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ÓиßÊÖ°ïÎÒ·ÁË µ«ÊÇÎÒ¾õµÃ²»ÊǺܺà ϣÍûÓиü¸ßµÄÊÖ°ïÎÒ¿´Ò»Ï ллÀ² £¨ÒÔÏÂÊÇÓ¢ÎĺÍÖÐÎÄ£© 2. Materials and methods 2.1. Materials The chitosan used in this study to prepare the CS¨CMMTnanohydrogels was supplied by Aldrich¨CSigma and usedwithout purification. The same type of chitosan was usedby Darder et al., who reported that it has an averagemolecular weight of 342,500 g mol1 and a deacetylationdegree (DD) of ca. 75% [14]. Acetic acid and sodium phosphatefor the preparation of buffers were purchased fromAldrich Chemicals. Vitamin B12 (Sigma¨CAldrich Co.) waschosen as a model molecule to characterize the releasebehavior from the nanohydrogel. Na+-montmorillonite,supplied by Nanocor Co., is an Na+ form of layered smectiteclay with a cationic exchange capacity (CEC) of120 meq. (100 g)1. The MMT platelet shows a surfacedimension of about 200¨C500 nm in length and several tensof nanometers in width.2.2. Preparation of CS¨CMMT nanohydrogelsTo prepare the CS¨CMMT nanohydrogels, the preparationprocedure is separated into two stages. The first stageis to prepare a suspension containing MMT and CS with aweight ratio of 1:2 (where the CS solution was prepared bydissolving predetermined amounts of CS in 1 wt.% aceticacid solution and stirring for about 4 h until the CS wascompletely dissolved). The CS¨CMMT suspensions wereobtained by adding CS to an aqueous solution containing2 wt.% MMT (i.e. 0.5 g of Na+-MMT dispersed in 25 mlof double-distilled water), followed by stirring at 50 Cfor 24 h. To enhance the formation of exfoliation of theMMT in the final nanohydrogel, the suspension with aCS to MMT ratio of 2:1 was then subjected to ball-millingfor 24 h, after which the as-prepared final CS¨CMMT suspensionwas used to form nanohydrogel.In the second stage of the CS¨CMMT nanohydrogelpreparation, 2 wt.% CS solution was obtained by dissolvingCS in 1 wt.% acetic acid solution. A small amount ofthe ball-milled CS¨CMMT suspension was then added tothe prepared CS solution to form a CS-rich suspension,with the MMT content controlled in the range of 1, 2, 3and 4 wt.%, relative to the total weight of CS in the suspensions,under continuous stirring at 60 C for 1 h. This finalsuspension was then cast onto Petri dishes and dried at30 C for 24 h, to form final dried nanohydrogels. Thedried nanohydrogels were then rinsed with an aqueoussolution of 1 M NaOH to remove any residual acetic acid,followed by washing with distilled water and drying for 1week at 40 C in vacuum until use. The compositions ofthe nanohydrogels are expressed using the value of n todefine the content of MMT in CS¨CMMTn, wheren = C mmt, the content of the MMT incorporated in thenanohydrogels, which ranged from 1% to 4%.2¡£ ²ÄÁϺͷ½·¨ 2. 1 ²ÄÁÏ ÔÚÕâÏîÑо¿ÖÐÓÃÀ´±àÖÆCSµÄ¿Ç¾ÛÌÇÃÉÍÑÍÁnanohydrogelsÊÇÎ÷¸ñÂêÌṩ²¢ÇÒʹÓÃûÓо»»¯¡£¿Ç¾ÛÌǵÄͬÀàÐÍÊÇusedby Darder¸ù¾ÝÆä±¨¸æËµ£¬Æ½¾ù·Ö×ÓÁ¿Îª342,500 g mol_1 ºÍÍÑÒÒõ£¶È£¨DD£©Îª75%µÄ¸Æ¡£ 75£¥´×ËáÄÆÁ×ËáÁ×ËỺ³åµÄ×¼±¸¹º×ÔAldrich»¯Ñ§Æ·¡£Î¬ÉúËØB12£¨Sigma¨CAldrichÓÐÏÞ¹«Ë¾£©ÊÇÑ¡Ôñ×÷ΪһÖÖģʽÀ´ÃèÊö·Ö×ÓÊÍ·Å´Ó½ºÌåÊÍ·ÅÐÐΪ¡£ÄÆMMTÓÉNanocor¹«Ë¾ÌṩµÄ£¬ÊÇÄÆÀë×ӵķֲãÒ»½ìµÄÐÎʽµÙÌØÕ³ÍÁµÄÑôÀë×Ó½»»»ÈÝÁ¿£¨CEC£©ÒªÇóµÄ120ºÁ¿Ëµ±Á¿£¨100¿Ë£©Ã¿Éý¡£MMTѪС°å±íÃæÏÔʾԼ200-500΢Ã׳¤£¬¼¸Ê®ÄÉÃ׵Ŀí¶È¡£2. 2 CS -MMTÈܽºµÄÖÆ±¸ CS -MMTÈܽºµÄÖÆ±¸¿ÉÒÔ·ÖΪÁ½¸ö½×¶Î¡£ µÚÒ»½×¶ÎÊÇ×¼±¸º¬ÓÐMMTºÍCSÖØÁ¿1:2µÄ±ÈÀý£¨ÈçCSÈÜÒºÖÆ±¸ÈܽâÔÚ1CSµÄÔ¤¶¨Êý¶î¡£wt£¥´×ËáÈÜÒººÍ½Á°èÔ¼4Сʱ£¬Ö±ÖÁCS³¤ÊÇÍêÈ«Èܽ⣩¡£ÔÚCS -ÃÉÍÑÍÁÐü¸¡»ñµÃ¼ÓÈëCSË®ÈÜÒºÖк¬2΢ÉýÃÉÍÑÍÁ£¨Èç0¡£5ÄÆ¿Ë+ÃÉÍÑÍÁ·ÖÉ¢ÔÚ25ºÁÉýË«ÕôÁóË®£©£¬Æä´ÎÊÇ50½Á°è¾ùÔÈ24Сʱ Ϊ¼ÓÇ¿¶Ô°þÀëµÄÐγÉÃÉÍÑÍÁÔÚ×îºónanohydrogel£¬ÓëCSÍò¶ÖµÄ±ÈÀýΪ2:1µ±Ê±Êܵ½ÇòĥΪ24Сʱ£¬Ö®ºóËùÖÆ±¸µÄ×îÖÕCSÃÉÍÑÍÁÊÇÓÃÀ´ÐγÉnanohydrogel¡£ÔÚµÚ¶þ½×¶ÎµÄCSÃÉÍÑÍÁnanohydrogel×¼±¸2΢Éý¡£CSÈÜÒºµÃµ½Èܽ⣬1 £¥´×ËáÈÜÒº¡£ÉÙÁ¿µÄÔÚÇòÄ¥CSÃÉÍÑÍÁÔÝͣȻºóÌí¼Óµ½CS×¼±¸µÄ½â¾ö·½°¸£¬ÐγÉÒ»¸öCS·á¸»µÄÈÜÒº£¬ÓëÃÉÍÑÍÁº¬Á¿ÔