Hydrolytic Degradation Properties Research Articles

Accelerated hydrolytic degradation of poly(l-lactide) by blending with poly(ether-block-amide)

A continuing challenge in the most common biodegradable polyester of poly(l-lactide) (PLLA) is to improve the degradation rate in the environment, though it has been widely used in packaging and medical applications. In this study, PLLA/poly(ether-block-amide) (PEBA) blends are prepared by melt blending to investigate the effect of PEBA component on the phase morphology, thermal behavior, mechanical properties, and hydrolytic degradation of the blends. The incorporation of PEBA component is beneficial to the improved toughness and increased water absorption of the blends, and accelerated hydrolytic degradation of PLLA. The blend exhibits the optimal mechanical and hydrolytic degradation properties when the blend mass ratio of PLLA/PEBA is 80/20. The toughness of the blend is increased by 390 % compared to that of pure PLLA. After being hydrolyzed at 58 °C for 240 h, the water absorption, the mass loss and the decrease of molecular weight of the blend is increased by 138 %, 160 % and 40 %, respectively, indicating faster hydrolytic degradation rate of the blend than that of pure PLLA. Furthermore, the accelerated hydrolytic degradation mechanism of PLLA in the blend is revealed. The amorphous region of PLLA is hydrolyzed initially at the phase interface of the blend, and subsequently the crystalline structure of PLLA is degraded. The hydrolysis process causes a change in the relative content of crystalline regions in the system, resulting in an increase in crystallinity of PLLA first and then decrease. These findings provide a new strategy for the design of novel degradable PLLA materials for practical applications.

Sequentially crosslinked collagen‐based hydrogel to form a semi‐interpenetrating network for enhanced stability to hydrolytic degradation and electrochemical properties

Sequentially crosslinked collagen‐based hydrogel to form a semi‐interpenetrating network for enhanced stability to hydrolytic degradation and electrochemical properties

Mechanical and thermal properties of bio-based polycarbonate/acrylonitrile-styrene-acrylate blends

The combination of the best properties of Polycarbonate (PC) and Acrylonitrile-butadiene-styrene (ABS) has resulted in the development of commercially available PC/ABS blends that have been found to be useful in many molding applications. PC has excellent mechanical and optical properties, but predominant use of bisphenol A in PC synthesis raises concerns regarding its potential environmental harm. In this study, we have studied the alternative for the PC/ABS blend by replacing PC with the bio-based PC and ABS with the Acrylonitrile-styrene-acrylate (ASA). A blend of bio-based PC and ASA was prepared by the melt blending techniques and investigated mechanical, thermal, and degradation (hydrolytic and soil burial degradation) properties.

The Influence of the Molecular Weight of Poly(Ethylene Oxide) on the Hydrolytic Degradation and Physical Properties of Polycaprolactone Binary Blends

The use of biodegradable polymers in tissue engineering has been widely researched due to their ability to degrade and release their components in a controlled manner, allowing for the potential regeneration of tissues. Melt blending is a common method for controlling the degradation rate of these polymers, which involves combining these materials in a molten state to create a homogenous mixture with tailored properties. In this study, polycaprolactone (PCL) was melt blended with hydrophilic poly (ethylene oxide) (PEO) of different molecular weights to assess its effect on PCL material performance. Hydrolytic degradation, thermal and viscoelastic properties, and surface hydrophilicity were performed to contrast the properties of the blends. DSC, DMA, and FTIR were performed on selected degraded PCL/PEO specimens following mass loss studies. The results showed that adding PEO to PCL reduced its melt viscosity-torque and melt temperature while increasing its hydrophilicity, optimizing PCL/PEO blend for soft tissue engineering applications and could contribute to the development of more effective and biocompatible materials for soft tissue regeneration.

