric damage model on rats. Moreover, P/B-R exhibits excellent biosafety at the cellular level.

Nanosystems for gene therapy targeting brain damage caused by viral infections

Several human pathogens can cause long-lasting neurological damage. Despite the increasing clinical knowledge about these conditions, most still lack efficient therapeutic interventions. Gene therapy (GT) approaches comprise strategies to modify or adjust the expression or function of a gene, thus providing therapy for human diseases. Since recombinant nucleic acids used in GT have physicochemical limitations and can fail to reach the desired tissue, viral and non-viral vectors are applied to mediate gene delivery. Although viral vectors are associated to high levels of transfection, non-viral vectors are safer and have been further explored. Different types of nanosystems consisting of lipids, polymeric and inorganic materials are applied as non-viral vectors. In this review, we discuss potential targets for GT intervention in order to prevent neurological damage associated to infectious diseases as well as the role of nanosized non-viral vectors as agents to help the selective delivery of these gene-modifying molecules. Application of non-viral vectors for delivery of GT effectors comprise a promising alternative to treat brain inflammation induced by viral infections.

A bio-inspired fluorescent nano-injectable hydrogel as a synergistic drug delivery system

A nano-injectable hydrogel with fluorescence properties and controlled sequential release of dual drugs.

Recent Progress in Ionic Coassembly of Cationic Peptides and Anionic Species

Peptide assembly has been extensively exploited as a promising platform for the creation of hierarchical nanostructures and tailor-made bioactive materials. Ionic coassembly of cationic peptides and anionic species is paving the way to provide particularly important contribution to this topic. In this review, the recent progress of ionic coassembly soft materials derived from the electrostatic coupling between cationic peptides and anionic species in aqueous solution is systematically summarized. The presentation of this review starts from a brief background on the general importance and advantages of peptide-based ionic coassembly. After that, diverse combinations of cationic peptides with small anions, macro- and/or oligo-anions, anionic polymers, and inorganic polyoxometalates are described. Emphasis is placed on the hierarchical structures, value-added properties, and applications. The molecular design of cationic peptides and the general principles behind the ionic coassembled structures are discussed. It is summarized that the combination of interesting and unique characteristics that arise both from the chemical diversity of peptides and the wide range of anionic species may contribute in a variety of output, including drug delivery, tissue engineering, gene transfection, and antibacterial activity. The emergent new phenomena and findings are illustrated. Finally, the outlook for the peptide-based ionic coassembly systems is also presented.

Single injection of IL-12 coacervate as an effective therapy against B16-F10 melanoma in mice

Melanoma is the deadliest type of skin cancer with one of the fastest increasing incidence rates among solid tumors. The use of checkpoint inhibitors (e.g. αPD-1 antibody) has recently emerged as a viable alternative to conventional modes of therapy. However, increasing evidence points towards the need for a tumor priming step to improve intratumoral immune cell infiltration. IL-12 is an immune-activating cytokine with such potential and was explored in earlier clinical trials as a highly concentrated systemic infusion. This unfortunately led to severe adverse effects. From this perspective, the localization and gradual release of such a potent immunotherapeutic agent in the tumor microenvironment is desired. This manuscript reports the use of a heparin-based complex coacervate to deliver IL-12, in which heparin-binding motifs on IL-12 allow for its effective encapsulation. IL-12-encapsulated complex coacervates significantly improved the bioactivity of IL-12 and provided protection from proteolytic cleavage in-vitro. Indeed, a single injection of IL-12 coacervate significantly inhibits the in-vivo growth of treated and untreated, contralateral tumor growth in a syngeneic B16F10 mouse melanoma model. Furthermore, tumors in mice receiving IL-12 complex coacervate treatment displayed increased infiltration by natural killer (NK) cells and CD8α+ T cells, and a decreased presence of CD4+Foxp3+ regulatory T cells. This study provides proof-of-concept data supporting the use of complex coacervates for sustained delivery of immunostimulatory proteins as an effective therapeutic strategy against disseminated tumors.

