Chemical modifications of PLA through copolymerization

A coating machine for coating filaments with bioactive nanomaterials for extrusion 3D printing

Extrusion printing based on biocompatible filaments offers a wide variety of targeted medical and dental applications in the area of personalized medicine, if combined with bioactive nanomaterials. However, this requires filament to be coated with bioactive nanomaterial. This study introduces a concept of a machine to coat filament with bioactive nanomaterials and its application. A machine was constructed with modules manufactured using additive manufacturing. A filament spool of polylactide (PLA) or glycol-modified polyethylene terephthalate (PETG) was transported through a copper tube, with the outer surface of the filament heated to the appropriate glass transition temperature to incorporate added nanomaterials such as nano-hydroxyapatite (nHA) or nano-fluorapatite(nFA). Coatings with nHA led to an increase in diameter of around 3 μm, while coatings with nFA increased the diameter by 4 μm. Printing of cubes with a standard extrusion printer platform using PLA or PETG filaments with added nHA or nFA has been successfully carried out. Scanning electron microscope (SEM) images of coated filaments and printed cubes showed an irregular distribution of nHA or nFA, which could be verified by energy dispersive X-ray analysis (EDX). Adding and adjusting bioactive nanomaterials to filament with a coating machine for filament proved to generate printable filaments. With the wide range of possible applications by different nanomaterials it is anticipated that extrusion printing can cover needs for personalized medicine and dentistry.

Raspberry-like PLA/PGS biodegradable microparticles with urethane linkages: Unlocking tailored release of magnesium ions and oxygen for bone tissue engineering

Designing biodegradable microparticles with finely controlled release properties for tissue engineering systems remains a significant scientific challenge. This study introduces a novel approach by fabricating urethane-linked PLA/PGS microparticles loaded with magnesium peroxide. The microparticles offer potential applications in bone tissue engineering due to their ability to provide a controlled release of oxygen and magnesium ions while maintaining physiological pH. The PGS pre-polymer was synthesized via polycondensation and characterized using FTIR, 1H NMR, and GPC. Microparticle morphology transformed from smooth to raspberry-like upon incorporation of PGS, as observed by SEM. Microparticle size was tuned by varying PGS and PLA concentrations. FTIR analysis confirmed the successful formation of urethane links within the microparticles. MgO2-loaded PLA/PGS microparticles exhibited sustained release of dissolved oxygen and magnesium ions for 21 days while maintaining physiological pH better than PLA microparticles. Cell viability assays confirmed microparticle cytocompatibility, and ALP and Alizarin red assays demonstrated their ability to induce osteogenic differentiation. These findings highlight the potential of pH-controlled MgO2-loaded microparticles as an effective system for bone tissue engineering. In conclusion, this study presents a novel approach to designing biodegradable microparticles with adjustable release properties for bone tissue engineering. The urethane-based MgO2-loaded microparticles provide controlled release of oxygen and magnesium ions and regulate the environment's pH, making them a promising system for bone tissue engineering applications.

Polylactide-Based Nonisocyanate Polyurethanes: Preparation, Properties Evaluation and Structure Analysis

This study investigated the successful synthesis and characterization of nonisocyanate polyurethanes (NIPUs) based on polylactide. The NIPUs were synthesized by a condensation reaction of oligomers with hard segments (HSs) and synthesized carbamate-modified polylactic acid containing flexible segments (FSs). The oligomers with HSs were prepared from phenolsulfonic acid (PSA) or a mixture of PSA and hydroxynaphthalenesulfonic acid (HNSA), urea and formaldehyde. The mixing of oligomeric compounds with different amounts of formaldehyde was carried out at room temperature. Obtained NIPU samples with different hard segment content were tested for their mechanical and thermal properties. The tensile strength (TS) of all NIPU samples increased with an increasing amount of HSs, attaining the maximum value at an HS:FS ratio of 1:3. Samples prepared from PSA and HNSA showed higher tensile strength (TS) without significant change in elongation at break compared to the samples based only on PSA. Thermogravimetric analysis data indicated an absence of weight loss for all samples below 100 °C, which can be considered a safe temperature for using NIPU materials. Maximum degradation temperatures reached up to 385 °C. Fourier transform infrared spectroscopy results confirmed the existence of expected specific groups as well as the chemical structure of the prepared polyurethanes. DSC analysis showed the existence of two characteristic phase transitions attributed to the melting and crystallization of hard segments in the NIPU samples.

Improvement of the mechanical and shape memory properties in polylactide/polyethylene glycol blends by reactive graphene oxide

The widespread application of biodegradable polylactide (PLA) is hindered by its brittleness. Polyethylene glycol (PEG) is commonly utilized as a plasticizer because of its favorable compatibility with PLA. However, the incorporation of PEG considerably diminishes the tensile strength of PLA. To address this issue, reactive isocyanate-modified graphene oxide (mGO) was synthesized and used as an enhancer in PLA/PEG blends. By virtue of the reaction between the isocyanate group in mGO and the terminal hydroxyl groups of PLA and PEG, graphene-based polyurethane (PU) in-situ formed and enhanced the interface between GO and the matrix. Consequently, the PLA/PEG/mGO composites exhibit simultaneously improved tensile and impact strengths, achieving an increase of 20.6% and 29.4%, respectively, compared to PLA/PEG blends. Moreover, the in situ formed PU reduces the relaxation time of the molecule motion and improved the entanglement density, thereby improving the shape-memory recovery rate and final recovery degree of the composites. This work provides a facile method to simultaneously improve the dispersion of GO and enhance its interface with polymer, thereby supplying well comprehensive properties of PLA and extending the applications of biodegradable polymers.

