Amphiphilic triblock copolymers of methoxy-poly(ethylene glycol)-b-poly(L-lactide)-b-poly(L-lysine) for enhancement of osteoblast attachment and growth

Layer-by-Layer Assembly of Ag@Ti3C2TX and Chitosan on PLLA Substrate to Enhance Antibacterial and Biocompatibility

Poly L-lactic acid (PLLA) is a non-toxic, biocompatible degradable polymer material with excellent mechanical properties after molding. However, it faces challenges in the use of biomedical materials because of its intolerance to bacteria. Here, we use an easy-to-operate method to prepare a composite multilayer membrane: PLLA membrane was used as substrates to assemble positively charged chitosan and negatively charged Ag@MXene on the surface using the Layer-by-layer (LBL) method. The assembly process was detected by Fluorescein Isothiocyanate (FITC)-labelled chitosan and the thickness of the coating multilayer was also detected as 210.0 ± 12.1 nm for P-M membrane and 460.5 ± 26.5 nm for P-Ag@M membrane. The surface self-assembled multilayers exhibited 91.27% and 96.11% growth inhibition ratio against E. coli and S. aureus strains under 808 nm near-infrared (NIR) laser radiation with a synergistic photothermal antibacterial effect. Furthermore, best biocompatibility of P-M and P-Ag@M membranes compare to PLLA membrane motivated us to further explore its application in biomedical materials.

Biocompatible polypeptide-based interpenetrating network (IPN) hydrogels with enhanced mechanical properties

Hydrogels are widely used for biomedical applications such as drug delivery, tissue engineering, or wound healing owing to their mimetic properties in relation to biological tissues. The generation of peptide-based hydrogels is a topic of interest due to their potential to increase biocompatibility. However, their usages can be limited when compared to other synthetic hydrogels because of their inferior mechanical properties. Herein, we present the synthesis of novel synthetic polypeptide-based interpenetrating network (IPN) hydrogels with enhanced mechanical properties. The polypeptide single network is obtained from alkyne functional polypeptides crosslinked with di, tri and tetra azide functional PEG by copper-catalysed alkyne-azide cycloaddition (CuAAC). Interpenetrating networks were subsequently obtained by loading of the polypeptide single network with PEG-dithiol and orthogonally UV-crosslinking with varying molar ratios of pentaerythritol tetraacrylate. The characteristics, including the mechanical strength (i.e. compressive strength (UCS), fracture strain (ε_break), and Young's modulus (E)) and cell compatibility (i.e. metabolic activity and Live/Dead of human Mesenchymal Stem Cells), of each synthetic polypeptide-based IPN hydrogel were studied and evaluated in order to demonstrate their potential as mechanically robust hydrogels for use as artificial tissues. Moreover, ¹H NMR diffusometry was carried out to examine the water mobility (D_H2O) within the polypeptide-based hydrogels and IPNs. It was found that both the mechanical and morphological properties could be tailored concurrently with the hydrophilicity, rate of water diffusion and 'swellability'. Finally it was shown that the polypeptide-based IPN hydrogels exhibited good biocompatibility, highlighting their potential as soft tissue scaffolds.

Development of an Anti-Inflammatory Drug-Incorporated Biomimetic Scaffold for Corneal Tissue Engineering

Purpose: The aim of this study was to design naproxen sodium (NS)-containing, biomimetic, porous poly(lactide-co-glycolide) (PLGA) scaffolds for regeneration of damaged corneal epithelium. Methods: NS-incorporated PLGA scaffolds were prepared using the emulsion freeze-drying method and then coated with collagen or poly-l-lysine. Porosity measurements of the scaffolds were performed by the gas adsorption/desorption method and the scaffolds demonstrated highly porous, open-cellular pore structures with pore sizes from 150 to 200 μm. Results: The drug loading efficiency of scaffolds was found to be higher than 84%, and about 90%-98% of NS was released at the end of 7 days with a fast drug release rate at the initial period of time and then in a slow and sustained manner. The corneal epithelial cells were isolated from New Zealand white rabbits. The obtained cells were seeded onto scaffolds and continued to increase during the time period of the study, indicating that the scaffolds might promote corneal epithelial cell proliferation without causing toxic effects for at least 10 days. Conclusions: The NS-loaded PLGA scaffolds exhibited a combination of controlled drug release and biomimetic properties that might be attractive for use in treatment of corneal damage both for controlled release and biomedical applications.