Extended Intravitreal Rabbit Eye Residence of Nanoparticles Conjugated With Cationic Arginine Peptides for Intraocular Drug Delivery: In Vivo Imaging

Purpose

Drug delivery by intravitreal injection remains problematic, small agents and macromolecules both clearing rapidly. Typical carriers use microparticles (>2 μm), with size-related liabilities, to slow diffusion. We recently described cationic nanoparticles (NP) where conjugated Arg peptides prolonged residence in rat eyes, through ionic interaction with vitreal poly-anions. Here we extended this strategy to in vivo tracking of NP-conjugate (NPC) clearance from rabbit eyes. Relating t_1/2 to zeta potential, and varied dose, we estimated the limits of this charge-based delivery system.

Methods

NPC carried covalently attached PEG₈-2Arg or PEG₈-3Arg pentapeptides, having known sequences from human eye proteins. Peptides were conjugated (61–64 per NPC); each NP/NPC also carried a cyanine7 tag (<0.5 dye/particle). In vivo imaging system (IVIS), after intravitreal injection, estimated NPC loss by 800-nm photon emission (745-nm excitation) at 1 to 3-week intervals following initial scan at day 10.

Results

NPC of 2Arg-peptides or 3Arg-peptides showed clearance t_1/2 of 7 days and 17 days respectively, unconjugated NP t_1/2 was <<5 days. Doses of 90, 180, and 360 μg of PEG₈-2Arg NPC were compared. The lower doses showed dose-proportional day-10 concentration, and similar clearance. Higher early loss was seen with a 360-μg dose, exceeding rabbit vitreal binding capacity. No inflammation was observed.

Conclusions

This type of cationic NPC can safely increase residence t_1/2 in a 1 to 3-week range, with dose <100 μg per mL vitreous. Human drug load may then range from 10 to 100 μg/eye, usefulness depending on individual drug potency and release rate, superimposed on extended intravitreal residence.

Macro- and Microphase Separated Protein-Polyelectrolyte Complexes: Design Parameters and Current Progress

Protein-containing polyelectrolyte complexes (PECs) are a diverse class of materials, composed of two or more oppositely charged polyelectrolytes that condense and phase separate near overall charge neutrality. Such phase-separation can take on a variety of morphologies from macrophase separated liquid condensates, to solid precipitates, to monodispersed spherical micelles. In this review, we present an overview of recent advances in protein-containing PECs, with an overall goal of defining relevant design parameters for macro- and microphase separated PECs. For both classes of PECs, the influence of protein characteristics, such as surface charge and patchiness, co-polyelectrolyte characteristics, such as charge density and structure, and overall solution characteristics, such as salt concentration and pH, are considered. After overall design features are established, potential applications in food processing, biosensing, drug delivery, and protein purification are discussed and recent characterization techniques for protein-containing PECs are highlighted.

Cationic graphene oxide nanoplatform mediates miR-101 delivery to promote apoptosis by regulating autophagy and stress

Introduction

MicroRNA-101 (miR-101) is an intense cancer suppressor with special algorithm to target a wide range of pathways and genes which indicates the ability to regulate apoptosis, cellular stress, metastasis, autophagy, and tumor growth. Silencing of some genes such as Stathmin1 with miR-101 can be interpreted as apoptotic accelerator and autophagy suppressor. It is hypothesized that hybrid microRNA (miRNA) delivery structures based on cationized graphene oxide (GO) could take superiority of targeting and photothermal therapy to suppress the cancer cells.

Materials and methods

In this study, GO nanoplatforms were covalently decorated with polyethylene glycol (PEG) and poly-l-arginine (P-l-Arg) that reduced the surface of GO and increased the near infrared absorption ~7.5-fold higher than nonreduced GO.

Results

The prepared nanoplatform [GO-PEG-(P-l-Arg)] showed higher miRNA payload and greater internalization and facilitated endosomal scape into the cytoplasm in comparison with GO-PEG. Furthermore, applying P-l-Arg, as a targeting agent, greatly improved the selective transfection of nanoplatform in cancer cells (MCF7, MDA-MB-231) in comparison with immortalized breast cells and fibroblast primary cells. Treating cancer cells with GO-PEG-(P-l-Arg)/miR-101 and incorporating near infrared laser irradiation induced 68% apoptosis and suppressed Stathmin1 protein.

