• <tr id="yyy80"></tr>
  • <sup id="yyy80"></sup>
  • <tfoot id="yyy80"><noscript id="yyy80"></noscript></tfoot>
  • 99热精品在线国产_美女午夜性视频免费_国产精品国产高清国产av_av欧美777_自拍偷自拍亚洲精品老妇_亚洲熟女精品中文字幕_www日本黄色视频网_国产精品野战在线观看 ?

    Surface Modification of Electrospun Poly(L-lactide)/Poly(?-caprolactone) Fibrous Membranes by Plasma Treatment and Gelatin Immobilization

    2021-09-07 02:52:28SHITongna史同娜SHIZhenjiang施鎮(zhèn)江ZHUBingjie朱冰潔WUWenhua吳文華
    關(guān)鍵詞:文華鎮(zhèn)江

    SHI Tongna(史同娜), SHI Zhenjiang(施鎮(zhèn)江), ZHU Bingjie(朱冰潔), WU Wenhua(吳文華)

    National Demonstration Center for Experimental Materials Science and Engineering Education, Donghua University, Shanghai 201620, China

    Abstract: Biopolymer fibers have great potential for technical applications in biomaterials. The surface properties of fibers are of importance in these applications. In this study, electrospun poly(L-lactide) (PLLA)/poly(?-caprolactone) (PCL) membranes were modified by cold plasma treatment and coating gelatin to improve the surface hydrophilic properties. The morphologies of the fibers were observed by scanning electron microscopy (SEM). Atomic force microscopy (AFM) was employed to show the surface characteristics of the fibers. The chemical feature of the fibrous membrane surfaces was examined by X-ray photoelectron spectroscopy (XPS). The surface wettability of the fibrous membrane was also characterized by water contact angle measurements. All these results show that plasma treatment can have profound effects on the surface properties of fibrous membranes by changing their surface physical and chemical features. Gelatin-PLLA/PCL membrane has great potential in applications of tissue engineering scaffolds.

    Key words: surface property; modification; electrospun fiber; plasma treatment; chemical feature; morphology; wettability

    Introduction

    Tissue engineering is rapidly growing into an increasingly important field in regenerative medicine. One of the significant challenges for tissue engineering is to design and fabricate suitable biodegradable scaffolds that are suitable for cell adhesion, growth, proliferation and differentiation, and can guide process of tissue formation[1-2]. Polymer-based nanofibers are considered as a potential material applied in filtration, tissue engineering, and fuel cell[3]. Electrospinning is a well-established process for fabrication of polymeric nanofibers used in scaffolds with high surface areas, large volume-to-mass ratios, and high porosities[4-6]. Recently, polylactone-type biodegradable polymers, such as poly(L-lactide) (PLLA), poly(?-caprolactone) (PCL) and their copolymer poly(L-lactide-co-?-caprolactone) (PLLACL), have been extensively studied as scaffold materials[7-11], since polylactone-type biodegradable polymers possess good mechanical properties, non-toxicity, and adjustable degradation rates. However, the poor hydrophilicity of the polymers affects cells to attach and grow on them when the polymers are used as scaffold materials.

    Plasma treatment is a very promising and frequently used technique for the chemical and physical modification to increase hydrophilicity, which is suitable for most of the materials, especially polymers and polymer fibers[12-13]. Typical plasma treatments with oxygen, ammonia or air can generate carboxyl groups or amine groups on the surface[14-16]. In addition, a variety of extracellular matrix (ECM) protein components, such as gelatin, collagen, laminin and fibronectin, have been immobilized onto the plasma-treated surface to enhance cellular adhesion and proliferation[17-18]. Gelatin is a mixture of proteins which is obtained by hydrolysis of collagen, and it is widely used in tissue engineering due to its biocompatibility, biodegradability and easy availability[19-22]. Gelatin is nonimmunogenic compared with its precursor and can promote cell adhesion, migration, differentiation and proliferation[23-24].

    In this study, the PLLA/PCL (mass ratio was 70∶30) membrane was prepared by electrospinning. However, being synthetic biomaterials, PLLA/PCL membrane is not a good substrate for cell adhesion because of the hydrophobic surface and lacking of functional groups. Thus, Helium (He) plasma treatment was used to modify the electrospun PLLA/PCL membrane, and gelatin was coated onto the He-plasma-treated PLLA/PCL membrane. The fibrous membranes before and after modification were characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS) and water contact angle measurements.

