A colourimetric method for the determination of the degree of chemical cross-linking in aspartic acid-based polymer gels

Fabrication of deferasirox-decorated aptamer-targeted superparamagnetic iron oxide nanoparticles (SPION) as a therapeutic and magnetic resonance imaging agent in cancer therapy

In the current study, the synthesis of a theranostic platform composed of superparamagnetic iron oxide nanoparticles (SPION)-deferasirox conjugates targeted with AS1411 DNA aptamer was reported. In this regard, SPION was amine-functionalized by (3-aminopropyl)trimethoxysilane (ATPMS), and then deferasirox was covalently conjugated onto its surface. Finally, to provide guided drug delivery to cancerous tissue, AS1411 aptamer was conjugated to the complex of SPION-deferasirox. The cellular toxicity assay on CHO, C-26 and AGS cell lines verified higher cellular toxicity of targeted complex in comparison with non-targeted one. The evaluation of in vivo tumor growth inhibitory effect in C26 tumor-bearing mice illustrated that the aptamer-targeted complex significantly enhanced the therapeutic outcome in comparison with both non-targeted complex and free drug. The diagnostic capability of the prepared platform was also evaluated implementing C26-tumor-bearing mice. Obtained data confirmed higher tumor accumulation and higher tumor residence time for targeted complex through MRI imaging due to the existence of SPION as a contrast agent in the core of the prepared complex. The prepared multimodal theranostic system provides a safe and effective platform for fighting against cancer.

Effects of cellulose/salicylaldehyde thiosemicarbazone complexes on PVA based hydrogels: Portable, reusable, and high-precision luminescence sensing of Cu2

Novel portable, high-precision, and reusable fluorescent polyvinyl alcohol (PVA)-borax hydrogel sensors were prepared to detect Cu²⁺ in aqueous environment. A TEMPO-oxidized cellulose nanofibers/salicylaldehyde thiosemicarbazone (TOCN/ST) complex was further incorporated into the PVA-borax matrix. The in situ polymerization of TOCN/ST complex enhanced the mechanical properties of the hydrogels and improved the accuracy of detection. The resultant hydrogels were thermo reversible, and it converted to the liquid state during heating, which could greatly reduce the deviations caused in the detection of solid sensors. After cooling, the hydrogel could transform into the solid condition, which was easily portable. The sensor induced a significant luminescence quenching to the Cu²⁺ at 485 nm, with a detection limit of 0.086 μM. In the presence of ethylenediaminetetraacetic acid disodium, Cu²⁺ were tightly seized, causing the liberation of TOCN/ST complex and thus, a reversible "ON-OFF-ON" fluorescence behavior was displayed. The fluorescence intensity was maintained at 82 % after 10 uses, and the mechanical strength was maintained at 85 % after 3 uses. The anti-bacterial activity test also confirmed the TOCN/ST complex was extremely potent in suppressing the growth and reproduction of Escherichia coli. The proposed hydrogel provides a new insight into the detection of Cu²⁺ in aqueous environments.

Long-term glycemic control and prevention of diabetes complications in vivo using oleic acid-grafted-chitosan‑zinc-insulin complexes incorporated in thermosensitive copolymer