Modification of porous PLGA microspheres by poly-l-lysine for use as tissue engineering scaffolds

Due to their good biocompatibility, biodegradability and special shapes, porous poly(lactic-co-glycolic acid) (PLGA) microspheres show a wide application in the field of tissue engineering. Herein we demonstrate a simple and low-cost method for modifying porous PLGA microspheres with poly-l-lysine (PLL) to promote cell growth on the microspheres. Porous PLGA microspheres were first treated by sodium hydroxide (NaOH) solution to introduce carboxyl groups on their surface. Then, the hydrolyzed microspheres (PLGA-H) were immerged in PLL solution to yield PLL-impregnated microspheres (PLGA-PLL). Cell experiments showed that although the cytotoxicity of microspheres was slightly increased after PLL modification, their cell viability was still higher than 85%. Compared with PLGA and PLGA-H microspheres, PLGA-PLL microspheres were more favorable for MG63 cell to attach and proliferate due to their increased initial cell attachment numbers and enhanced cell-matrix interactions. This new modification method of porous PLGA microspheres proposes a route toward efficient repair of tissue defects at reduced risk and cost level.

Thermo-Responsive Polyurethane Hydrogels Based on Poly(ε-caprolactone) Diol and Amphiphilic Polylactide-Poly(Ethylene Glycol) Block Copolymers

Waterborne polyurethane (PU) based on poly(ε-caprolactone) (PCL) diol and an amphiphilic polylactide-poly(ethylene glycol) (PLA-PEG) diblock copolymer was synthesized. The molar ratio of PCL/PLA-PEG was 9:1 with different PLA chain lengths. The PU nanoparticles were characterized by dynamic light scattering (DLS), small angle X-ray scattering (SAXS) and rheological analysis. The water contact angle measurement, infrared spectroscopy, wide angle X-ray scattering (WAXS), thermal and mechanical analyses were conducted on PU films. Significant changes in physio-chemical properties were observed for PUs containing 10 mol % of amphiphilic blocks. The water contact angle was reduced to 12°⁻13°, and the degree of crystallinity was 5%⁻10%. The PU dispersions underwent sol-gel transition upon the temperature rise to 37 °C. The gelation time increased as the PLA chain length increased. In addition, the fractal dimension of each gel was close to that of a percolation cluster. Moreover, PU4 with a solid content of 26% could support the proliferation of human mesenchymal stem cells (hMSCs). Therefore, thermo-responsive hydrogels with tunable properties are promising injectable materials for cell or drug delivery.

Biodegradable PEG-Based Amphiphilic Block Copolymers for Tissue Engineering Applications

Biodegradable tissue engineering scaffolds have great potential for delivering cells/therapeutics and supporting tissue formation. Polyesters, the most extensively investigated biodegradable synthetic polymers, are not ideally suited for diverse tissue engineering applications due to limitations associated with their hydrophobicity. This review discusses the design and applications of amphiphilic block copolymer scaffolds integrating hydrophilic poly(ethylene glycol) (PEG) blocks with hydrophobic polyesters. Specifically, we highlight how the addition of PEG results in striking changes to the physical properties (swelling, degradation, mechanical, handling) and biological performance (protein & cell adhesion) of the degradable synthetic scaffolds in vitro. We then perform a critical review of how these in vitro characteristics translate to the performance of biodegradable amphiphilic block copolymer-based scaffolds in the repair of a variety of tissues in vivo including bone, cartilage, skin, and spinal cord/nerve. We conclude the review with recommendations for future optimizations in amphiphilic block copolymer design and the need for better-controlled in vivo studies to reveal the true benefits of the amphiphilic synthetic tissue scaffolds.