    1 Experiments

    1.1 Materials preparation

    PLLA (Mn=150 000) and PCL (Mn=50 000) were obtained from Sigma-Aldrich Company, Shanghai, China. The polymer solution concentration of 3% (mass percentage) was prepared by dissolving the polymers (the mass ratio of PLLA to PCL was 70∶30) in chloroform. The solution was spun from a 10 mL syringe with a needle of 0.7 mm in diameter. Upon applying a high voltage (10 kV), a fluid jet was ejected from the capillary. As the jet accelerated towards a grounded collector, the solvent evaporated and sub-micron fibers were deposited on an aluminium foil. The distance between the needle and the grounded collector was 20 cm. The PLLA/PCL membrane was dried in a vacuum oven at 37 ℃ for 24 h to remove the residual solvent.

    1.2 Surface modification

    Plasmas were excited with a capacitively coupled 13.56 MHz radio frequency generator capable of delivering a continuously varying power output from 0 to 500 W. The base pressure of the plasma chamber was down to 0 Pa, and the He gas was fed to the chamber until the pressure reached the working pressure of 20 Pa. The electrospun PLLA/PCL fibers were treated at 45 W with He plasma for 2 min. The plasma treated sample was further exposed to the air for 10 min before coating gelatin.

    Anchorage of gelatin was performed by immersing the He-plasma-treated PLLA/PCL sample in 10% (mass percentage) gelatin solution for 12 h at 37 ℃. Then the gelatin-PLLA/PCL sample was washed by distilled water for three times and dried overnight in a vacuum oven. And then it was stored in a desiccator for 12 h at 37 ℃.

    1.3 Morphology observation by SEM

    The original and surface-modified fibrous membranes were characterized by a JSM-5600LV SEM (JEOL, Japan). Prior to SEM examination, a conductive thin gold film was deposited on the specimen surface.

    1.4 Surface structure tested by AFM

    All AFM images were obtained in ambient atmosphere at room temperature with a Nanoscope Ⅳ(Veeco, USA) microscope. The scanning was carried out in contact mode AFM. Each fiber sample was mounted to double-sided tape on magnetic AFM sample stubs.

    1.5 Elemental analysis by XPS

    Changes of the chemical bond environment of the treated samples were examined using the ESCALAB 200R XPS system (V.G Scientific Co., U.K.). Al Kα line (300 W) was used as a source of excitation. The XPS measurements used an Al Kα X-ray source with an optimum energy resolution 0.47 eV. The pressure in the analysis chamber was maintained at 5×10-6Pa.

    1.6 Water contact angle measurement

    The contact angle between water droplets and the surface was measured using a contact anglemeter (Dataphysics Co., Germany) at room temperature. The water droplets made of 3 μL distilled water were dropped at six different spots on each sample, and the average value was adopted.

    2 Results and Discussion

    2.1 Surface morphologies of original and modified PLLA/PCL membranes

    Surface morphology of various PLLA/PCL membranes was observed by SEM technique as shown in Fig. 1. In Figs. 1(a) - (b), it can be seen that the fiber surfaces of original PLLA/PCL film are smooth. However, He-plasma-treated sample presents the formation of groove-like structures on the fiber surfaces as exhibited in Figs. 1(c) - (d). The surface roughness of the fibers is greatly increased by He plasma treatment compared with the surface roughness of untreated ones. This can be attributed to the etching effect of the He plasma treatment. As shown in Figs. 1(e)-(f), distribution of gelatin is much even on the surface of fibers after the PLLA/PCL film is pretreated by He plasma, and the gelatin exhibits as mesh-like structures because of the rough surface of the He-plasma-treated film and subsequent gelatin anchoring process.

    Fig.1 SEM observation of surface morphology of various fibrous membranes: (a) original PLLA/PCL membrane (×1 000); (b) original PLLA/PCL membrane (×5 000); (c) He-plasma-treated PLLA/PCL membrane (×1 000); (d) He-plasma-treated PLLA/PCL membrane (×5 000); (e) gelatin-PLLA/PCL membrane (×1 000); (f) gelatin-PLLA/PCL membrane (×5 000)

    2.2 Surface roughness of original and modified PLLA/PCL fibers

    Topographical examination by AFM indicates the changes in the surface morphology of electrospun PLLA/PCL fibers before and after modification, as shown in Fig. 2. The AFM image in Fig. 2(a) illustrates that the original fiber with diameter ranging from 500 nm to 1 000 nm has relative smooth surface. The image also reveals that the diameter is uneven along an individual fiber. The sample treated by He plasma at 45 W for 2 min in Fig. 2(b) presents nanosize pores and aggregates on the fiber surface, and also there are some protruding particles like dots on the surface. In Fig. 2(c), gelatin distributing on the surface of He-plasma-treated sample results in the formation of groove-like structures on the fiber surface. All these AFM results show the changes on the surface roughness in detail and are consistent with the SEM analysis in Fig. 1.