Daily injections for basal insulin therapy are far from ideal resulting in hypo/hyperglycemic episodes associated with fatal complications in type-1 diabetes patients. Here we report a delivery system that provides controlled release of insulin closely mimicking physiological basal insulin requirement for an extended period following a single subcutaneous injection. Stability of insulin was significantly improved by formation of zinc-insulin hexamers, further stabilized by electrostatic complex formation with chitosan polymer. Insulin complexes were homogenously incorporated into PLA-PEG-PLA, a biodegradable thermogel copolymer, that instantaneously forms a subcutaneous gel-depot following injection. Chitosan polymer was hydrophobically modified using oleic acid prior to complex formation with insulin to enable distribution of oleic acid-grafted-chitosan‑zinc-insulin complexes into the hydrophobic core of PLA-PEG-PLA thermogel-copolymer micelles. In vivo, daily administration of marketed long-acting insulin, glargine, resulted in fluctuating blood glucose levels between 91 and 443 mg/dL in type 1 diabetic rats. However, single administration of thermogel copolymeric formulation successfully demonstrated slow diffusion of insulin complexes maintaining peak-free basal insulin level of 21 mU/L for 91 days. Sustained release of basal insulin also correlated with efficient glycemic control (blood glucose <120 mg/dL), prevention of diabetic ketoacidosis and absence of cataract development, unlike other treatment groups. Moreover, there was no sign of inflammation, tissue damage, or collagen deposition around depot site, suggesting exceptional biocompatibility of the formulation for long-term use.

In Vitro Assessment of Core-Shell Micellar Nanostructures of Amphiphilic Cationic Polymer-Peptide Conjugates as Efficient Gene and Drug Carriers

Design and development of biocompatible, biodegradable and stable dual delivery systems for drug and gene is the need of the hour. Here, we have designed a strategy to develop carrier systems consisting of above mentioned properties by (a) incorporating an unnatural amino acid in the peptide backbone, and b) conjugating a low molecular weight cationic polymer (polyethylenimine, PEI) for incorporating cationic charge. Using this strategy, we have synthesized a small series of Boc-FΔF-AH-polyethylenimine conjugates by varying the concentration of Boc-FΔF-aminohexanoic acid, viz., PP-1, PP-2 and PP-3. These conjugates self-assembled in aqueous medium to form micelles in the size range of ~144-205 nm with zeta potential ~ +7.9-14.2 mV bearing core-shell type of conformation. Positive surface of the micelles facilitated the binding of plasmid DNA as well as transportation inside the cells. The hydrophobic core of the nanostructures helped in the encapsulation of the hydrophobic drug molecule, which was then got released in a controlled manner. DNA complexes of the conjugates were not only found non-toxic but also exhibited higher transfection efficacy than the native polymer and Lipofectamine. Altogether, these nanostructures are capable of delivering a drug and a gene simultaneously in vitro and could be used as next-generation delivery agents.

Polymer Microparticles with Defined Surface Chemistry and Topography Mediate the Formation of Stem Cell Aggregates and Cardiomyocyte Function

Surface-functionalized microparticles are relevant to fields spanning engineering and biomedicine, with uses ranging from cell culture to advanced cell delivery. Varying topographies of biomaterial surfaces are also being investigated as mediators of cell-material interactions and subsequent cell fate. To investigate competing or synergistic effects of chemistry and topography in three-dimensional cell cultures, methods are required to introduce these onto microparticles without modification of their underlying morphology or bulk properties. In this study, a new approach for surface functionalization of poly(lactic acid) (PLA) microparticles is reported that allows decoration of the outer shell of the polyesters with additional polymers via aqueous atom transfer radical polymerization routes. PLA microparticles with smooth or dimpled surfaces were functionalized with poly(poly(ethylene glycol) methacrylate) and poly[N-(3-aminopropyl)methacrylamide] brushes, chosen for their potential abilities to mediate cell adhesion. X-ray photoelectron spectroscopy and time-of-flight secondary ion mass spectrometry analysis indicated homogeneous coverage of the microparticles with polymer brushes while maintaining the original topographies. These materials were used to investigate the relative importance of surface chemistry and topography both on the formation of human immortalized mesenchymal stem cell (hiMSCs) particle-cell aggregates and on the enhanced contractility of cardiomyocytes derived from human-induced pluripotent stem cells (hiPSC-CMs). The influence of surface chemistry was found to be more important on the size of particle-cell aggregates than topographies. In addition, surface chemistries that best promoted hiMSC attachment also improved hiPSC-CM attachment and contractility. These studies demonstrated a new route to obtain topo-chemical combinations on polyester-based biomaterials and provided clear evidence for the predominant effect of surface functionality over micron-scale dimpled topography in cell-microparticle interactions. These findings, thus, provide new guiding principles for the design of biomaterial interfaces to direct cell function.

