Shell-Sheddable Dendritic Polyglycerol Sulfates Loaded with Sunitinib for Inhibition of Tumor Angiogenesis

Induced angiogenesis, a specific hallmark of cancer, plays a vital role in tumor progression and can be targeted by inhibitors like sunitinib. Sunitinib is a small hydrophobic molecule suffering from low bioavailability and a short half-life in the bloodstream. To overcome these drawbacks, suitable drug delivery systems need to be developed. In this work dendritic polyglycerol (dPG), a well-known polymer, was functionalized with a sheddable shell. Therefore, aliphatic chains of different lengths (C₅, C₉, C₁₁) were coupled to dPG through a cleavable ester bond. To restore water solubility and improve tumor targeting, the surface was decorated with sulfate groups. The resulting shell-sheddable dPG sulfates were characterized and evaluated regarding their loading capacity and biocompatibility in cell culture. The nine-carbon chain derivative (dPG-TNS) was selected as the best candidate for further experiments due to its high drug loading capacity (20wt%), and a sustained release in vitro. The cellular biocompatibility of the blank carrier up to 1mg/mL was confirmed after 24h incubation on HeLa cells. Furthermore, the shell-cleavability of dPG-TNS under different physiological conditions was shown in a degradation study over four weeks. The activity of sunitinib-loaded dPG-TNS was demonstrated in a tube formation assay on Human umbilical vein endothelial cells (HUVECs). Our results suggest that the drug-loaded nanocarrier is a promising candidate to be further investigated in tumor treatments, as it shows similar efficacy to free sunitinib while overcoming its limitations.

Thermo-responsive injectable naringin-loaded hydrogel polymerised sodium alginate/bioglass delivery for articular cartilage

In the human body, joint cartilage is of great importance. It has long been a big therapeutic problem to fix joint cartilage lesions as it appears due to different conditions. Recent stories have shown that the cartilage replacement process must delay the extracellular (ECM) cartilage deterioration and modulate the host's inflammation response. For the reconstruction of the articular cartilage, drug-loaded injectable hydrogels were developed. This hydrogel could retain the chondrocyte phenotype, but the host's inflammatory reaction could also be controlled. The bioglass (BG)/sodium alginate (SA) injectable hydrogels was combined with agarose (AG)/Naringin hydrogel in injectable thermal response for articular cartilage regeneration with a non-chargeable hydrogel that contains both Naringin and BG (Naringin–BG hydrogels). The Naringin–BG hydrogel has an adequate swelling ratio that encourages the fusion of tissue formed with host tissue and enables the gradual release of Naringin bioavailabilities enhanced in situ. The Naringin–BG hydrogel can upgrade the typical chondrocyte phenotype by upregulating aggrecan, SRY-box 9, and collagen type II alpha one chain. It may also stimulate the polarization of M2 macrophage, lower inflammations, and prevent ECM degradations through the decrease of the expressions of the indictable metalloproteinase-13 matrix, nitric oxide synthase, and metalloproteinase-1 matrix. The formed tissues were identical to normal tissues and firmly incorporated with the surrounding tissue after administering the Naringin–BG hydrogels into the rat model articular cartilage defects. Then the injectable Naringin–BG hydrogel increases the bioavailable content of Naringin and retains the chondrocyte phenotype.

Biodegradable Dendritic Polyglycerol Sulfate for the Delivery and Tumor Accumulation of Cytostatic Anticancer Drugs

Targeted delivery and extended blood circulation of anticancer drugs have been the challenges for decreasing the adverse side effects and improving the therapeutic efficiency in cancer chemotherapy. Herein, we present a drug delivery system (DDS) based on biodegradable dendritic polyglycerol sulfate-bearing poly(caprolactone) (dPGS-PCL) chains, which has been synthesized on 20 g scale using a straightforward two-step protocol. In vivo fluorescence imaging demonstrated a significant accumulation of the DDS in the tumor environment. Sunitinib, an anticancer drug, was loaded into the DDS and the drug-induced toxicity was investigated in vitro and in vivo. The drug encapsulated in dPGS-PCL and the free drug showed similar toxicities in A431 and HT-29 cells, and the cellular uptake was comparable. The straightforward and large-scale synthesis, the organic solvent-free drug-loading approach, together with the tumor targetability of the biodegradable dendritic polyglycerols, render this copolymer a promising candidate for targeted cancer nanomedicine drug delivery systems.