Hydrogels assembled from star-shaped polypeptides with a dendrimer as the core

A second or fourth generation dendrimer with primary amine as the peripheral terminal group was first synthesized via Michael addition and thiol-yne addition. A series of star-shaped polypeptides was synthesized by ring opening polymerization (ROP) of γ-(2-(2-methoxyethoxy)ethyl) l-glutamate (l-EG2Glu) N-carboxyanhydride (NCA) using the amine group terminated dendrimer as the initiator. Taking advantage of the well-defined dendrimer and ROP, the arm number and arm length can be easily controlled. These star-shaped poly(l-EG2Glu) can spontaneously form hydrogels instead of micelles in water at low concentration. The critical gelation concentration (CGC) and hydrogel strength displayed a stronger dependence on arm numbers than the arm length under similar conditions. These properties can be easily modulated by varying the poly(l-EG2Glu) arm length and arm number. The hydrogels showed shear thinning and rapid recovery properties. TEM and AFM characterization revealed that the hydrogel networks were constituted by entangled and branched fibrils.

Preparation and characterization of bimodal porous poly(γ-benzyl-L-glutamate) scaffolds for bone tissue engineering

An ideal scaffold in bone tissue-engineering strategy should provide biomimetic extracellular matrix-like architecture and biological properties. Poly(γ-benzyl-L-glutamate) (PBLG) has been a popular model polypeptide for various potential biomedical applications due to its good biocompatibility and biodegradability. This study developed novel bimodal porous PBLG polypeptide scaffolds via a combination of biotemplating method and in situ ring-opening polymerization of γ-benzyl-L-gIutamate N-carboxyanhydride (BLG-NCA). The PBLG scaffolds were characterized by proton nuclear magnetic resonance spectroscopy, X-ray diffraction, differential scanning calorimetry, scanning electron microscope (SEM) and mechanical test. The results showed that the semi-crystalline PBLG scaffolds exhibited an anisotropic porous structure composed of honeycomb-like channels (100-200 μm in diameter) and micropores (5-20 μm), with a very high porosity of 97.4±1.6%. The compressive modulus and glass transition temperature were 402.8±20.6 kPa and 20.2°C, respectively. The in vitro biocompatibility evaluation with MC3T3-E1 cells using SEM, fluorescent staining and MTT assay revealed that the PBLG scaffolds had good biocompatibility and favored cell attachment, spread and proliferation. Therefore, the bimodal porous polypeptide scaffolds are promising for bone tissue engineering.

Silk ionomers for encapsulation and differentiation of human MSCs

The response of human bone marrow derived human mesenchymal stem cells (hMSCs) encapsulated in silk ionomer hydrogels was studied. Silk aqueous solutions with silk-poly-L-lysine or silk-poly-L-glutamate were formed into hydrogels via ultrasonication in situ with different net charges. hMSCs were encapsulated within the hydrogels and the impact of matrix charge was assessed over weeks in osteogenic, adipogenic and maintenance growth media. These modified silk charged polymers supported cell viability and proliferative potential, and the hMSCs were able to differentiate toward osteogenic or adipogenic lineages in the corresponding differentiation media. The silk/silk-poly-L-lysine hydrogels exhibited a positive effect on selective osteogenesis of hMSCs, inducing differentiation toward an osteogenic lineage even in the absence of osteogenic supplements, while also inhibiting adipogenesis. In contrast, silk/silk fibroin-poly-L-glutamate hydrogels supported both osteogenic and adipogenic differentiation of hMSCs when cultured under induction conditions. The results demonstrate the potential utility of silk-based ionomers in gel formats for hMSCs encapsulation and for directing hMSCs long term functional differentiation toward specific lineages.

