Lignin-Based Nonviral Gene Carriers Functionalized by Poly[2-(Dimethylamino)ethyl Methacrylate]: Effect of Grafting Degree and Cationic Chain Length on Transfection Efficiency

Lignin is a natural renewable biomass resource with great potential for applications, while its development into high value-added molecules or materials is rare. The development of biomass lignin as potential nonviral gene delivery carriers was initiated by our group through the “grafting-from” approach. Firstly, the lignin was modified into macroinitiator using 2-bromoisobutyryl bromide. Then cationic polymer chains of poly[2-(dimethylamino)ethyl methacrylate] (PDMAEMA) were grown from the lignin backbone using atom transfer radical polymerization (ATRP) to yield lignin-PDMAEMA graft copolymers (LPs) with branched structure. To gain a deep understanding of the relationship between the nonviral gene transfection efficiency of such copolymers and their structural and compositional factors, herein eight lignin-based macroinitiators with different modification degrees (MDs, from 3.0 to 100%) were synthesized. Initiated by them, a series of 20 LPs were synthesized with varied structural factors such as grafting degree (GD, which is equal to MD, determining the cationic chain number per lignin macromolecule), cationic chain length (represented by number of repeating DMAEMA units per grafted arm or degree of polymerization, DP) as well as the content of N element (N%) which is due to the grafted PDMAEMA chains and proportional to molecular weight of the LPs. The in vitro gene transfection capability of these graft copolymers was evaluated by luciferase assay in HeLa, COS7 and MDA-MB-231cell lines. Generally, the copolymers LP-12 (N% = 7.28, MD = 36.7%, DP = 13.6) and LP-14 (N% = 6.05, MD = 44.4%, DP = 5.5) showed good gene transfection capabilities in the cell lines tested. Overall, the performance of LP-12 was the best among all the LPs in the three cell lines at the N/P ratios from 10 to 30, which was usually several times higher than PEI standard. However, in MDA-MB-231 at N/P ratio of 30, LP-14 showed the best gene transfection performance among all the LPs. Its gene transfection efficiency was ca. 11 times higher than PEI standard at this N/P ratio. This work demonstrated that, although the content of N element (N%) which is due to the grafted PDMAEMA chains primarily determines the gene transfection efficiency of the LPs, it is not the only factor in explaining the performance of such copolymers with the branched structure. Structural factors of these copolymers such as grafting degree and cationic chain length could have a profound effect on the copolymer performance on gene transfection efficiency. Through carefully adjusting these factors, the gene transfection efficiency of the LPs could be modulated and optimized for different cell lines, which could make this new type of biomass-based biomaterial an attractive choice for various gene delivery applications.

Influence of spin finish on degradation, functionalization and long-term storage of polyethylene terephthalate fabrics dedicated to ligament prostheses

Polyethylene terephthalate (PET) fibers and fabrics are widely used for medical device applications such as vascular and anterior cruciate ligament prostheses. Several years ago, we began functionalizing PET fabrics using anionic polymers to enhance their biocompatibility, cell adhesion, proliferation and functional performance as PET ligament prostheses. Polymer functionalization followed a grafting-from process from virgin PET surfaces subject to spin-finish oil additive removal under Soxhlet extraction to remove residual fiber manufacturing oil. Nevertheless, with increasing time from manufacture, PET fabrics stored without a spin finish removal step exhibited degradation of spin finish oil, leading to (1) incomplete surface cleaning, and (2) PET surface degradation. Moreover, oxidizing agents present in the residual degraded oil prevented reliable functionalization of the prosthesis fibers in these PET fabrics. This study compares effects of PET fabric/spin finish oil storage on PET fabric anionic polymer functionalization across two PET fabric ligament storage groups: (1) 2- and 10- year old ligaments, and (2) 26-year old ligaments. Strong interactions between degraded spin finish oil and PET fiber surfaces after long storage times were demonstrated via extraction yield; oil chemistry changed assessed by spectral analysis. Polymer grafting/functionalization efficiency on stored PET fabrics was correlated using atomic force microscopy, including fiber surface roughness and relationships between grafting degree and surface Young’s modulus. New PET fabric Young’s modulus significantly decreased by anionic polymer functionalization (to 96%, grafting degree 1.6 µmol/g) and to reduced modulus and efficiency (29%) for 10 years storage fabric (grafting degree ~ 1 µmol/g). As fiber spin finish is mandatory in biomedically applicable fiber fabrication, assessing effects of spin finish oil on commercial polymer fabrics after longer storage under various conditions (UV light, temperature) is necessary to understand possible impacts on fiber degradation and surface functionalization.

Theoretical and Experimental Optimization of the Graft Density of Functionalized Anti-Biofouling Surfaces by Cationic Brushes

Diseases and complications related to catheter materials are severe problems in biomedical material applications, increasing the infection risk and medical expenses. Therefore, there is an enormous demand for catheter materials with antibacterial and antifouling properties. Considering this, in this work, we developed an approach of constructing antibacterial surfaces on polyurethane (PU) via surface-initiated atom transfer radical polymerization (SI-ATRP). A variety of cationic polymers were grafted on PU. The biocompatibility and antifouling properties of all resulting materials were evaluated and compared. We also used a theoretical algorithm to investigate the anticoagulant mechanism of our PU-based grafts. The hemocompatibility and anti-biofouling performance improved at a 86–112 μg/cm2 grafting density. The theoretical simulation demonstrated that the in vivo anti-fouling performance and optimal biocompatibility of our PU-based materials could be achieved at a 20% grafting degree. We also discuss the mechanism responsible for the hemocompatibility of the cationic brushes fabricated in this work. The results reported in this paper provide insights and novel ideas on material design for applications related to medical catheters.