Highly porous biobased membranes via electrospinning of PBS and CTAB

The field of nanofiber research has been gradually shifting towards sustainable materials, but the main challenges include modifying their properties to fit specific needs and applications. In this study, ultrathin and porous biobased poly(butylene succinate) (PBS) membranes were fabricated using electrospinning. The neat PBS polymer was found to be very difficult to process, but defect-free nanofibers were generated by adding cetyltrimethylammonium bromide (CTAB) as a surfactant. To determine the effect of CTAB on PBS membranes, extensive characterization of the newly developed material was performed, including morphology, wettability, water absorption, thermal, mechanical, and hydrolytic degradation properties. Scanning electron microscopy (SEM) showed that adding 0.04% w/v of CTAB produced smooth and beadless nanofibers with an average diameter of 380 nm. The presence of CTAB, as a surfactant, significantly improved the membrane porosity and generated higher hydrophilicity even when starting with an intrinsically hydrophobic material (original PBS). The result was a higher water absorption and hydrolytic degradation of the membrane. On the mechanical side, the surfactant highly improved the elongation at break from 51% for the neat PBS membrane to 192% for the PBS/CTAB membrane with 0.04% w/v CTAB. However, CTAB addition had a negligible effect on thermal stability and crystallinity. The results of this study showed that the high porosity and hydrophilicity of PBS/CTAB electrospun membranes, combined with their outstanding water absorption capacity, elasticity, and biodegradability, present a novel solution for enhancing the performance and functionality of biomaterials in various biomedical fields, especially in tissue engineering and wound dressing applications.

The role of three-dimensional scaffolds based on polyglycerol sebacate/ polycaprolactone/ gelatin in the presence of Nanohydroxyapatite in promoting chondrogenic differentiation of human adipose-derived mesenchymal stem cells

BackgroundTissue engineering for cartilage regeneration has made great advances in recent years, although there are still challenges to overcome. This study aimed to evaluate the chondrogenic differentiation of human adipose-derived mesenchymal stem cells (hADSCs) on three-dimensional scaffolds based on polyglycerol sebacate (PGS) / polycaprolactone (PCL) / gelatin(Gel) in the presence of Nanohydroxyapatite (nHA).Materials and methodsIn this study, a series of nHA-nanocomposite scaffolds were fabricated using 100:0:0, 60:40:0, and 60:20:20 weight ratios of PGS to PCL: Gel copolymers through salt leaching method. The morphology and porosity of prepared samples was characterized by SEM and EDX mapping analysis. Also, the dynamic contact angle and PBS adsorption tests are used to identify the effect of copolymerization and nanoparticles on scaffolds' hydrophilicity. The hydrolytic degradation properties were also analyzed. Furthermore, cell viability and proliferation as well as cell adhesion are evaluated to find out the biocompatibility. To determine the potential ability of nHA-nanocomposite scaffolds in chondrogenic differentiation, RT-PCR assay was performed to monitor the expression of collagen II, aggrecan, and Sox9 genes as markers of cartilage differentiation.ResultsThe nanocomposites had an elastic modulus within a range of 0.71–1.30 MPa and 0.65–0.43 MPa, in dry and wet states, respectively. The PGS/PCL sample showed a water contact angle of 72.44 ± 2.2°, while the hydrophilicity significantly improved by adding HA nanoparticles. It was found from the hydrolytic degradation study that HA incorporation can accelerate the degradation rate compared with PGS and PGS/PCL samples. Furthermore, the in vitro biocompatibility tests showed significant cell attachment, proliferation, and viability of adipose-derived mesenchymal stem cells (ADMSCs). RT-PCR also indicated a significant increase in collagen II, aggrecan and Sox9 mRNA levels.ConclusionsOur findings demonstrated that these nanocomposite scaffolds promote the differentiation of hADSCs into chondrocytes possibly by the increase in mRNA levels of collagen II, aggrecan, and Sox9 as markers of chondrogenic differentiation. In conclusion, the addition of PCL, Gelatin, and HA into PGS is a practical approach to adjust the general features of PGS to prepare a promising scaffold for cartilage tissue engineering.Graphical