    Fig. 2 AFM images of original and modified PLLA/PCL fibers:(a) original PLLA/PCL fiber; (b) He-plasma-treated PLLA/PCL fiber; (c) gelatin-PLLA/PCL fiber

    2.3 Surface composition of untreated and treated PLLA/PCL fibrous membranes

    To confirm changes of surface compositions and introduction of additional functional groups, XPS analysis was carried out. XPS is the leading analytical technique for characterizing various chemical/physical forms of elements in surface structures. XPS is especially attractive since additional chemical information can be derived from the line positions of the corresponding peaks[25-26]. Figure 3 shows survey scan spectra and C1s spectra of pristine PLLA/PCL membrane, He-plasma-treated PLLA/PCL membrane and gelatin-PLLA/PCL membrane.

    As can be seen from Fig. 3(a), all XPS spectra have two separated peaks which correspond to C1s (about 285 eV) and O1s (about 532 eV). A distinct N1s peak at 420 eV in the He-plasma-treated PLLA/PCL membrane indicated that a very small amount of nitrogen was introduced on the surface after the plasma-treated sample exposing to air. And the N1s peak in the gelatin-PLLA/PCL membrane spectrum indicated that gelatin had been successfully introduced onto the fiber surface. In addition, all the peaks on the spectra moved to lower-binding energy from curve A to curve C in Fig. 3(a).

    Fig.3 XPS survey scan spectra and C1s spectra of various PLLA/PCL membranes: (a) full spectra; (b) C1s spectra

    Table 1 Surface composition of various samples measured by XPS

    2.4 Water contact angle analysis for untreated and treated PLLA/PCL membranes

    The effect of plasma treatment and coating gelatin on the hydrophilicity of the PLLA/PCL membrane was shown in Fig. 4. As seen in Fig. 4, the water contact angle of the original PLLA/PCL membrane is found to be about 133°. After He plasma treatment, it appears that the water contact angles of the surface decease from 130° to 0° in 40 s. This can be attributed to the polar groups of the fibers and the rough surfaces. It is evident that He plasma treatment considerably reduces the water contact angle on the membrane surface. He plasma treatment is an effective method to introduce oxygen containing groups (such as carboxyl and hydroxyl groups) onto polymer surfaces. This simple method was used in this work to improve the hydrophilicity and introduce carboxyl groups onto the PLLA/PCL membrane surface for the possibility of gelatin grafting in aqueous solution. After gelatin was attached to the He-plasma-treated surface, the water contact angles dropped rapidly from 105° to 0° in 12 s, which further indicated the carboxyl groups generated on the plasma-treated surface conjugated with gelatin.

    Fig. 4 Water contact angles of (a) original PLLA/PCL membrane; (b) He-plasma-treated PLLA/PCL membrane; (c) gelatin-PLLA/PCL membrane

    3 Conclusions

    This study has explored the effects of plasma treatment and gelatin coated on PLLA/PCL membranes. It has shown that plasma treatment can have profound effects on the surface properties of fibrous membrane by changing their surface physical and chemical features. Furthermore, gelatin was successfully anchored on the surface of electrospun PLLA/PCL membrane by He plasma treatment, as evident from a detailed physical and chemical characterization of gelatin-PLLA/PCL membrane. And the surface hydrophilicity of modified fibrous membrane has been greatly improved. The modification of electrospun fibers surface by plasma pretreatment and bound gelatin has great potential in applications such as biomaterials, sensors and medical devices, which is expected to carry out cell culture research in the next step.