Organically Modified Montmorillonite as Nanoreactor to Improve the Grafting Degree of Maleic Anhydride onto Polypropylene

The application of an organically modified montmorillonite nanoreactor in the reactive extrusion process of the free radical grafting of maleic anhydride onto polypropylene (PP) can increase the MAH grafting degree on the PP. The mechanism of grafting was studied by using transmission electron microscopy and high temperature gel permeation chromatography. It was found that both the strong interactions between MAH and MMT surface and the encapsulation effect of active species confined in o-MMT improved the grafting degree.

Crystallization, Structures, and Properties of Different Polyolefins with Similar Grafting Degree of Maleic Anhydride

Maleic anhydride (MAH) grafting to different polyolefins with similar grafting degree can have different effects on crystallization, crystal structure, and mechanical and thermal properties. The grafting leads to a smaller crystal size, less ordered lamellar structure, and a shorter long period for HDPE, LLDPE, and PP. The grafting makes PP lamellar packing less ordered the most and almost no effect to LLDPE. The grafting does not have that much impact on the crystallization ability of the HDPE, LLDPE, and HDPE/PP blend, but appreciably reduces the crystalline ability of PP-g-MAH, due to a dramatical drop in its molecular weight during the grafting process. As a result, the grafting makes PP a very brittle material with a lowered average melting point than the corresponding neat PP, but the grafting has almost no effect on elongation at break for LLDPE and some effect on HDPE (decreased by one-third). However, the PP degradation due to MAH grafting can be avoided in the presence of PE component, i.e., making the grafting of PP and PE at the same time with HDPE/PP blend. The grafted HDPE/PP blend shows a significantly improved compatibility, which leads to overall appreciably better mechanical properties than the neat HDPE/PP blend.

ACRYLIC-CASEIN LATEXES WITH POTENTIAL APPLICATION AS ADHESIVES

The replacement of monomers derived from petrochemical sources by biopolymers like proteins, together with the development of new materials with improved properties, have an increasing importance in industrial applications. In this context, the synthesis of acrylic-casein hybrid latexes was investigated through a low environmental impact strategy, such as the surfactant-free emulsion polymerization, with the aim of producing new industrial adhesives. Different aspects of the synthesis of hybrid latexes were addressed, such us i) the use of variable content of protein; ii) the control of grafting degree between polymers, using native casein (without chemical modification) or functionalized casein, and iii) the employment of a chain transfer agent to reduce molecular weights of the acrylic polymer. The effect of the analyzed variables on the polymerization kinetics, the degree of compatibility between polymers, and the application properties of the produced latexes as adhesives were investigated.

Choline supported poly(ionic liquid) graft copolymers as novel delivery systems of anionic pharmaceuticals for anti-inflammatory and anti-coagulant therapy

New type of carriers based on grafted poly(ionic liquid)s was designed for delivery of ionically attached salicylates (Sal). Choline derived ionic liquid monomeric units were successfully introduced with various content in the side chains by the controlled radical polymerization. Properly high amounts of ionic pharmaceutics in the polymer systems were achieved by the well-fitted length and grafting degree of the side chains. In aqueous solution the graft copolymers were self-assembled into the spherical superstructures with sizes up to 73 nm. Delivery studies showed “burst” release within 4 h, after that it was slower yielding ~70% of released drug within 80 h. Proposed nanocarriers supported low toxicity against human cells (NHDF and BEAS-2B), anti-inflammation activity evaluated with the use of pro-inflammatory interleukins (IL-6 and IL-8) and antibacterial activities towards E. coli. Adjustment of ionic drug content by structural parameters of graft copolymers, including grafting degree and graft length, are advantageous to tailor nanocarriers with self-assembly properties in aqueous media. Effective release process by ionic exchange and biological activity with low toxicity are promising for further development of this type of drug delivery (DDS).

The research determines appropriate parameters in the synthesis process of syringic acid grafted chitooligosaccharides

Introduction: The aim of this study is to determine appropriate parameters in the synthesis of syringic acid onto chitooligosaccharides (COSs) with an ascorbic acid/hydrogen peroxide redox pair in order to obtain the derivative with the highest grafting degree. Methods: In this study, syringic acid grafted COSs, catalysed by an ascorbic acid/hydrogen peroxide redox pair were investigated. The synthesis conditions were investigated, including the mass ratio between syringic acid and COSs, pH, temperature and synthesis time. Characteristics of the derivative were evaluated by Thin Layer Chromatography (TLC), Ultraviolet-Visible (UV-vis) and Fourier Transform Infrared (FT-IR) spectroscopy. The activities of COSs and derivative were evaluated by antimicrobial ability. Results: The results showed, that the best conditions for the synthesis were the mass ratio between syringic acid and COSs at 0.5:1, pH 5, temperature 27oC, for 6 hours with grafting degree at 32%. The TLC assay showed, that free ascorbic acid and syringic acid are not present in the product. The UV-vis and FT-IR data confirmed, that syringic acid was successfully conjugated onto COSs. Furthermore, the antibacterial assay showed that syringic acid grafted onto COSs had minimum inhibitory concentration against foodborne pathogenic bacteria at 1%. Conclusion: The syringic acid onto chitooligosaccharides were successfully synthesized by free radical mediated grafting method with an ascorbic acid/hydrogen peroxide redox pair. The grafting degree of syringic acid onto COSs was greatly affected by many factors, including COSs, syringic acid, pH, as well as temperature and time of reaction. Moreover, the new derivative showed enhanced antibacterial capabilities, as compare to free COSs.