In vitro hydrolytic degradation properties of poly(D, L-lactic acid) / poly(L-lactide-co-ε-caprolactone) blend films

Abstract Biodegradable materials are widely used in biomedical application. Blending polymers have become a promising strategy to regulate degradation rate and expand material properties. In this study, the poly(D, L-lactic acid) (PDLLA) and polyCL-lactide-co-ɛ-caprolactone) (PLcCL) blend films with different ratios were prepared by the ultrasonic spray technology and the in vitro hydrolytic degradation tests of these films were then carried out in phosphate buffered saline with 37°C and 50°C. The in vitro degradation of the blend films were investigated via mass loss, gel permeation chromatography (GPC), scanning electron microscopy (SEM). It was found that the blended film had good miscibility and uniformity through SEM tests. Besides, the 50/50 PLcCL/PDLLA film showed the slowest degradation rate at 37°C, while at 50°C, the 100 PLcCL film had the slowest degradation. This work can provide helpful suggestions for the evaluation of biodegradable polymer coating materials in degradable polymer coated stent.

Dual-jet electrospun PDLGA/PCU nonwovens and their mechanical and hydrolytic degradation properties

A dual-jet electrospinning was used to mix a different hydrophilicity poly(carbonate urethanes) (PCUs) nanofibers with a biodegradable poly(D,L-lactide-co-glycolide) (PDLGA) copolyester microfibers. As a result, PDLGA/PCU partially degradable nonwovens consisting of an interlaced of both components fibers were obtained. In order to examine the hydrolytic degradation process of polyester fraction, as well as changes that occurred in the mechanical properties of the whole nonwovens, gel permeation chromatography, proton nuclear magnetic resonance spectroscopy, differential scanning calorimetry and scanning electron microscopy as well as static tensile test were performed. Obtained results showed that for the introduction of more hydrophobic PCU nanofibers (ChronoSil), the process of copolyester chain scission slowed down and the erosion mechanism proceeded in bulk. Unexpectedly, even greater deceleration of PDLGA fibers degradation was observed in case of more hydrophilic PCU (HydroThane), and erosion mechanism changed to surface. Enhancement the affinity of the whole nonwoven to the water, manifested by strong water uptake, facilitated the diffusion processes of both: water and acid degradation by-products, which limited autocatalysis reactions of the hydrolysis of ester bonds. On the other hand, strength tests showed the synergy in the mechanical characteristics of both components. Presented method allows influencing the mechanism and rate of polyester degradation without changing its chemical composition and physical properties, affecting only the physical interactions between the nonwoven and the degradation environment, and thus, on diffusion processes. Obtained partially degradable materials possessed also time prolonged functional properties, compared to the copolyester-only nonwoven itself, thus could be considered as promising for biomedical applications e.g. in drug release systems, implants or surgical meshes for supporting soft tissues.

Fabrication Parameter-Dependent Physico-Chemical Properties of Thiolated Gelatin/PEGDA Interpenetrating Network Hydrogels.

The development of three-dimensional hydrogels using polymeric biomaterials is a key technology for tissue engineering and regenerative medicine. Successful tissue engineering requires the control and identification of the physicochemical properties of hydrogels. Interpenetrating network (IPN) hydrogel was developed using thiolated gelatin (GSH) and poly(ethylene glycol) diacrylate (PEGDA), with the aid of ammonium persulfate (APS) and N,N,N,N'-tetramethylethylenediamine (TEMED) as radical initiators. Each component was prepared in the following concentrations, respectively: 2.5 and 5% GSH (LG and HG), 12.5 and 25% PEGDA (LP and HP), 3% APS/1.5% TEMED (LI), and 4% APS/2% TEMED (HI). IPN hydrogel was fabricated by the mixing of GSH, PEGDA, and initiators in 5:4:1 volume ratios, and incubated at 37°C for 30min in the following 6 experimental formulations: (1) HG-LP-LI, (2) HG-LP-HI, (3) LG-HP-LI, (4) LG-HP-HI, (5) HG-HP-HI, and (6) HG-HP-LI. Herein, the physico-chemical characteristics of IPN hydrogels, including their morphological structures, hydrolytic degradation properties, mechanical properties, embedded protein release kinetics, and biocompatibility, were investigated. The characteristics of the hydrogel were significantly manipulated by the concentration of the polymer, especially the conversion between HP and LP, rather than the concentration of the initiator, and no hydrogel formulation exhibited any toxicity to fibroblast and HaCaTcells. We provide structural-physical relationships of the hydrogels by which means their physical properties could be conveniently controlled through component control, which could be versatilely utilized for various organizational engineering strategies.