Conclusion

The obtained results indicated that GO-PEG-(P-l-Arg) would be a suitable targeted delivery system of miR-101 transfection that could downregulate autophagy and conduct thermal stress to activate apoptotic cascades when combined with photothermal therapy.

3D-Bioprinted Osteoblast-Laden Nanocomposite Hydrogel Constructs with Induced Microenvironments Promote Cell Viability, Differentiation, and Osteogenesis both In Vitro and In Vivo

An osteoblast-laden nanocomposite hydrogel construct, based on polyethylene glycol diacrylate (PEGDA)/laponite XLG nanoclay ([Mg5.34Li0.66Si8O20(OH)4]Na0.66, clay)/hyaluronic acid sodium salt (HA) bio-inks, is developed by a two-channel 3D bioprinting method. The novel biodegradable bio-ink A, comprised of a poly(ethylene glycol) (PEG)-clay nanocomposite crosslinked hydrogel, is used to facilitate 3D-bioprinting and enables the efficient delivery of oxygen and nutrients to growing cells. HA with encapsulated primary rat osteoblasts (ROBs) is applied as bio-ink B with a view to improving cell viability, distribution uniformity, and deposition efficiency. The cell-laden PEG-clay constructs not only encapsulated osteoblasts with more than 95% viability in the short term but also exhibited excellent osteogenic ability in the long term, due to the release of bioactive ions (magnesium ions, Mg2+ and silicon ions, Si4+), which induces the suitable microenvironment to promote the differentiation of the loaded exogenous ROBs, both in vitro and in vivo. This 3D-bioprinting method holds much promise for bone tissue regeneration in terms of cell engraftment, survival, and ultimately long-term function.

A biocompatible betaine-functionalized polycation for coacervation

The aqueous nature of complex coacervates provides a biologically-relevant context for various therapeutic applications. In this sense, biological applications demand a corresponding level of biocompatibility from the polyelectrolytes that participate in complex coacervation. Continued development with naturally-occurring polyelectrolytes such as heparin and chitosan underscore such aims. Herein, we design a synthetic polycation, in which betaine is conjugated to a biodegradable polyester backbone. Betaine is a naturally-occurring methylated amino acid that is ubiquitously present in human plasma. Inspired by its vast range of benefits - including but not limited to anti-inflammation, anti-cancer, anti-bacterial, anti-oxidant, protein stabilization, and cardiovascular health - we aim to impart additional functionality to a polycation for eventual use in a complex coacervate with heparin. We report on its in vitro and in vivo biocompatibility, in vitro and in vivo effect on angiogenesis, in vitro effect on microbial growth, and ability to form complex coacervates with heparin.

Sustaining Intravitreal Residence With L-Arginine Peptide-Conjugated Nanocarriers

Purpose

Intravitreal injection of antiangiogenic agents is becoming a standard treatment for neovascular retinal diseases. Sustained release of therapeutics by injecting colloidal carriers is a promising approach to reduce the injection frequency, which reduces treatment burdens and the risk of complications on patients. Such sustained release often requires carriers to have micrometer-scale dimension that, however, can potentially promote glaucoma and inflammation. Small, polycationic particles can be immobilized in vitreous through multiple cooperative ionic interactions with hyaluronic acid of the vitreous interior, but such particles are generally toxic. Here, we synthesized and examined a biocompatible dextran-based nanocarrier (<50 nm in diameter) conjugated with cationic peptides containing L-arginine with minimal toxicity, aiming to provide sustained release of therapeutic drugs in vitreous.

Methods

We synthesized the nanocarriers with condensed cholesteryl dextran (CDEX) as core material. Cationic peptides containing 1 to 4 arginine groups, along with fluorescence tags, were conjugated to the CDEX surface. We monitored the carrier diffusion rate ex vivo and half-lives in vivo in rodent vitreous using fluorescence imaging. We evaluated the toxicity by histological examinations at the second, third, eighth, and thirty-sixth week.

