Aliphatic polyesters are the most common type of biodegradable synthetic polymer used in many pharmaceutical applications nowadays. This report describes the ring-opening polymerization (ROP) of ...l-lactide (L-LA), ε-caprolactone (CL) and glycolide (Gly) in the presence of a simple, inexpensive and convenient PEG200-BiOct
catalytic system. The chemical structures of the obtained copolymers were characterized by
H- or
C-NMR. GPC was used to estimate the average molecular weight of the resulting polyesters, whereas TGA and DSC were employed to determine the thermal properties of polymeric products. The effects of temperature, reaction time, and catalyst content on the polymerization process were investigated. Importantly, the obtained polyesters were not cyto- or genotoxic, which is significant in terms of the potential for medical applications (e.g., for drug delivery systems). As a result of transesterification, the copolymers obtained had a random distribution of comonomer units along the polymer chain. The thermal analysis indicated an amorphous nature of poly(l-lactide-
-ε-caprolactone) (PLACL) and a low degree of crystallinity of poly(ε-caprolactone-
-glycolide) (PCLGA,
= 15.1%), in accordance with the microstructures with random distributions and short sequences of comonomer units (
= 1.02-2.82). Significant differences in reactivity were observed among comonomers, confirming preferential ring opening of L-LA during the copolymerization process.
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•3D printed / electrospun fibers porous scaffolds (3D/E) of PLCL and PLGA were designed and developed for tissue regenerative treatments.•The novel plasma-treated 3D/E scaffolds of ...PLCL and PLGA were successfully prepared using a nitrogen-argon plasma system (N2/Ar).•Treated 3D/E scaffolds lead to enhance hydrophilic properties and surface roughness, which was beneficial to enhance biological performance.•This study suggests a simple and fast way of printing and plasma technology to design, fabricate and modify scaffolds for tissue regenerative treatments.
In this study, two-component, morphologically composite scaffolds consisting of a 3D-printed component and an electrospun fiber component were fabricated and treated with a nitrogen-argon (N2-Ar) plasma to enhance their surface properties. The 3D-printed component provided mechanical strength, while the electrospun fibrous component acted as a mimic to the extracellular matrix to improve cell-substrate interactions. Two biodegradable polyesters, poly(L-lactide-co-ε-caprolactone) (PLCL) and poly(L-lactide-co-glycolide) (PLGA), were used to create the scaffolds. The resulting 3D/E/N2-Ar scaffolds were characterized in terms of surface properties (morphology, chemical compositions, wettability, roughness, crystallinity), degradation, mechanical properties, and cell cytotoxicity, cell attachment and proliferation, LDH release and cell apoptosis. Results showed that the plasma treatment significantly increased the surface roughness, wettability, and hydrophilicity of the scaffolds. The 3D-printed component provided sufficient mechanical support, while the electrospun fiber component promoted cell attachment and proliferation. Following plasma treatment, the water contact angle of the scaffolds was greatly reduced from 124.0 ± 1.8° (PLCL) and 119.6 ± 1.4° (PLGA), to 0° and persisted even after 168 days. Human Schwann cells (SCs) showed excellent viability on both 3D/E/N2-Ar and 3D/E scaffolds were in excess of 95%. Cells cultivated on the 3D/E/N2-Ar scaffolds, with higher surface roughness, displayed significant increase in attachment and proliferation and a higher presence of healthy cells when compared with untreated 3D/E scaffolds. Both PLCL and PLGA scaffolds showed potential for use in biomedical applications. Although PLGA performed slightly better in terms of cell behavior, PLCL exhibited a slower degradation rate and higher tensile strain. These results demonstrate the potential of these designed scaffolds to support cell regeneration in clinically relevant devices such as nerve guide conduits and nerve protectant wraps.
Poly(l‐lactide‐co‐ε‐caprolactone) (PLCL) is a biodegradable elastomer, but its applications are limited due to weak mechanical strength and processability. To overcome these limitations, PLCL was ...modified by incorporating polycaprolactone (PCL) and plasticizing with polyethylene glycol (PEG) for microinjection molding. The molded PLCL/PCL/PEG parts were characterized in terms of thermal properties, rheological properties, and mechanical properties. The results indicate that increasing the PCL content from 20% to 50% effectively enhanced the mechanical properties of the blend. Moreover, the addition of PEG enhanced the processability of the blends in the microinjection molding process with negligible impacts on their mechanical properties. PEG plasticizes the PLCL/PCL blend by reducing the intermolecular interactions of the blend, and the effect is more pronounced with a PEG of lower molecular weight.