Proton conducting membrane based on multifunctional interconnected copolymer containing 4,4′‐diaminodiphenylmethane‐aminoethyl piperazine with sulfonated polyethersulfone membrane for fuel cell application

AbstractThe facile fabrication of proton exchange membrane (PEM) by intermixing of aminoethylpiperazine monomer (AEP), diamino diphenylmethane (DDM) monomer, and AEP combine with varying compositions of DDM (2, 4, and 6 wt%) copolymer with sulfonated polyethersulfone (SPES) and polyamide‐imide (PAI) polymer matrix for fuel cell applications. The intermixing of AEP@DDM copolymer in the SPES/PAI matrix was confirmed by Fourier transform infrared spectroscopy (FTIR) and X‐ray diffraction spectroscopy (XRD) techniques. The physicochemical performance of fabricated PEM was analyzed by water uptake, ion exchange capacity (IEC), swelling ratio, thermal degradation, hydrolytic degradation, chemical and mechanical properties. The intermixing copolymer (AEP@DDM) has significantly suppressed the thermal and hydrolytic deterioration of the PEM. Furthermore, the PAI had noteworthy to improve the thermal and chemical stability of the membranes significantly. The proton conductivity of the SPES/PAI/AEP@DDM (6%) membrane was found to be 5.68 × 10−4 S cm−1 which is 104% higher than the pristine SPES membrane. Besides, the selectivity of SPES/PAI/DDM (6%) was also enhanced up to 80.34% compared to pristine SPES membrane. The inclusion of AEP@DDM in SPES/PAI enhanced the proton conductivity and contributed to the membrane structure's uniformity, as revealed from morphological studies. The AEP@DDM copolymer modification of SPES/PAI membrane has shown good stability, physicochemical property and can be considered as a promising membrane material for fuel cell application.

Preparation, characterization, and in vitro release study of vincristine sulfate-loaded chitosan–polyethylene glycol–oleic acid composites

Vincristine sulfate (VCS) was used in combination with other chemotherapeutic agents for the treatment of a variety of cancers, including acute lymphoblastic leukemia, cervical cancer, and breast cancer. However, rapid release of the drug at the site of specific action was still a challenge for antitumor treatment. Recently, hybrid carriers bearing the versatile properties of each component were promising materials in order to improve the effects of therapeutic drugs. This work aimed to prepare and characterize chitosan (CHS)–polyethylene glycol (PEG)–oleic acid (OA) composites as a carrier for VCS delivery. The structure, thermal stability, and surface morphology of CHS/PEG/OA composites were characterized by using Fourier transform infrared spectroscopy, thermal gravimetric analysis, differential thermal analysis, differential scanning calorimeter, scanning electron microscopy, and atomic force microscopy. Additionally, swelling degree, water uptake capacity, gas permeability, water contact angle, and in vitro hydrolytic degradation properties of the composites were examined in detail. The VCS-loaded CHS/PEG/OA composites were prepared and drug-loading efficiency was evaluated. CPO-2 sample with a loading efficiency of 64.1 ± 0.6% was selected for in vitro release. due to the highest drug loading efficiency. In vitro release behavior was performed in phosphate-buffered saline buffer (pH 7.4). The release of VCS was completed in almost 24 h and the release data were best fitted to Korsmeyer–Peppas model. The release results revealed that CHS/PEG/OA composites with slow-release behavior could be a promising drug carrier for therapeutic drugs such as VCS.