    猜你喜歡
    文華鎮(zhèn)江
    移火柴棒
    鎮(zhèn)江大地 詩意棲居
    華人時刊(2021年13期)2021-11-27 09:19:22
    賽珍珠:我在鎮(zhèn)江有個家
    華人時刊(2020年17期)2020-12-14 08:13:00
    我的鎮(zhèn)江尋根之旅
    華人時刊(2020年17期)2020-12-14 08:12:54
    填 數(shù)
    陳文華
    寶藏(2018年6期)2018-07-10 02:26:36
    倪文華 作品
    鎮(zhèn)江學(xué)前教育體制改革的實踐探索
    鎮(zhèn)江是這樣調(diào)價的
    A?。裕颍椋幔睿纾欤濉。拢欤铮悖耄ㄒ粋€三角木塊)
    www.熟女人妻精品国产| 好看av亚洲va欧美ⅴa在| 性欧美人与动物交配| 亚洲精品美女久久久久99蜜臀| 国产精品综合久久久久久久免费 | 久热这里只有精品99| 久久精品国产亚洲av香蕉五月| 国产男靠女视频免费网站| 咕卡用的链子| 高清在线国产一区| 熟妇人妻久久中文字幕3abv| 国产亚洲精品综合一区在线观看 | 久久草成人影院| 大型av网站在线播放| 国产91精品成人一区二区三区| 老司机靠b影院| 国产欧美日韩一区二区三区在线| 国产日韩一区二区三区精品不卡| 给我免费播放毛片高清在线观看| 免费在线观看黄色视频的| tocl精华| 色av中文字幕| 午夜久久久在线观看| 久久国产精品人妻蜜桃| 黑人欧美特级aaaaaa片| 熟妇人妻久久中文字幕3abv| 少妇粗大呻吟视频| 99re在线观看精品视频| 欧美av亚洲av综合av国产av| 老司机在亚洲福利影院| 高清在线国产一区| 女人爽到高潮嗷嗷叫在线视频| 黄色毛片三级朝国网站| 老司机福利观看| 久久久久久久久免费视频了| 精品国产一区二区久久| 50天的宝宝边吃奶边哭怎么回事| 国产高清videossex| 一级,二级,三级黄色视频| 国产xxxxx性猛交| 女人高潮潮喷娇喘18禁视频| 欧美日韩亚洲国产一区二区在线观看| 看黄色毛片网站| svipshipincom国产片| 正在播放国产对白刺激| 亚洲天堂国产精品一区在线| 国产极品粉嫩免费观看在线| 国产片内射在线| 50天的宝宝边吃奶边哭怎么回事| 中文字幕高清在线视频| 日本一区二区免费在线视频| 国产极品粉嫩免费观看在线| 最新美女视频免费是黄的| 欧美色视频一区免费| 给我免费播放毛片高清在线观看| 色尼玛亚洲综合影院| 亚洲国产日韩欧美精品在线观看 | 三级毛片av免费| 久久香蕉国产精品| 亚洲中文字幕一区二区三区有码在线看 | 在线观看舔阴道视频| 精品久久久久久久人妻蜜臀av | 色综合亚洲欧美另类图片| 久久国产精品男人的天堂亚洲| 黄色成人免费大全| 99久久国产精品久久久| cao死你这个sao货| 变态另类丝袜制服| 少妇 在线观看| 午夜福利影视在线免费观看| 国产成人欧美| 男人舔女人下体高潮全视频| 精品国产乱码久久久久久男人| 宅男免费午夜| 美女高潮喷水抽搐中文字幕| 亚洲五月天丁香| 欧美激情极品国产一区二区三区| 国产在线观看jvid| 黄色视频,在线免费观看| 精品人妻1区二区| 咕卡用的链子| 夜夜躁狠狠躁天天躁| 中文字幕久久专区| 在线观看免费视频网站a站| 男女下面进入的视频免费午夜 | 亚洲自拍偷在线| 日韩欧美三级三区| 国产亚洲精品久久久久5区| 一区二区三区精品91| 丝袜人妻中文字幕| 欧美另类亚洲清纯唯美| 久久影院123| 国产成人啪精品午夜网站| 国产亚洲精品一区二区www| 在线国产一区二区在线| 亚洲国产欧美日韩在线播放| 国产高清激情床上av| 岛国视频午夜一区免费看| 亚洲精品粉嫩美女一区| 