Enhanced In Vitro and In Vivo Efficacy of Alginate/Silk Protein/Hyaluronic Acid with Polypeptide Microsphere Delivery for Tissue Regeneration of Articular Cartilage

Alginate/Silk fibroin/hyaluronic acid (ALG/SF/HA) nanocomposites were synthesised using blending, inter-linking, and lyophilization methods. We investigated the physicochemical properties of the resulting nanocomposites, including their water retention, weight loss, porosity and cytocompatibility. The optimum ratios of the ALG/SF/HA scaffolding were 3:6.5:0.5. Nanocomposites with optimum ratios were then prepared by integrating pilose antler polypeptides (PAPS) to poly(lactic-co-glycolic acid) (PLGA) microspheres, and the performance was investigated. PAPS-ALG/SF/HA nanocomposites exhibited desirable adhesions and proliferations. Rabbit cartilage deficiencies was developed by the animal model. The cartilage repair effects deficiencies were detected and analyzed between PAPS-SF/ALG/ALG/SF/HA, and control activity classes. The deficiencies were virtually fully remedied after 13 weeks in the presence of PAPS-ALG/SF/HA class, suggesting that the PAPS-ALG/SF/HA nanocomposites had a positive effects on joint cartilage repair.

Understanding the Interaction of Polyelectrolyte Architectures with Proteins and Biosystems

The counterions neutralizing the charges on polyelectrolytes such as DNA or heparin may dissociate in water and greatly influence the interaction of such polyelectrolytes with biomolecules, particularly proteins. In this Review we give an overview of studies on the interaction of proteins with polyelectrolytes and how this knowledge can be used for medical applications. Counterion release was identified as the main driving force for the binding of proteins to polyelectrolytes: Patches of positive charge become multivalent counterions of the polyelectrolyte and lead to the release of counterions from the polyelectrolyte and a concomitant increase in entropy. This is shown from investigations on the interaction of proteins with natural and synthetic polyelectrolytes. Special emphasis is paid to sulfated dendritic polyglycerols (dPGS). The Review demonstrates that we are moving to a better understanding of charge-charge interactions in systems of biological relevance. Research along these lines will aid and promote the design of synthetic polyelectrolytes for medical applications.

Experimental Therapeutics for the Treatment of Osteoarthritis

Osteoarthritis (OA) therapy remains a large challenge since no causative treatment options are so far available. Despite some main pathways contributing to OA are identified its pathogenesis is still rudimentary understood. A plethora of therapeutically promising agents are currently tested in experimental OA research to find an opportunity to reverse OA-associated joint damage and prevent its progression. Hence, this review aims to summarize novelly emerging experimental approaches for OA. Due to the diversity of strategies shown only main aspects could be summarized here including herbal medicines, nanoparticular compounds, growth factors, hormones, antibody-, cell- and extracellular vesicle (EV)-based approaches, optimized tools for joint viscosupplementation, genetic regulators such as si- or miRNAs and promising combinations. An abundant multitude of compounds obtained from plants, environmental, autologous or synthetic sources have been identified with anabolic, anti-inflammatory, -catabolic and anti-apoptotic properties. Some ubiquitous signaling pathways such as wingless and Integration site-1 (Wnt), Sirtuin, Toll-like receptor (TLR), mammalian target of rapamycin (mTOR), Nuclear Factor (NF)-κB and complement are involved in OA and addressed by them. Hyaluronan (HA) provided benefit in OA since many decades, and novel HA formulations have been developed now with higher HA content and long-term stability achieved by cross-linking suitable to be combined with other agents such as components from herbals or chemokines to attract regenerative cells. pH- or inflammation-sensitive nanoparticular compounds could serve as versatile slow-release systems of active compounds, for example, miRNAs. Some light has been brought into the intimate regulatory network of small RNAs in the pathogenesis of OA which might be a novel avenue for OA therapy in future. Attraction of autologous regenerative cells by chemokines and exosome-based treatment strategies could also innovate OA therapy.