PLCL is reinforced by PCL and plasticized by PEG to realize microinjection molding.
A low molecular weight hydrazide compound, tetramethylenedicarboxylic di (2‐hydroxybenzohydrazide) (TMBH), greatly improves the crystallization rate and crystallinity of poly(l‐lactide) (PLLA). The ...nucleating efficiency of TMBH on the crystallization of PLLA exhibits obvious concentration dependence, which increases first and then decreases slightly with the increase of TMBH loading, reaching a maximum at 0.3 wt%. Time‐resolved Fourier transform infrared spectroscopy spectra indicate that the formation of skeletal conformational ordering structure of PLLA has been accelerated in the presence of TMBH, which can act as efficient precursors speeding up both the nucleation of PLLA on TMBH surface and the formation of intrachain 103 helix structure. The possible hydrogen bonding interaction between the OH or NH groups in TMBH and the CO groups in PLLA backbones is supposed to be an important factor, which promotes the migration of PLLA chains to TMBH crystallites and the emergence of interchain interactions as well as the conformational ordering.
The crystallization rate of poly(l‐lactide) (PLLA) has been enhanced effectively by the addition of a hydrazide compound, tetramethylenedicarboxylic di (2‐hydroxybenzohydrazide) (TMBH). It has been revealed that TMBH can promote the skeletal conformational ordering of PLLA via possible hydrogen bonding interaction, which thus accelerates the nucleation kinetics of PLLA and the subsequent formation of 103 helix structure.
Osteosynthesis absorbable materials made of uncalcined and unsintered hydroxyapatite (u-HA) particles, poly-l-lactide (PLLA), and u-HA/PLLA are bioresorbable, and these plate systems have feasible ...bioactive osteoconductive capacities. However, their strength and stability for fixation in mandibular subcondylar fractures remain unclear. This in vitro study aimed to assess the biomechanical strength of u-HA/PLLA bioresorbable plate systems after internal fixation of mandibular subcondylar fractures. Tensile and shear strength were measured for each u-HA/PLLA and titanium plate system. To evaluate biomechanical behavior, 20 hemimandible replicas were divided into 10 groups, each comprising a titanium plate and a bioresorbable plate. A linear load was applied anteroposteriorly and lateromedially to each group to simulate the muscular forces in mandibular condylar fractures. All samples were analyzed for each displacement load and the displacement obtained by the maximum load. Tensile and shear strength of the u-HA/PLLA plate were each approximately 45% of those of the titanium plates. Mechanical resistance was worst in the u-HA/PLLA plate initially loaded anteroposteriorly. Titanium plates showed the best mechanical resistance during lateromedial loading. Notably, both plates showed similar resistance when a lateromedially load was applied. In the biomechanical evaluation of mandibular condylar fracture treatment, the u-HA/PLLA plates had sufficiently high resistance in the two-plate fixation method.
Summary
Poly(l‐lactide) (PLL) has been blended with a polycaprolactone‐based thermoplastic polyurethane (TPU) elastomer as a toughening agent and a poly(l‐lactide‐co‐caprolactone) (PLLCL) copolymer ...as a compatibilizer. Both 2‐component (PLL/TPU) and 3‐component (PLL/TPU/PLLCL) blends were prepared by melt mixing, characterized, hot‐pressed into thin sheets and their tensile properties tested. The results showed that, although the TPU could toughen the PLL, the blends were largely immiscible leading to phase separation. However, addition of the PLLCL copolymer improved blend compatibility. The best all‐round properties were found for the 3‐component blend of composition PLL/TPU/PLLCL = 90/10/10 parts by weight.
Three kinds of high molecular weight polymers were synthesized by ring-opening polymerization with various monomer feeding ratios (named as PLLA, PLCL 95/5 and PLGC 80/15/5, respectively). Then ...oriented monofilament was produced through melt-extrusion and tensile orientation based on each kind of polymer. In vitro degradation properties of the monofilaments were studied over a range of degradation time from 1 to 21 days at 60 °C by using SEM, GPC, DSC, XRD and tensile test. Degradation results showed that the mass loss, Tg and morphology integrity of the PLLA monofilament basically remained unchanged, and partial degradation in amorphous region emerged with slight increase of crystallinity. For the PLCL 95/5 monofilament, the crystallinity was increased and the monofilament was fractured at 14 days accompanying with obvious decrease of the mass and Tm, indicating that most part of the amorphous region was degraded. Apparently, the PLGC 80/15/5 monofilament showed the fastest degradation rate with considerable mass loss and decrease of Tg. The amorphous region was degraded sharply in the early stage due to its good water absorbability and lower structural regularity, and the initially-formed crystalline region was degraded slowly later evidenced from the change of crystallinity and it was fractured at 3 days. The accelerated effects calculated according to the first-order kinetic model demonstrated that the PLCL 95/5 monofilament was degraded 2.5 times faster than pure PLLA and the PLGC 80/15/5 monofilament was degraded 7.5 times faster than PLLA. These were nearly consistent with those based on η (2.5 and 6.9 times respectively). The comparative study of in vitro degradation behavior of PLLA-based copolymer monofilaments would provide useful information for controlling the monomer composition of PLLA-based materials with specific degradation requirements.