99香蕉大伊视频| 制服人妻中文乱码| 亚洲av五月六月丁香网| av欧美777| 丝袜美腿诱惑在线| 国产区一区二久久| 国产成人免费无遮挡视频| 美女扒开内裤让男人捅视频| 一卡2卡三卡四卡精品乱码亚洲| 亚洲精品国产色婷婷电影| 精品久久久久久久人妻蜜臀av | 久久精品成人免费网站| 嫁个100分男人电影在线观看| 久久草成人影院| 怎么达到女性高潮| 天天一区二区日本电影三级 | 久久久久九九精品影院| 国产精品 欧美亚洲| 看免费av毛片| 欧美一级a爱片免费观看看 | 欧美日韩亚洲综合一区二区三区_| 在线永久观看黄色视频| 一个人观看的视频www高清免费观看 | 亚洲专区中文字幕在线| 欧美久久黑人一区二区| 怎么达到女性高潮| 亚洲专区字幕在线| 18禁观看日本| 久久精品国产亚洲av香蕉五月| 久久人妻熟女aⅴ| 好男人在线观看高清免费视频 | 视频在线观看一区二区三区| 中文字幕人妻熟女乱码| 国产aⅴ精品一区二区三区波| 午夜福利影视在线免费观看| 亚洲自拍偷在线| 国产一区二区三区在线臀色熟女| 国产亚洲av嫩草精品影院| 午夜福利成人在线免费观看| 久久九九热精品免费| 亚洲情色 制服丝袜| 老熟妇仑乱视频hdxx| 国产成人精品在线电影| 丰满人妻熟妇乱又伦精品不卡| 黑人巨大精品欧美一区二区mp4| 色综合亚洲欧美另类图片| 亚洲五月婷婷丁香| 久久久久久久久中文| 午夜福利18| 满18在线观看网站| 啦啦啦观看免费观看视频高清 | 国产麻豆69| 欧美日韩瑟瑟在线播放| 国产精品综合久久久久久久免费 | 久久久久国产一级毛片高清牌| 黑人操中国人逼视频| 国产精品久久久久久亚洲av鲁大| 午夜亚洲福利在线播放| 在线播放国产精品三级| 妹子高潮喷水视频| 免费在线观看完整版高清| 一本久久中文字幕| 一级毛片精品| 美女大奶头视频| 满18在线观看网站| 久久午夜综合久久蜜桃| 精品一区二区三区视频在线观看免费| 久久久久久久午夜电影| 夜夜夜夜夜久久久久| 久久影院123| 久久亚洲精品不卡| 日韩高清综合在线| 色尼玛亚洲综合影院| 日韩中文字幕欧美一区二区| 免费av毛片视频| 久久精品成人免费网站| 欧美另类亚洲清纯唯美| 久久久久国产精品人妻aⅴ院| 日本欧美视频一区| 亚洲一码二码三码区别大吗| 正在播放国产对白刺激| 每晚都被弄得嗷嗷叫到高潮| 国产精品av久久久久免费| 最新在线观看一区二区三区| 亚洲av成人一区二区三| 亚洲欧美日韩无卡精品| 最近最新中文字幕大全免费视频| 成人亚洲精品av一区二区| 天天一区二区日本电影三级 | 电影成人av| 色尼玛亚洲综合影院| 久久香蕉精品热| 天堂√8在线中文| 一级作爱视频免费观看| netflix在线观看网站| 午夜精品国产一区二区电影| 久久人妻熟女aⅴ| 精品久久久久久成人av| 午夜激情av网站| 国产欧美日韩一区二区三| 制服丝袜大香蕉在线| 成年女人毛片免费观看观看9| 国产精品乱码一区二三区的特点 | 亚洲成人精品中文字幕电影| 国产成人精品久久二区二区91| √禁漫天堂资源中文www| 午夜福利影视在线免费观看| 少妇被粗大的猛进出69影院| 久久午夜亚洲精品久久| 国内精品久久久久精免费| 一级a爱视频在线免费观看| 婷婷六月久久综合丁香| 别揉我奶头~嗯~啊~动态视频| 国产精品亚洲美女久久久| 精品国产美女av久久久久小说| 国产野战对白在线观看| 黄色视频,在线免费观看| 亚洲天堂国产精品一区在线| 欧美在线黄色| 人人妻人人澡人人看| 激情在线观看视频在线高清| 亚洲人成77777在线视频| 国产成人啪精品午夜网站| 天天躁夜夜躁狠狠躁躁| 国产色视频综合| 中文字幕精品免费在线观看视频| 国产成年人精品一区二区| 亚洲第一欧美日韩一区二区三区| 男人舔女人的私密视频| 