Results

The diffusion rate of nanocarriers was inversely related to zeta potential values in freshly isolated vitreous humor. We observed increased half-lives in vivo with increasing zeta potential (up to 240 days). Histological examinations confirmed no adverse effects on ocular morphology and organization.

Conclusions

We demonstrated the potential of L-arginine peptide-conjugated nanocarriers toward safe and sustained therapeutic release system for posterior eye diseases.

Weak Bond-Based Injectable and Stimuli Responsive Hydrogels for Biomedical Applications

Here we define hydrogels crosslinked by weak bonds as physical hydrogels. They possess unique features including reversible bonding, shear thinning and stimuli-responsiveness. Unlike covalently crosslinked hydrogels, physical hydrogels do not require triggers to initiate chemical reactions for in situ gelation. The drug can be fully loaded in a pre-formed hydrogel for delivery with minimal cargo leakage during injection. These benefits make physical hydrogels useful as delivery vehicles for applications in biomedical engineering. This review focuses on recent advances of physical hydrogels crosslinked by weak bonds: hydrogen bonds, ionic interactions, host-guest chemistry, hydrophobic interactions, coordination bonds and π-π stacking interactions. Understanding the principles and the state of the art of gels with these dynamic bonds may give rise to breakthroughs in many biomedical research areas including drug delivery and tissue engineering.

Co-assembly of polyoxometalates and peptides towards biological applications

The synergistic self-assembly of biomolecules with polyoxometalates (POMs) has recently been considered as an effective approach to construct nano-biomaterials with diverse structures and morphologies towards applications in drug delivery, controlled release, tissue engineering scaffolds, and biomineralization, due to the unique features of the clusters in addition to many well-known inorganic nanoparticles. This review presents an overview of recent work focusing on the noncovalent co-assembly of peptides and POMs as well as their biological applications. In the co-assemblies triggered by the interaction between the components significant advantages are observed that POMs or peptides alone do not possess; examples include chiral recognition of hybrid metal oxides, the quick hydrolysis of peptides, and enhanced inhibition of Aβ aggregation. Finally, we outline a brief perspective on possible unresolved issues and future opportunities in this field.

A Material Conferring Hemocompatibility

There is a need for biomimetic materials for use in blood-contacting devices. Blood contacting surfaces maintain their patency through physico-chemical properties of a functional endothelium. A poly(carbonate-urea) urethane (PCU) is used as a base material to examine the feasibility of L-Arginine methyl ester (L-AME) functionalized material for use in implants and coatings. The study hypothesizes that L-AME, incorporated into PCU, functions as a bioactive porogen, releasing upon contact with blood to interact with endothelial nitric oxide synthase (eNOS) present in blood. Endothelial progenitor cells (EPC) were successfully cultured on L-AME functionalized material, indicating that L-AME -increases cell viability. L-AME functionalized material potentially has broad applications in blood-contacting medical devices, as well as various other applications requiring endogenous up-regulation of nitric oxide, such as wound healing. This study presents an in-vitro investigation to demonstrate the novel anti-thrombogenic properties of L-AME, when in solution and when present within a polyurethane-based polymer.

Dual physical dynamic bond-based injectable and biodegradable hydrogel for tissue regeneration

A biodegradable and injectable hydrogel was designed using dual physical dynamic bonds based on host-guest chemistry and electrostatic interactions to build up the network structure. The material was synthesized by simultaneously coupling mono-carboxylic acid terminated poly(ethylene glycol) and arginine to poly(ethylene aspartate diglyceride) to yield a mPEG-grafted poly(ethylene argininylaspartate diglyceride) (mPEG-g-PEAD). When mixing this polymer with α-cyclodextrin and a natural polyanion (heparin), the supramolecular network was formed in a quick gelation with shear thinning properties. The in vitro cytotoxicity was evaluated using primary baboon arterial smooth muscle cells (BaSMCs) and the results showed that cell membrane integrity, viability and metabolism were not compromised by this synthetic polycation at concentrations as high as 10 mg mL^-1, a 1000-fold lower toxicity than commercial PEI. The in vitro biocompatibility of the as-made hydrogel was also evaluated using BaSMCs. Neither the hydrogel nor the hydrogel components altered cell behavior in the assays. Fibroblast growth factor 2 was incorporated into the hydrogel and sustainably released at a nearly stable rate up to 16 days without initial burst release, suggesting potential applications in wound healing and ischemic tissue regeneration, among others.