Preparation of the Amphiphilic Copolymer of Poly(ethyleneoxid-co-glycidol)-Graft-Poly(lactide) and their Extraction for Dyes

A well-defined graft copolymer poly(ethylene oxide-co-glycidol)-graft-Poly(lactide) [poly(EO-co-Gly)-g-PLA] of poly(ethylene oxide-co-glycidol) [(poly(EO-co-Gly)] as main chain and poly(lactide) (PLA) as the side chain was successfully prepared via combination of anionic polymerization and ring-opening polymerization. The glycidol was protected by ethyl vinyl ether first to form 2, 3-epoxypropyl-1-ethoxyethyl ether (EPEE), and then copolymerized with EO by initiation with the mixture of diphenylmethylpotassium and triethylene glycol to obtain the well-defined poly(EO-co-EPEE). The latter was hydrolyzed in the acidic conditions and then coordination-insertion ring-opening polymerization of lactide(LA) with poly(EO-co-Gly) was completed. The object products and intermediates were characterized by 1HNMR, MALDI-TOF-MS and GPC in detail. The experimental results confirmed that poly(EO-co-Gly)-g-PLA showed strong conjugation ability with the dyes.

Amphiphilic polylactic acid-hyperbranched polyglycerol nanoparticles as a controlled release system for poorly water-soluble drugs: physicochemical characterization

Objectives

Quercetin was applied as a model drug to evaluate the potential application of amphiphilic polylactic acid-hyperbranched polyglycerol (HPG-PLA) nanoparticles as carriers for poorly water-soluble drugs.

Methods

The drug delivery systems were characterized by dynamic light scattering, powder X-ray diffraction (XRD) and Fourier-transform infrared spectroscopy (FTIR) and so forth.

Key findings

The results showed the particle sizes ranged from 205.3 to 433.3 nm with low polydispersity index. XRD and FTIR demonstrated that the crystal of the drug was converted to an amorphous state in the matrices and formed intermolecular interaction with carriers. The drug encapsulation efficiency and drug loading could reach 91.8% and 21.0%, respectively. Cell viability assay suggested the nanoparticles had good cytocompatibility. The in-vitro drug release profiles showed a sustained quercetin release up to 192 h, indicating the suitability of nanoparticles in sustained drug release. Furthermore, the influence of many factors on release profiles could also be evaluated for the potential of using nanoparticles as controlled release systems.

Conclusions

This system may be of clinical importance in both stabilizing and delivering hydrophobic drugs for the treatment of many diseases.

α-Amino acid containing degradable polymers as functional biomaterials: rational design, synthetic pathway, and biomedical applications

Currently, biomedical engineering is rapidly expanding, especially in the areas of drug delivery, gene transfer, tissue engineering, and regenerative medicine. A prerequisite for further development is the design and synthesis of novel multifunctional biomaterials that are biocompatible and biologically active, are biodegradable with a controlled degradation rate, and have tunable mechanical properties. In the past decades, different types of α-amino acid-containing degradable polymers have been actively developed with the aim to obtain biomimicking functional biomaterials. The use of α-amino acids as building units for degradable polymers may offer several advantages: (i) imparting chemical functionality, such as hydroxyl, amine, carboxyl, and thiol groups, which not only results in improved hydrophilicity and possible interactions with proteins and genes, but also facilitates further modification with bioactive molecules (e.g., drugs or biological cues); (ii) possibly improving materials biological properties, including cell-materials interactions (e.g., cell adhesion, migration) and degradability; (iii) enhancing thermal and mechanical properties; and (iv) providing metabolizable building units/blocks. In this paper, recent developments in the field of α-amino acid-containing degradable polymers are reviewed. First, synthetic approaches to prepare α-amino acid-containing degradable polymers will be discussed. Subsequently, the biomedical applications of these polymers in areas such as drug delivery, gene delivery and tissue engineering will be reviewed. Finally, the future perspectives of α-amino acid-containing degradable polymers will be evaluated.

Materials for pharmaceutical dosage forms: molecular pharmaceutics and controlled release drug delivery aspects

Controlled release delivery is available for many routes of administration and offers many advantages (as microparticles and nanoparticles) over immediate release delivery. These advantages include reduced dosing frequency, better therapeutic control, fewer side effects, and, consequently, these dosage forms are well accepted by patients. Advances in polymer material science, particle engineering design, manufacture, and nanotechnology have led the way to the introduction of several marketed controlled release products and several more are in pre-clinical and clinical development.