Superbranched polyglycerol nanostructures as drug delivery and theranostics tools for cancer treatment

Hyperbranched polymers (HBPs), such as hyperbranched polyglycerols (HPGs) with a dendritic configuration, have been recognized for their excellent biocompatibility and multifunctionalization. HPGs have been studied for use in the delivery diagnostic, imaging and therapeutic molecules in the area of nanobiomedicine. They show superior characteristics to linear polymers and dendrimers, such as compact structure, a simple manufacturing process with easy functionalization ability, low viscosity, and high stability. Owing to these advantages, HPGs are now considered promising carriers for drug delivery, diagnostics, imaging, and theranostics applications for cancer treatment. In this review, we also discuss safety aspects of HPG-based nanoformulations in various animal models and the clinical translation status of such polymers for real-time applications.

Probing the protein corona around charged macromolecules: interpretation of isothermal titration calorimetry by binding models and computer simulations

Isothermal titration calorimetry (ITC) is a widely used tool to experimentally probe the heat signal of the formation of the protein corona around macromolecules or nanoparticles. If an appropriate binding model is applied to the ITC data, the heat of binding and the binding stoichiometry as well as the binding affinity per protein can be quantified and interpreted. However, the binding of the protein to the macromolecule is governed by complex microscopic interactions. In particular, due to the steric and electrostatic protein–protein interactions within the corona as well as cooperative, charge renormalization effects of the total complex, the application of standard (e.g., Langmuir) binding models is questionable and the development of more appropriate binding models is very challenging. Here, we discuss recent developments in the interpretation of the Langmuir model applied to ITC data of protein corona formation, exemplified for the well-defined case of lysozyme coating highly charged dendritic polyglycerol sulfate (dPGS), and demonstrate that meaningful data can be extracted from the fits if properly analyzed. As we show, this is particular useful for the interpretation of ITC data by molecular computer simulations where binding affinities can be calculated but it is often not clear how to consistently compare them with the ITC data. Moreover, we discuss the connection of Langmuir models to continuum binding models (where no discrete binding sites have to be assumed) and their possible extensions toward the inclusion of leading order cooperative electrostatic effects.

Dendritic Polyglycerol Sulfate for Therapy and Diagnostics

Dendritic polyglycerol sulfate (dPGS) has originally been investigated as an anticoagulant to potentially substitute for the natural glycosaminoglycan heparin. Compared to unfractionated heparin, dPGS possesses lower anticoagulant activity but a much higher anticomplementary effect. Since coagulation, complement activation, and inflammation are often present in the pathophysiology of numerous diseases, dPGS polymers with both anticoagulant and anticomplementary activities represent promising candidates for the development of polymeric drugs of nanosized architecture. In this review, we describe the nanomedical applications of dPGS based on its anti-inflammatory activity. Furthermore, the application of dPGS as a carrier molecule for diagnostic molecules and therapeutic drugs is reviewed, based on the ability to target tumors and localize in tumor cells. Finally, the application of dPGS for inhibition of virus infections is described.

Counterion-Release Entropy Governs the Inhibition of Serum Proteins by Polyelectrolyte Drugs

Dendritic polyelectrolytes constitute high potential drugs and carrier systems for biomedical purposes. Still, their biomolecular interaction modes, in particular those determining the binding affinity to proteins, have not been rationalized. We study the interaction of the drug candidate dendritic polyglycerol sulfate (dPGS) with serum proteins using isothermal titration calorimetry (ITC) interpreted and complemented with molecular computer simulations. Lysozyme is first studied as a well-defined model protein to verify theoretical concepts, which are then applied to the important cell adhesion protein family of selectins. We demonstrate that the driving force of the strong complexation, leading to a distinct protein corona, originates mainly from the release of only a few condensed counterions from the dPGS upon binding. The binding constant shows a surprisingly weak dependence on dPGS size (and bare charge) which can be understood by colloidal charge-renormalization effects and by the fact that the magnitude of the dominating counterion-release mechanism almost exclusively depends on the interfacial charge structure of the protein-specific binding patch. Our findings explain the high selectivity of P- and L-selectins over E-selectin for dPGS to act as a highly anti-inflammatory drug. The entire analysis demonstrates that the interaction of proteins with charged polymeric drugs can be predicted by simulations with unprecedented accuracy. Thus, our results open new perspectives for the rational design of charged polymeric drugs and carrier systems.