欧美乱妇无乱码| 亚洲最大成人中文| 90打野战视频偷拍视频| 精品一区二区三区av网在线观看| 久久久国产欧美日韩av| 一进一出抽搐动态| 色哟哟哟哟哟哟| 国产成人精品久久二区二区91| 亚洲精品av麻豆狂野| 久热这里只有精品99| 国产麻豆69| 久久香蕉精品热| 免费观看人在逋| 我的亚洲天堂| 国产蜜桃级精品一区二区三区| 热99re8久久精品国产| 一二三四在线观看免费中文在| 90打野战视频偷拍视频| 欧美最黄视频在线播放免费| 国产主播在线观看一区二区| 国产麻豆69| 亚洲国产高清在线一区二区三 | 欧美日韩乱码在线| 亚洲色图综合在线观看| 在线免费观看的www视频| 欧美一级毛片孕妇| 亚洲精品在线美女| 国产精品久久久久久人妻精品电影| 国产精品一区二区免费欧美| 久热这里只有精品99| 99久久精品国产亚洲精品| 亚洲 欧美 日韩 在线 免费| 色精品久久人妻99蜜桃| 色婷婷久久久亚洲欧美| videosex国产| 免费观看精品视频网站| 宅男免费午夜| 亚洲精品国产色婷婷电影| 在线视频色国产色| 国内精品久久久久久久电影| 少妇粗大呻吟视频| 国产av又大| 亚洲专区国产一区二区| 母亲3免费完整高清在线观看| 国产亚洲精品综合一区在线观看 | 国产真人三级小视频在线观看| 国产成人av教育| 在线观看www视频免费| 日日干狠狠操夜夜爽| 丁香六月欧美| 亚洲激情在线av| 欧美一级毛片孕妇| 国产在线观看jvid| 国产成人欧美在线观看| 女人高潮潮喷娇喘18禁视频| 亚洲人成伊人成综合网2020| 国产精品综合久久久久久久免费 | 亚洲va日本ⅴa欧美va伊人久久| www.999成人在线观看| svipshipincom国产片| 精品久久久久久,| av福利片在线| 午夜视频精品福利| 久久久久国内视频| 精品不卡国产一区二区三区| 亚洲国产精品成人综合色| 韩国av一区二区三区四区| 欧美日本中文国产一区发布| 啦啦啦观看免费观看视频高清 | 久久国产亚洲av麻豆专区| 免费在线观看完整版高清| 法律面前人人平等表现在哪些方面| 女人高潮潮喷娇喘18禁视频| 国产精品美女特级片免费视频播放器 | 国产精品精品国产色婷婷| 脱女人内裤的视频| 欧美老熟妇乱子伦牲交| 久久草成人影院| 久久久久亚洲av毛片大全| 午夜免费激情av| 777久久人妻少妇嫩草av网站| 日韩视频一区二区在线观看| 国产av一区在线观看免费| 美女大奶头视频| 97超级碰碰碰精品色视频在线观看| 国产高清视频在线播放一区| 精品欧美国产一区二区三| 亚洲欧美日韩另类电影网站| 老鸭窝网址在线观看| 在线十欧美十亚洲十日本专区| 亚洲狠狠婷婷综合久久图片| 中文字幕高清在线视频| 91成年电影在线观看| 啦啦啦观看免费观看视频高清 | 色播在线永久视频| 欧美日韩中文字幕国产精品一区二区三区 | av免费在线观看网站| а√天堂www在线а√下载| 亚洲av成人一区二区三| 国产精品自产拍在线观看55亚洲| 脱女人内裤的视频| 国产精品九九99| 淫妇啪啪啪对白视频| 一进一出好大好爽视频| 最近最新中文字幕大全电影3 | 黄色视频不卡| 久久 成人 亚洲| 久久精品影院6| 人人澡人人妻人| 1024香蕉在线观看| 欧美大码av| 他把我摸到了高潮在线观看| 午夜久久久久精精品| 日本 av在线| 校园春色视频在线观看| 亚洲片人在线观看| 亚洲精品国产一区二区精华液| 美女大奶头视频| 亚洲成国产人片在线观看| 涩涩av久久男人的天堂| 两人在一起打扑克的视频| 久久久久亚洲av毛片大全| 99久久国产精品久久久| 国产av在哪里看| 欧美色欧美亚洲另类二区 | 午夜成年电影在线免费观看| 国产精品久久久人人做人人爽| 午夜久久久在线观看| 美女大奶头视频| 可以免费在线观看a视频的电影网站| av中文乱码字幕在线| 国产麻豆69| 亚洲av成人不卡在线观看播放网| 两人在一起打扑克的视频| 99国产极品粉嫩在线观看| 青草久久国产| 欧美亚洲日本最大视频资源| av福利片在线| 国产精品影院久久| 久久久国产成人精品二区| 人人妻人人澡欧美一区二区 | 婷婷六月久久综合丁香| av天堂久久9| av视频免费观看在线观看| 午夜久久久在线观看| 久久精品aⅴ一区二区三区四区| 日韩欧美在线二视频| 亚洲欧美日韩无卡精品| 熟女少妇亚洲综合色aaa.