Design and construction of poly (L-lactic-acid) nanofibrous yarns and threads with controllable structure and performances.

The design and development of electrospun nanofibrous yarns (ENYs) have attracted intensive attentions in the fields of biomedical textiles and tissue engineering, but the inferior fiber arrangement structure, low yarn eveness, and poor tensile properties of currently-obtained ENYs has been troubled for a long time. In this study, a series of innovative strategies which combined a modified electrospinning method with some traditional textile processes like hot stretching, twisting, and plying, were designed and implemented to generate poly (L-lactic-acid) (PLLA) ENYs with adjustable morphology, structure, and tensile properties. PLLA ENYs made from bead-free and uniform PLLA nanofibers were fabricated by our modified electrospinning method, but the as-spun PLLA ENYs exhibited relatively lower fiber alignment degree and tensile properties. A hot stretching technique was explored to process the primary PLLA ENYs to improve the fiber alignment and crystallinity, resulting in a 779.7% increasement for ultimate stress and a 470.4% enhancement for Young's modulus, respectively. Then, the twisting post-treatment was applied to process as-stretched PLLA ENYs, and the tensile performances of as-twisted ENYs was found to present a trend of first increasing and then decreasing with the increasing of twisting degree. Finally, the PLLA threads made from different numbers of as-stretched PLLA ENYs were also manufactured with a traditional plying process, demonstrating the feasibility of further improving the yarn diameter and tensile properties. In all, this study reported a simple and cost-effective technique roadmap which could generate high performance PLLA nanofiber-constructed yarns or threads with controllable structures like highly aligned fiber orientation, twisted structure, and plied structure.

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.

Preparation, function, and safety evaluation of a novel degradable dermal filler, the cross-linked poly-γ-glutamic acid hydrogel particles.

Poly-γ-glutamic acid (PGA) is a naturally degradable hydrophilic linear microbial polymer with moisturizing, immunogenic, cross-linking, and hydrogel water absorption properties similar to hyaluronic acid, a biomaterial that is commonly used as a dermal filler. To explore the development feasibility of cross-linked PGA as a novel dermal filler, we studied the local skin response to PGA fillers and the effect of various cross-linking preparations on the average longevity of dermal injection. Injection site inflammation and the formation of collagen and elastin were also determined. PGA hydrogel particles prepared using 28% PGA and 10% 1,4-butanediol diglycidyl ether showed optimal filler properties, resistance to moist heat sterilization, and an average filling longevity of 94.7 ± 61.6 days in the dermis of rabbit ears. Local redness and swelling due to filler injection recovered within 14.2 ± 3.6 days. Local tissue necrosis or systemic allergic reactions were not observed, and local collagen formation was promoted. Preliminary results suggested that dermal injection of cross-linked PGA particles appeared safe and effective, suggesting that cross-linked PGA particles could be developed as a new hydrogel dermal filler.

Effects of chitosan and heparin on early extension of burns.

Chitosan, a naturally occurring high-molecular glycosaminoglycan (GAG), has been widely used in wound healing, including burns. Heparin is also a highly used glycosaminoglycan in burns. To evaluate the effects of chitosan and heparin alone and the mixture of chitosan and heparin on early extension of burn wound, deep partial-thickness burns were performed on the dorsum of rats. Then chitosan and heparin powder and the mixture of chitosan and heparin were applied, respectively, on the burn wounds. After 72 h, histological examination of the burn wounds was performed. Outcome showed that the burn degree of chitosan group was less severe than control group and chitosan greatly prevented the extension of burns in early phase. However, heparin had no protective effect on the early extension of burns. Use of chitosan and heparin together attenuated chitosan's protective effect.

[Preparation and characterization of chitosan coated puerarin liposomes].

OBJECTIVE: To prepare chitosan coated puerarin liposomes and investigate their physicochemical properties. METHODS: Puerarin liposomes were prepared by reverse phase evaporation technique and then coated with chitosan. Using encapsulation efficiency as index of examination and designing an orthogonal experiment, the optimal formulation of liposomes was determined. The physicochemical properties of uncoatd and chitosan coated puerarin liposomes were investigated, respectively. RESULTS: Uncoated and chitosan coated puerarin liposomes were spherelike and smooth. The mean particles size of uncoated and coated liposomes were 217. 3nm and 632. 6nm, respectively. The Zeta potential were -14.44 mV and +35.61 mV, respectively. The encapsulating efficency was 50. 6% and 51.1%, respectively. CONCLUSION: Puerarin liposomes can be prepared by reverse phase evaporation technique successfully. The chitosan coated purarin liposomes ware spherelike and smooth.