Bifunctionally engineered polyethylenimines as efficient DNA carriers and antibacterials against resistant pathogens

In this study, we have designed and developed two series of bifunctional conjugates by tethering polyethylenimine with streptomycin. By varying the amount of streptomycin, conjugates, polyethylenimine-streptomycin, have been synthesized and characterized spectroscopically. Gel electrophoresis assay revealed a slight decrease in the cationic charge density on the conjugates as these retarded the mobility of pDNA at higher w/w ratios. Further, transfection studies showed that both the series of conjugates transfected the mammalian cells efficiently with low-molecular weight polyethylenimine-streptomycin conjugates were more competent (∼9-fold enhancement with respect to native bPEI) exhibiting high cell viability too. Besides, both the series of conjugates displayed excellent antibacterial activity on pathogenic bacteria, even better than native streptomycin on resistant strains. Altogether, these results ensure the promising potential of the projected bifunctional conjugates as safe and efficient gene delivery vectors as well as antibacterials for future biomedical applications.

Antibacterial activity and cytotoxycity of gelatine-conjugated lysine-based peptides

The effect of the coupling approach (chemical by using carbodiimide chemistry, and enzymatic by using transglutaminase) of a hydrophilic ɛ-poly-L-lysine (ɛPL) and a structurally-hydrophobic oligo-acyl-lysyl (OAK) to a gelatine (GEL) macromolecule, and their antibacterial activity against Gram-negative E. coli and Gram-positive S. aureus bacteria, as well as cytotoxicity to human osteoblast cells was studied as potential macromolecules for biomedical applications. Different spectroscopic (ultraviolet-visible, infrared, fluorescence, and electron paramagnetic resonance) and separation (size-exclusion chromatography and capillary zone electrophoresis) techniques, as well as zeta-potential analysis were performed to confirm the ɛPL/OAK covalent coupling and to determine their amount and orientation of the immobilization. The highest and kinetically the fastest reduction of bacteria (≥77% against E. coli vs. ≥82% against S. aureus) was achieved with GEL functionalized with ɛPL/OAK by the chemical grafting-to approach being correlated with conformationally the highly-flexible ˝brush-like˝ orientation linkage of peptides, enable its targeted and rapid interactions with bacteria membrane. The up to 400-fold lower yield of OAKs being immobilized may be related also to its cationic charge and hydrophobic alkyl chain moieties, compared to more hydrophilic ɛPL easily causing random polymerization and self-conjugation. The ɛPL/OAK-functionalized GEL did not induce citotoxicity to osteoblasts, even at ∼25-fold higher concentration than bacterial minimum inhibitory (MIC) concentration of ɛPL/OAK. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 3110-3126, 2017.

Supermacroporous chemically cross-linked poly(aspartic acid) hydrogels

Chemically cross-linked poly(aspartic acid) (PASP) gels were prepared by a solid-liquid phase separation technique, cryogelation, to achieve a supermacroporous interconnected pore structure. The precursor polymer of PASP, polysuccinimide (PSI) was cross-linked below the freezing point of the solvent and the forming crystals acted as templates for the pores. Dimethyl sulfoxide was chosen as solvent instead of the more commonly used water. Thus larger temperatures could be utilized for the preparation and the drawback of increase in specific volume of water upon freezing could be eliminated. The morphology of the hydrogels was characterized by scanning electron microscopy and interconnectivity of the pores was proven by the small flow resistance of the gels. Compression tests also confirmed the interconnected porous structure and the complete re-swelling and shape recovery of the supermacroporous PASP hydrogels. The prepared hydrogels are of interest for several biomedical applications as scaffolding materials because of their cytocompatibility, controllable morphology and pH-responsive character.