Preparation of biobased poly(propylene 2,5‐furandicarboxylate) fibers: Mechanical, thermal and hydrolytic degradation properties

AbstractIn this work, a fully biobased poly(propylene 2,5‐furandicarboxylate) (PPF) was synthesized from 2,5‐furan dicarboxylic acid (FDCA) and 1,3‐propanediol (1,3‐PDO) via traditional two‐step melting polycondensation. Then, the resultant PPF was characterized with 1H NMR, FTIR, GPC, intrinsic viscosity, TGA, and DSC measurements, respectively. Next, the prepared PPF was melt‐spun into fibers. The morphology and thermal stability of the as‐spun PPF fibers were firstly investigated by SEM and TGA. Furthermore, the mechanical properties of the PPF fibers were evaluated. The results showed that the tensile of the PPF fibers increased with increasing of the draw ratios following gradual decrease of the breaking elongation from 307.1% to 48.9%. In addition, the crystallization ability and the hydrolytic degradation behavior of the as‐spun PPF fibers were investigated in detail as well. The results presented that comparing to traditional fossil‐based poly(trimethylene terephthalate) (PTT) fibers, the PPF fibers exhibited lower crystallinity, however, it displayed a better hydrolytic degradation performance. Based on these results, it confirmed that the PPF fiber based on biomass polymer is a kind of promising environmentally friendly synthetic fiber for potential application in various fields.

3D scaffolding of fast photocurable polyurethane for soft tissue engineering by stereolithography: Influence of materials and geometry on growth of fibroblast cells

Tissue engineering can benefit from the availability of three-dimensional (3D) printing technologies that make it possible to produce scaffolds with complex geometry. Chemical, mechanical, and structural properties should be considered in scaffold design and development since these properties affect cell adhesion, proliferation, and differentiation. To this end, in this study, we developed a series of fast photocuring polyurethanes (PUs), using poly(ε-caprolactone) (PCL) and/or polyethylene glycol (PEG) as microdiols, using a solvent-free method and stereolithography strategy for the fabrication of elastic 3D-printed scaffold. The effects of different diols on the hydrolytic degradation, thermal and mechanical properties, and hydrophilicity of PUs were evaluated. The results showed that PEG-containing PUs had higher degradation rates, and the tensile strength of PU/PCL/PEG was 1.4 and 2 times higher than that of PU/PEG and PU/PCL, respectively. Moreover, the effect of different diols and scaffold geometry on toxicity and cell attachment were studied in vitro. The results of MTT and AlamarBlue assays on dermal fibroblast cells showed high proliferation of printed PU/PCL/PEG scaffold with no sign of cytotoxicity. In addition, compared to cast film PUs, relatively high cell attachment was seen on the surface of printed PU/PCL/PEG even after 4 days. Therefore, 3D printed PU/PCL/PEG showed high applicability in soft tissue engineering, especially for scaffold development.

Phosphoric acid-mediated green preparation of regenerated cellulose spheres and their use for all-cellulose cross-linked superabsorbent hydrogels