•Three kinds of high molecular weight polymers were synthesized with various monomer feeding ratios.•A comparative study of in vitro degradation behavior of the PLLA-based copolymer monofilaments was conducted.•The PLGC 80/15/5 monofilament showed the most rapid degradation behavior owning to its higher hydrophilicity.•The accelerated effects were applied to analyze the relationship between the monomer ratio and the degradation rate.
The ability to control nanostructure shape and dimensions presents opportunities to design materials in which their macroscopic properties are dependent upon the nature of the nanoparticle. Although ...particle morphology has been recognized as a crucial parameter, the exploitation of the potential shape-dependent properties has, to date, been limited. Herein, we demonstrate that nanoparticle shape is a critical consideration in the determination of nanocomposite hydrogel properties. Using translationally relevant calcium-alginate hydrogels, we show that the use of poly(L-lactide)-based nanoparticles with platelet morphology as an adhesive results in a significant enhancement of adhesion over nanoparticle glues comprised of spherical or cylindrical micelles. Furthermore, gel nanocomposites containing platelets showed an enhanced resistance to breaking under strain compared to their spherical and cylindrical counterparts. This study opens the doors to a change in direction in the field of gel nanocomposites, where nanoparticle shape plays an important role in tuning mechanical properties.
Simultaneously improving the toughness and heat resistance of poly(l-lactide) (PLLA) is significant for expanding biodegradable materials' application range. In this work, reactive compatibilizers ...containing PBS and PLLA (PBS-St-GMA-PLLA (SGL)) or poly(d-lactide) (PBS-St-GMA-PDLA (SGD)) were synthesized and incorporated in blends of commercial PLLA and PBS as compatibilizers. The in situ formation of stereocomplex (SC) crystallites of PLA at the interface of PLLA and PBS was successfully achieved through simple melt blending. The effects of SC crystallites, amount of compatibilizers on morphology, crystallization behavior, mechanical properties, heat resistance and degradability properties of PLLA/PBS blends were studied. Morphological evolution showed that SGL and SGD significantly improved the compatibility of PLLA/PBS blends. After incorporating 5% SGD, the elongation at break and notched impact strength of PLLA/PBS blends with SC crystallites reached 273% and 34 kJ/m2, respectively, 12 and 5 times than that of pristine PLLA/PBS blends. As compared with PLLA/PBS/SGL blends that cannot form SC crystallites, the tensile strength of the blends was effectively improved by the presence of SC crystallites, ascribing to improved interfacial compatibility and remarkable acceleration in matrix crystallization kinetics of PLLA. Consequently, the blends containing 5% SGD exhibited excellent heat resistance (E′80°C > 680 MPa) after brief annealing, which far exceeded the PLLA or PLLA/PBS blends. This work may provide a feasible way to prepare PLLA-based materials with excellent comprehensive properties by the formation of SC crystallites.
Supertoughened and heat-resistant biodegradable PLLA/PBS blends were prepared by adding a reactive compatibilizer containing PDLA and PBS. A 82.7 and 8.6-fold increase in elongation at break and impact strength was achieved upon incorporating 5 wt% reactive compatibilizers due to the presence of small amount of interface-localized SC crystallites in PLLA/PBS blends. Display omitted
•Reactive compatibilizers containing PDLA and PBS were prepared through simple melt blending and incorporated in blends of commercial PLLA and PBS as compatibilizer.•Interface-localized SC crystallites were formed between the grafted PDLA chains and PLLA matrix under shear, which further improved interfacial adhesion and induced morphological evolution.•After incorporation of 5% reactive compatibilizers, the elongation at break and notched impact strength of PLLA/PBS blends with SC crystallites reached 273% and 34 kJ/m2, respectively, which were 12 and 5 times than that of neat PLLA/PBS blend.•SC crystallites can act as nucleation sites, resulting in greatly accelerated crystallization rate and enhanced heat resistance (E'80° C >680 MPa) after annealing.
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