A simple one-step method to prepare fluorescent carbon dots and their potential application in non-invasive glioma imaging

Fluorescent carbon dots (CD) possess impressive potential in bioimaging because of their low photobleaching, absence of optical blinking and good biocompatibility. However, their relatively short excitation/emission wavelengths restrict their application in in vivo imaging. In the present study, a kind of CD was prepared by a simple heat treatment method using glycine as the only precursor. The diameter of CD was lower than 5 nm, and the highest emission wavelength was 500 nm. However, at 600 nm, there was still a relatively strong fluorescent emission, suggesting CD could be used for in vivo imaging. Additionally, several experiments demonstrated that CD possessed good serum stability and low cytotoxicity. In vitro, CD could be taken up into C6 glioma cells in a time- and concentration-dependent manner, with both endosomes and mitochondria involved. In vivo, CD could be used for non-invasive glioma imaging because of its high accumulation in the glioma site of the brain, which was demonstrated by both in vivo imaging and ex vivo tissue imaging. Furthermore, the fluorescent distribution in tissue slices also showed CD distributed in glioma with high intensity, while with a low intensity in normal brain tissue. In conclusion, CD were prepared using a simple method with relatively long excitation and emission wavelengths and could be used for non-invasive glioma imaging.

Coacervate delivery systems for proteins and small molecule drugs

Coacervates represent an exciting new class of drug delivery vehicles, developed in the past decade as carriers of small molecule drugs and proteins. This review summarizes several well-described coacervate systems, including: i) elastin-like peptides for delivery of anticancer therapeutics; ii) heparin-based coacervates with synthetic polycations for controlled growth factor delivery; iii) carboxymethyl chitosan aggregates for oral drug delivery; iv) Mussel adhesive protein and hyaluronic acid coacervates. Coacervates present advantages in their simple assembly and easy incorporation into tissue engineering scaffolds or as adjuncts to cell therapies. They are also amenable to functionalization such as for targeting or for enhancing the bioactivity of their cargo. These new drug carriers are anticipated to have broad applications and noteworthy impact in the near future.

Lysine-based polycation:heparin coacervate for controlled protein delivery

Polycations have good potential as carriers of proteins and genetic material. However, poor control over the release rate and safety issues currently limit their use as delivery vehicles. Here we introduce a new lysine-based polycation, poly(ethylene lysinylaspartate diglyceride) (PELD), which exhibits high cytocompatibility. PELD self-assembles with the biological polyanion heparin into a coacervate that incorporates proteins with high loading efficiency. Coacervates of varying surface charge were obtained by simple alteration of the PELD:heparin ratio and resulted in diverse release profiles of the model protein bovine serum albumin. Therefore, coacervate charge represents a direct means of control over release rate and duration. The PELD coacervate also rapidly adsorbed onto a porous polymeric scaffold, demonstrating potential use in tissue engineering applications. This coacervate represents a safe and tunable protein delivery system for biomedical applications.

Design, synthesis, and biocompatibility of an arginine-based polyester

Polycations are very useful in biotechnology. However, most existing polycations have high toxicity that significantly limits their clinical translation. We designed poly(ethylene argininylaspartate diglyceride) (PEAD) that is based on arginine, aspartic acid, glycerol, and ethylene glycol. A set of in vitro assays demonstrated that PEAD exhibited no cytotoxicity at 1 mg/mL, which is at least 100 times higher than the widely used polycation-polyethylenimine. Subcutaneous injection of 1 mg PEAD in rats did not cause an adverse response acutely or after 4 weeks. Zeta potential measurements revealed that PEAD has high affinity to biological polyanions such as DNA and hyaluronic acid. This polycation represents a new platform of biocompatible polycations that may lead to clinical innovations in gene therapy, controlled release, tissue engineering, biosensors, and medical devices.