Advances, challenges, and prospects for surgical suture materials

As one of the long-established and necessary medical devices, surgical sutures play an essentially important role in the closing and healing of damaged tissues and organs postoperatively. The recent advances in multiple disciplines, like materials science, engineering technology, and biomedicine, have facilitated the generation of various innovative surgical sutures with humanization and multi-functionalization. For instance, the application of numerous absorbable materials is assuredly a marvelous progression in terms of surgical sutures. Moreover, some fantastic results from recent laboratory research cannot be ignored either, ranging from the fiber generation to the suture structure, as well as the suture modification, functionalization, and even intellectualization. In this review, the suture materials, including natural or synthetic polymers, absorbable or non-absorbable polymers, and metal materials, were first introduced, and then their advantages and disadvantages were summarized. Then we introduced and discussed various fiber fabrication strategies for the production of surgical sutures. Noticeably, advanced nanofiber generation strategies were highlighted. This review further summarized a wide and diverse variety of suture structures and further discussed their different features. After that, we covered the advanced design and development of surgical sutures with multiple functionalizations, which mainly included surface coating technologies and direct drug-loading technologies. Meanwhile, the review highlighted some smart and intelligent sutures that can monitor the wound status in a real-time manner and provide on-demand therapies accordingly. Furthermore, some representative commercial sutures were also introduced and summarized. At the end of this review, we discussed the challenges and future prospects in the field of surgical sutures in depth. This review aims to provide a meaningful reference and guidance for the future design and fabrication of innovative surgical sutures. STATEMENT OF SIGNIFICANCE: This review article introduces the recent advances of surgical sutures, including material selection, fiber morphology, suture structure and construction, as well as suture modification, functionalization, and even intellectualization. Importantly, some innovative strategies for the construction of multifunctional sutures with predetermined biological properties are highlighted. Moreover, some important commercial suture products are systematically summarized and compared. This review also discusses the challenges and future prospects of advanced sutures in a deep manner. In all, this review is expected to arouse great interest from a broad group of readers in the fields of multifunctional biomaterials and regenerative medicine.

Synthesis and Characterization of Functionalized Polylactides Containing Acetal Units

New functionalized lactide copolymers containing acetal units were prepared for the first time in a controlled manner that enabled the regulation of the number of reactive groups introduced into the polyester chain. The presence of functional groups in the copolymer backbone provided chemical modification sites, and the nature of the acetal unit affected the material degradability. First, paraformaldehyde was reacted with selected diols containing reactive pendant groups (3-allyloxypropane-1,2-diol and 3-chloropropane-1,2-diol), which was catalyzed by p-toluenesulfonic acid, to synthesize new cyclic acetals with different functionalities (allyl- or chloro-). In addition, using butane-1,4-diol, a nonfunctionalized seven-membered cyclic acetal (dioxepane) was obtained for comparative studies. In the next step, the prepared cyclic acetals were used for cationic copolymerization with lactide in the presence of glycol as an initiator and triflic acid as a catalyst. Different temperatures (-15, 2, and 30 °C) and copolymerization times (24, 48, 72, and 192 h) were investigated to produce copolyesters with variable contents of acetal units in the range of 5-27%. The copolymers' structure and molar masses were carefully investigated using 1H, 13C NMR, 2D NMR, and size-exclusion chromatography. Moreover, the ability of functionalized copolymers to perform post modifications was also proven by the reaction with sodium azide and propanethiol. Finally, we speculate that structurally diverse groups can be attached to the copolyester chain, fine-tuning the on-demand properties, which could rapidly expand the library of polylactide-based materials.

Poly(1,3-Propylene Glycol Citrate) as a Plasticizer for Toughness Enhancement of Poly-L-Lactic Acid

Despite the unique features of poly-L-lactic acid (PLLA), its mechanical properties, such as the elongation at break, need improvement to broaden its application scope. Herein, poly(1,3-propylene glycol citrate) (PO3GCA) was synthesized via a one-step reaction and evaluated as a plasticizer for PLLA films. Thin-film characterization of PLLA/PO3GCA films prepared via solution casting revealed that PO3GCA shows good compatibility with PLLA. The addition of PO3GCA slightly improves the thermal stability and enhances the toughness of PLLA films. In particular, the elongation at break of the PLLA/PO3GCA films with PO3GCA mass contents of 5%, 10%, 15%, and 20% increases to 172%, 209%, 230%, and 218%, respectively. Therefore, PO3GCA is promising as a plasticizer for PLLA.