Effects of the bilayer nano-hydroxyapatite/mineralized collagen-guided bone regeneration membrane on site preservation in dogs.

This study was aimed at assessing the effects of the porous mineralized collagen plug with or without the bilayer mineralized collagen-guided bone regeneration membrane on alveolar ridge preservation in dogs. The third premolars in the bilateral maxilla of mongrel dogs ( N = 12) were extracted. Twenty-four alveolar sockets were thus randomly divided into three groups: membrane + collagen plug (MP, n = 8), nonmembrane + collagen plug (NP, n = 8) and blank group without any implantation (BG, n = 8). Radiographic assessment was carried out immediately and in the 2nd, 6th, and 12th week after surgery. The bone-repairing effects of the two grafts were respectively evaluated by clinical observation, X-ray micro-computed tomography examination, and histological analysis in the 8th and 12th week after surgery. Three groups presented excellent osseointegration without any inflammation or dehiscence. X-ray micro-computed tomography and histological assessment indicated that the ratios of new bone formation of MP group were significantly higher than those of NP group and BG group in the 8th and 12th week after surgery ( P < 0.05). As a result, the porous mineralized collagen plug with or without the bilayer mineralized collagen-guided bone regeneration membrane could reduce the absorption of alveolar ridge compared to BG group, and the combined use of porous mineralized collagen plug and bilayer mineralized collagen-guided bone regeneration could further improve the activity of bone regeneration.

Toward immunosuppressive effects on liver transplantation in rat model: tacrolimus loaded poly(ethylene glycol)-poly(D,L-lactide) nanoparticle with longer survival time.

In this study, tacrolimus (FK506) was encapsulated into a biodegradable poly(ethylene glycol)-poly(D,L-lactide) (MPEG-PLA) block copolymer using a double emulsion-solvent evaporation technique. Drug loading (DL) and encapsulation efficiency (EE) can be changed by varying the mass ratio of FK506/MPEG-PLA. Furthermore, transmission electron microscope (TEM) and Malvern Zetasizer were used to investigate the properties of FK506/MPEG-PLA nanoparticles (DL=9.5%), which were monodisperse (PDI=0.100 ± 0.023) with a mean particle size of 90.5 ± 1.5 nm. Compared with FK506 capsule, in vitro release profile showed that FK506/MPEG-PLA nanoparticles exhibited sustained release. Meanwhile, the higher concentration and longer retention time in plasma were also confirmed in vivo. We further preliminarily evaluated immunosuppressive effect on liver transplantation in rat model. The survival time of the rat administrated FK506/MPEG-PLA nanoparticles was obviously prolonged than that of the control group administrated FK506 capsule.

Preparation and evaluation of folate-modified cationic pluronic micelles for poorly soluble anticancer drug.

The aim of this study was to construct novel targeting polymeric micelles. Folate-Poly (ethylenimine)-Pluronic copolymers were synthesized. A paclitaxel (PTX)-loaded mixed micelles consisting of Folate-Poly (ethylenimine)-Pluronic and Pluronic L121 copolymers have been developed. The mixed micelles showed nano-sized spherical morphology. The solubilization capacity of the mixed micelles was higher than Folate-Poly (ethylenimine)-Pluronic micelles because L121 has high solubilization capacity. MTT colorimetric test revealed that PTX in Folate-Poly (ethylenimine)-Pluronic micelles demonstrated the maximum anticancer activity. Pluronic-poly (ethylenimine) micelles and folate-modified Pluronic-poly(ethylenimine) micelles showed a marked increase of cellular accumulation compared with Pluronic P123 micelles. The biodistribution and retention of intravenously (i.v.) administered micelles to rats were determined. Folate-Poly (ethylenimine)-Pluronic micelles demonstrated enhanced pulmonary retention in rats after injection when compared to Pluronic P123 micelles.