| 男女下面进入的视频免费午夜 | 99精品在免费线老司机午夜| 90打野战视频偷拍视频| 午夜福利影视在线免费观看| 大型av网站在线播放| 手机成人av网站| 国产成人精品久久二区二区91| www日本在线高清视频| 日日干狠狠操夜夜爽| 成人国产综合亚洲| 母亲3免费完整高清在线观看| 国产精品一区二区精品视频观看| 十八禁人妻一区二区| 国产精品亚洲一级av第二区| 久久性视频一级片| 亚洲国产欧美日韩在线播放| 久久久精品国产亚洲av高清涩受| 久久人人精品亚洲av| 性欧美人与动物交配| 日本欧美视频一区| 伦理电影免费视频| 国产欧美日韩精品亚洲av| 啦啦啦观看免费观看视频高清 | 熟妇人妻久久中文字幕3abv| 国产精品久久久久久人妻精品电影| 国产精品98久久久久久宅男小说| 国产亚洲av嫩草精品影院| 老汉色∧v一级毛片| 精品熟女少妇八av免费久了| 婷婷精品国产亚洲av在线| 十分钟在线观看高清视频www| 午夜福利18| 成人三级做爰电影| 宅男免费午夜| 免费在线观看日本一区| 99精品欧美一区二区三区四区| 两个人看的免费小视频| 国产精品日韩av在线免费观看 | 99国产精品一区二区蜜桃av| 亚洲人成网站在线播放欧美日韩| 后天国语完整版免费观看| 午夜视频精品福利| 99久久精品国产亚洲精品| 天天躁狠狠躁夜夜躁狠狠躁| 亚洲av电影不卡..在线观看| 一进一出好大好爽视频| xxx96com| 美女高潮到喷水免费观看| 波多野结衣巨乳人妻| 久久人妻福利社区极品人妻图片| 曰老女人黄片| 桃红色精品国产亚洲av| 好男人电影高清在线观看| 性少妇av在线| avwww免费| 在线播放国产精品三级| 久久久水蜜桃国产精品网| 日韩 欧美 亚洲 中文字幕| 美女扒开内裤让男人捅视频| 美女高潮喷水抽搐中文字幕| 丝袜美足系列| 亚洲精品中文字幕一二三四区| 亚洲最大成人中文| 嫁个100分男人电影在线观看| 黄色 视频免费看| 很黄的视频免费| 波多野结衣av一区二区av| 午夜福利成人在线免费观看| 亚洲av美国av| 真人做人爱边吃奶动态| а√天堂www在线а√下载| 黄色成人免费大全| 别揉我奶头~嗯~啊~动态视频| 日本五十路高清| 欧美一级毛片孕妇| 在线免费观看的www视频| 国产成人免费无遮挡视频| 中文字幕另类日韩欧美亚洲嫩草| 国产乱人伦免费视频| 两性夫妻黄色片| 日韩欧美国产一区二区入口| 欧美另类亚洲清纯唯美| 91精品三级在线观看| 精品久久久久久久人妻蜜臀av | 成人精品一区二区免费| 两个人视频免费观看高清| 久久香蕉精品热| 国产精品美女特级片免费视频播放器 | 波多野结衣一区麻豆| 91字幕亚洲| 久久久久久亚洲精品国产蜜桃av| 久久亚洲精品不卡| 99精品在免费线老司机午夜| 搡老妇女老女人老熟妇| 亚洲国产高清在线一区二区三 | 亚洲男人的天堂狠狠| 人人妻人人爽人人添夜夜欢视频| 9191精品国产免费久久| cao死你这个sao货| 久久婷婷成人综合色麻豆| e午夜精品久久久久久久| 国产又色又爽无遮挡免费看| 夜夜躁狠狠躁天天躁| 大陆偷拍与自拍| 老熟妇乱子伦视频在线观看| 亚洲五月婷婷丁香| 亚洲少妇的诱惑av| 亚洲精品国产色婷婷电影| 