Bio-Based Poly(lactic acid)/Poly(butylene sebacate) Blends with Improved Toughness

A series of poly(butylene sebacate) (PBSe) aliphatic polyesters were successfully synthesized by the melt polycondensation of sebacic acid (Se) and 1,4-butanediol (BDO), two monomers manufactured on an industrial scale from biomass. The number average molecular weight (M_n) in the range from 6116 to 10,779 g/mol and the glass transition temperature (T_g) of the PBSe polyesters were tuned by adjusting the feed ratio between the two monomers. Polylactic acid (PLA)/PBSe blends with PBSe concentrations between 2.5 to 20 wt% were obtained by melt compounding. For the first time, PBSe’s effect on the flexibility and toughness of PLA was studied. As shown by the torque and melt flow index (MFI) values, the addition of PBSe endowed PLA with both enhanced melt processability and flexibility. The tensile tests and thermogravimetric analysis showed that PLA/PBSe blends containing 20 wt% PBSe obtained using a BDO molar excess of 50% reached an increase in elongation at break from 2.9 to 108%, with a negligible decrease in Young’s modulus from 2186 MPa to 1843 MPa, and a slight decrease in thermal performances. These results demonstrated the plasticizing efficiency of the synthesized bio-derived polyesters in overcoming PLA’s brittleness. Moreover, the tunable properties of the resulting PBSe can be of great industrial interest in the context of circular bioeconomy.

Polylactide Perspectives in Biomedicine: From Novel Synthesis to the Application Performance

The incessant developments in the pharmaceutical and biomedical fields, particularly, customised solutions for specific diseases with targeted therapeutic treatments, require the design of multicomponent materials with multifunctional capabilities. Biodegradable polymers offer a variety of tailored physicochemical properties minimising health adverse side effects at a low price and weight, which are ideal to design matrices for hybrid materials. PLAs emerge as an ideal candidate to develop novel materials as are endowed withcombined ambivalent performance parameters. The state-of-the-art of use of PLA-based materials aimed at pharmaceutical and biomedical applications is reviewed, with an emphasis on the correlation between the synthesis and the processing conditions that define the nanostructure generated, with the final performance studies typically conducted with either therapeutic agents by in vitro and/or in vivo experiments or biomedical devices.

Facile Preparation of Hydrophobic PLA/PBE Micro-Nanofiber Fabrics via the Melt-Blown Process for High-Efficacy Oil/Water Separation

Polylactic acid (PLA) micro-nanofiber fabrics with a large specific surface area and excellent biodegradability are commonly used in oil/water separation; however, challenges remain due to their poor mechanical properties. Herein, a thermoplastic polylactic acid/propylene-based elastomer (PLA/PBE) polymer was prepared by blending PLA with PBE. Then, PLA/PBE micro-nanofiber fabrics were successfully prepared using a melt-blown process. The results show that the PLA/PBE micro-nanofiber fabric has a three-dimensional porous structure, improving the thermal stability and fluidity of the PLA/PBE blended polymers. The PLA/PBE micro-nanofiber fabric demonstrated a significantly reduced average fiber diameter and an enhanced breaking strength. Moreover, the water contact angle of the prepared samples is 134°, which suggests a hydrophobic capacity. The oil absorption rate of the fabric can reach 10.34, demonstrating excellent oil/water separation performance. The successful preparation of PLA/PBE micro-nanofiber fabrics using our new method paves the way for the large-scale production of promising candidates for high-efficacy oil/water separation applications.

A New Approach to The Synthesis of Polylactide/Polyacrylonitrile Block Copolymers

As a result of the search for alternatives to the known methods for the synthesis of PLA/vinyl polymer block copolymers, a new approach based on the “iniferter” concept was demonstrated in this article. In this approach, the introduction of a group that was capable of forming radicals and initiating radical polymerization into the polylactide (PLA) chain was conducted. Then, the obtained functional PLA was heated in the presence of a radically polymerizable monomer. The tetraphenylethane (TPE) group was chosen as a group that could dissociate to radicals. PLA with a TPE group in the middle of the chain was prepared in several steps as follows: (1) the synthesis of 4-(2-hydroxyethoxy)benzophenone (HBP-ET); (2) the polymerization of lactide, which was initiated with HBP-ET; and (3) the coupling of HBP-ET chains under UV radiation to form TPE-diET_PLA. A “macroiniferter”, i.e., TPE-diET_PLA, was used to initiate the polymerization of acrylonitrile (AN) by heating substrates at 85 °C. ¹H and ¹³C NMR and SEC analyses of the products indicated that the triblock copolymer PLA-PAN-PLA formed and thus confirmed the assumed mechanism of the initiation of AN polymerization, which relied on the addition of the radical that formed from TPE (linked with the PLA chain) to the monomer molecule. Copolymerizations were performed with the application of prepared TPE-diET_PLA with three different M_n’s (1400, 2200, and 3300) and with different AN/PLA ratios, producing copolymers with varied compositions, i.e., with AN/LA ratios in the range of 2.3–11.1 and M_n’s in the range of 5100–9400. It was shown that the AN/LA ratio in the copolymer was increasable by the applied excess of AN with respect to the PLA macroiniferter in the feed and that more AN monomer was able to be introduced to PLA with shorter chains.