With the growing environmental concerns and an emergent demand, a growing attention is turned to eco-friendly superabsorbent hydrogels instead of synthetic counterparts. Hydrogels based on cellulose derivatives can absorb and retain a huge amount of water in the interstitial sites of their structures, stimulating their uses in various useful industrial purposes. In this work, cross-linked superabsorbent composite hydrogel films (CHF) were designed, manufactured and characterized, by taking advantage of the combination of carboxymethyl cellulose (CMC), hydroxyethyl cellulose (HEC) and newly developed regenerated cellulose (RC) spheres. RC with sphere-like shape was successfully prepared using a green method based on cold phosphoric acid-mediated dissolution of microcrystalline cellulose (MCC) followed by regeneration process using water as anti-solvent. Prior to be used, the morphological and structural properties of RC spheres, with an average diameter of 477 ± 270 nm, were examined by SEM, AFM, XRD, FTIR and TGA techniques. CHF crosslinked with citric acid were, in fact, prepared by solvent casting method with different RC weight fractions (i.e. 0, 2.5, 5, 10 and 15 wt%), then the crosslinking reaction was triggered by thermal treatment at 80 °C during 8 h. Prepared CHF were then characterized in terms of their structural, thermal, tensile and transparency properties. Swelling tests were carried at three different aqueous media (i.e. with a pH = 3, 6.4 or 11) to evaluate the water retention capacity of hydrogel films, as well as, the pH effect on their swelling and hydrolytic degradation properties. Collected results reveal that CHF with low RC content (i.e. RC weight fraction of 2.5 or 5 wt%) have the best tensile and swelling properties, with a tensile strength and a swelling capacity (at pH = 6.4) up to 95 MPa and 4000%, respectively.

Biodegradable, Flexible, and Transparent Conducting Silver Nanowires/Polylactide Film with High Performance for Optoelectronic Devices.

As a synthetic renewable and biodegradable material, the application of polylactide (PLA) in the green flexible electronics has attracted intensive attention due to the increasingly serious issue of electronic waste. Unfortunately, the development of PLA-based optoelectronic devices is greatly hindered by the poor heat resistance and mechanical property of PLA. To overcome these limitations, herein, we report a facile and promising route to fabricate silver nanowires/PLA (AgNW/PLA) film with largely improved properties by utilizing the stereocomplex (SC) crystallization between poly(L-lactide) (PLLA) and poly(D-lactide) (PDLA). Through embedding the AgNW networks into the PLLA:PDLA blend matrix via a transfer method, the AgNW/PLLA:PDLA film with both high transparency and excellent conductivity was obtained. Compared with the AgNW/PLLA film, the formation of SC crystallites in the composites matrix could significantly enhance not only heat resistance but also mechanical strength of the AgNW/PLLA:PDLA film. Exceptionally, the AgNW/PLLA:PDLA film exhibited superior flexibility and could maintain excellent electrical conductivity stability even under the condition of 10,000 repeated bending cycles and 100 tape test cycles. In addition, the organic light-emitting diodes (OLEDs) with the AgNW/PLLA:PDLA films as electrodes were successfully fabricated in this work for the first time and they exhibited highly flexible, luminous, as well as hydrolytic degradation properties. This work could provide a low-cost and environment-friendly avenue towards fabricating high-performanced PLA-based biodegradable electronics.

Preparation and study on the optical, mechanical, and antibacterial properties of polylactic acid/ZnO/TiO2 shared nanocomposites