国产三级黄色录像| 国产精品国产高清国产av| 久久精品成人免费网站| 韩国精品一区二区三区| 欧美中文综合在线视频| 深夜精品福利| 久久精品亚洲精品国产色婷小说| 这个男人来自地球电影免费观看| 大型黄色视频在线免费观看| 亚洲精品国产一区二区精华液| 天堂动漫精品| 免费在线观看视频国产中文字幕亚洲| 一边摸一边抽搐一进一小说| 老司机在亚洲福利影院| 99在线视频只有这里精品首页| 涩涩av久久男人的天堂| 天堂影院成人在线观看| 亚洲无线在线观看| av免费在线观看网站| 久99久视频精品免费| 国产三级在线视频| 成人18禁高潮啪啪吃奶动态图| 淫秽高清视频在线观看| 久热爱精品视频在线9| 一进一出抽搐动态| 亚洲精品久久成人aⅴ小说| 99精品在免费线老司机午夜| av视频在线观看入口| 999精品在线视频| 少妇的丰满在线观看| 亚洲第一青青草原| 亚洲国产日韩欧美精品在线观看 | 最近最新中文字幕大全电影3 | 麻豆av在线久日| 黄色 视频免费看| 亚洲成a人片在线一区二区| 午夜福利一区二区在线看| 窝窝影院91人妻| 51午夜福利影视在线观看| 亚洲国产高清在线一区二区三 | 日韩欧美国产在线观看| 成在线人永久免费视频| 午夜两性在线视频| 两人在一起打扑克的视频| 1024香蕉在线观看| 午夜福利影视在线免费观看| 成人手机av| 亚洲国产精品999在线| 久久久久久久久免费视频了| 黄频高清免费视频| 免费在线观看影片大全网站| 国产亚洲欧美精品永久| 19禁男女啪啪无遮挡网站| 女性被躁到高潮视频| 高清毛片免费观看视频网站| 久久久国产欧美日韩av| 淫妇啪啪啪对白视频| 男女之事视频高清在线观看| 丝袜在线中文字幕| 精品久久久久久成人av| videosex国产| 欧美成人午夜精品| 久久久国产成人精品二区| 中文字幕人妻丝袜一区二区| 亚洲自偷自拍图片 自拍| 亚洲色图 男人天堂 中文字幕| 美女免费视频网站| 高潮久久久久久久久久久不卡| 国产高清有码在线观看视频 | 一级毛片精品| 亚洲黑人精品在线| 波多野结衣高清无吗| 国产人伦9x9x在线观看| 国产精品自产拍在线观看55亚洲| 黄网站色视频无遮挡免费观看| 十分钟在线观看高清视频www| 欧美黑人欧美精品刺激| 欧美 亚洲 国产 日韩一| 国产熟女午夜一区二区三区| 国产一区在线观看成人免费| 久久 成人 亚洲| 午夜福利在线观看吧| 男女午夜视频在线观看| 久久人妻av系列| 久久人妻福利社区极品人妻图片| 亚洲精品中文字幕在线视频| 亚洲avbb在线观看| 国产精品爽爽va在线观看网站 | 黑人巨大精品欧美一区二区蜜桃| 日韩欧美国产在线观看| 免费女性裸体啪啪无遮挡网站| 国产99白浆流出| 亚洲avbb在线观看| 午夜福利免费观看在线| 日韩中文字幕欧美一区二区| 大码成人一级视频| 国产黄a三级三级三级人| 亚洲欧美精品综合一区二区三区| 在线观看日韩欧美| 午夜福利一区二区在线看| 精品久久久精品久久久| 精品欧美国产一区二区三| 在线观看免费视频网站a站| 色播在线永久视频| 两性夫妻黄色片| 日韩精品免费视频一区二区三区| 亚洲av片天天在线观看| 一本久久中文字幕| 中文字幕人成人乱码亚洲影| 丝袜美足系列| 两性夫妻黄色片| 在线观看免费视频网站a站| 国产亚洲精品av在线| 青草久久国产| 日本 av在线| 好看av亚洲va欧美ⅴa在| 国产熟女午夜一区二区三区| 国产真人三级小视频在线观看| 中文字幕高清在线视频| 禁无遮挡网站| 国产xxxxx性猛交| 亚洲av成人一区二区三| 亚洲色图 男人天堂 中文字幕| 日本 av在线| 亚洲一区二区三区不卡视频| 中文字幕人妻熟女乱码| 1024香蕉在线观看| 久久久久国产精品人妻aⅴ院| 国内精品久久久久久久电影| 免费高清视频大片|