In this research, first, ZnO nanorods were synthesized by hydrothermal method and characterized in terms of morphological and structural properties by means of field emission scanning electron microscopy, Fourier transform infrared, and X-ray diffraction techniques. Subsequently, polylactic acid/ZnO, polylactic acid/TiO2, and polylactic acid/ZnO/TiO2 nanocomposites with different percentages of nanoparticles and two different types of ZnO morphologies were prepared and their microstructural, optical, mechanical, hydrolytic degradation, and antibacterial properties were investigated. Field emission scanning electron microscopy results of polylactic acid/ZnO and polylactic acid/TiO2 samples showed a proper dispersion and nanoparticle distribution for low percentages (up to 5 wt%) and increased aggregation for the higher percentages. Besides, a large increase in the aggregation tendency was observed for combined nanoparticles (polylactic acid/ZnO/TiO2 nanocomposites). Results of the tensile test, the UV–Vis absorption tests, and the hydrolytic degradation tests of the samples showed an enhanced mechanical (approximately 55% increase in the presence of 3–5 wt% of nanoparticles) and light absorption and degradation (approximately 85% increase in the presence of 3–10 wt% of nanoparticles) for the polylactic acid by incorporating nanoparticles. It was also observed that, in addition to the quality of dispersion and distribution of nanoparticles in the polymeric matrix, the type of morphology of nanoparticles can contribute to the improvement of these properties. The cylindrical morphology of ZnO played a greater role on improving the polylactic acid mechanical properties compared to the spherical ZnO morphology (approximately 20%). On the contrary, the increased polylactic acid optical properties and degradation with ZnO spherical morphology were more pronounced (approximately 60%). Interestingly, when both ZnO and TiO2 were added, a synergistic effect in the case of UV-shielding and degradation rate and alternatively, a detrimental effect on the mechanical properties were detected. (The polylactic acid optical properties increased by about 17% and its degradation more than doubled.) Furthermore, the antibacterial activity of polylactic acid was investigated against the two Gram-positive Listeria monocytogenes and Gram-negative bacteria Escherichia coli by incorporating nanoparticles. The results indicated that as the nanoparticle percentage increases, the antibacterial activity steadily increases.

Methacrylated Hyaluronic Acid–Based Hydrogels Maintain Stemness in Human Dental Pulp Stem Cells

2-Aminoethyl methacrylate (AEMA)–modified hyaluronic acid (HA) hydrogels with tunable swelling, degradation, and rheological properties were developed to maintain the native spherical and stemness of human dental pulp stem cells (DPSCs). Two molecular weights (MW) of HA, 18 and 270 kDa, and 25% degree of AEMA substitution were used to synthesize the HA macromers and hydrogels. The HA macromers were characterized by 1H NMR, and the AEMA-HA hydrogels were synthesized by UV polymerization. The swelling, hydrolytic degradation, and rheological properties of the hydrogels strongly depended on the MW of HA. The degradation rate decreased and the storage modulus increased with the increase in the MW of HA. The storage modulus of the hydrogels decreased with degradation of the hydrogels. The hydrogels were not cytotoxic to DPSCs evidenced by MTT assay, Hoechst 33342 live cell staining, and propidium iodide dead cell staining. The hydrogels maintained the native spherical morphology and stemness of DPSCs when the hydrogels’ storage moduli were in the ranges of 486–681 Pa. In contrast, DPSCs grown on 2D cell culture substrates showed a flat and elongated shape and could not maintain their native spherical shape. The hydrogels increased the expression of the stemness including NANOG and SOX2 of DPSCs (3 and 24 folds, respectively) when their storage modulus was 681.41 ± 92.81 Pa in comparison with DPSCs grown on 2D cell culture plates. The designed AEMA-HA hydrogels mimic the in vivo 3D environment to grow DPSCs. Thus, they appear to have great potential for clinical applications in regenerative medicine and other therapeutic remedies after further optimization in the future. Regenerative medicine is a translational approach that offers the possibility to replace or heal the diseased or damaged tissues caused by trauma, age, infection, cancer, or inherited defects. Such reinstatement of the functionality or healing of the damaged cells or tissues often includes the combination of numerous strategies including the use of biomaterials/scaffolds, stem cells, growth factors, and small molecules. In this study, we used hyaluronic acid (HA), a naturally occurring polysaccharide biopolymer commonly found in the extracellular matrix of connective tissues, to synthesize 3D hydrogel scaffolds for growing human dental pulp stem cells (DPSCs). We evaluated the effects of the molecular weight of HA, and the swelling, degradation, and rheological properties of the hydrogels on maintaining the native spherical and stemness of DPSCs for future therapeutic applications including regenerative medicine.

Nanoparticulate delivery of irinotecan active metabolite (SN38) in murine colorectal carcinoma through conjugation to poly (2-ethyl 2-oxazoline)-b-poly (L-glutamic acid) double hydrophilic copolymer

SN-38 is the active metabolite of irinotecan, an FDA-approved chemotherapeutic agent indicated for colorectal carcinoma, which would not be clinically applicable due to its very poorly soluble and hydrolytic degradation properties. To overcome these limitations, it was proposed to conjugate SN38 to residing carboxylic acid residues in poly (2-ethyl 2-oxazoline) block poly (L-glutamic acid), inducing nano-assembly in aqueous medium. Following a series of reactions including poly (2-ethyl oxazoline) macro-initiated ring opening polymerization of N-carboxyanhydride, deprotection of benzyl group and chemical conjugation of SN38 via biodegradable ester linkage, the as-synthesized product was characterized by dynamic light scattering, ζ potential and transmission electron microscopy. The resulting particles presented about 90% loading efficiency with a mean size of 90 nm. Upon incubation with colorectal carcinoma CT26 cell line, higher association of SN-38 fluorescence and significantly more specific cytotoxicity was noticed for the SN38 conjugated particles than free drug. Therapeutic applicability of the as-synthesized product was evaluated in CT26 allograft tumor model in BALB/c mice, showing superior efficiency of the SN38 conjugated particles particularly in tumors with sizes larger than 200 mm3 than parent irinotecan and reduced mortality rate by 2.5 times. Conclusively, the poly (2-ethyl 2-oxazoline) decorated nano-conjugates of poly (L-glutamic acid) and SN38 can be regarded as a novel and potentially efficient drug delivery system for advanced colorectal carcinoma.

A green physical approach to compatibilize a bio-based poly (lactic acid)/lignin blend for better mechanical, thermal and degradation properties

The poly (lactic acid) (PLA) and lignin (LG) are promising candidates to develop green plastic. However, the blending of lignin with PLA leads to incompatible blend with poor mechanical and thermal properties. Hence, in the present work, a green and simple approach was employed to make PLA/LG compatible blend with high lignin percentage (5 and 20%). The E-beam irradiated lignins having different absorbed dosages were blended with two different percentages 5 and 20 with PLA in the presence of 3 phr triallyl isocyanurate (TAIC). FTIR and DSC studies have confirmed the formation of PLA-TAIC-Lignin crosslinked structures which act as an interface between the dispersed lignin phase and PLA matrix and hence improved their compatibility in the resulting blend. The compatibility of resulting blends was further validated by the morphology study, Glass transition temperature (Tg) behavior of PLA/LG blends and by observing the significant improvement in the mechanical, thermal and hydrolytic degradation properties.

Performance evaluation of poly (l-lactide-co-D, l-lactide)/poly (acrylic acid) blends and their nanofibers for tissue engineering applications

Poly (l-lactide-co-D, l-lactide) (PLDLLA) is a biodegradable polymer predominantly used in biomedical applications. Despite unprecedented characteristics of PLDLLA, its wettability, mechanical properties, degradation, and cell attachment are main issues to improve. In this work, different blend films based on PLDLLA/poly (acrylic acid) (PAAc) are prepared to evaluate their miscibility, hydrophilicity, hydrolytic degradation and mechanical properties. For this purpose, a series of experiments such as DSC alongside SEM, water contact angle (WCA)/water up-take, weight measurements in phosphate buffer saline (PBS) and NaOH as well as tensile test are carried out. The DSC and SEM results show a miscibility for the blends, and hence by increasing PAAc, the WCA values and degradation rates are decreased and increased, respectively. Moreover, the degradation mechanisms of the blend samples follow surface/bulk erosion and bulk process in the alkaline and PBS environments, respectively. Subsequently, PLDLLA and its blends are electrospun to prepare nanofibrous samples, thereby assessing their cytotoxicity and cell viability by the use of thiazolyl blue assay and acridine orange/ethidium bromide staining, respectively. The in vitro SNL 76/7 fibroblast cells cultivation onto the surface of the blend with 10% wt. of PAAc revealed that this sample is a promising candidate for tissue engineering applications.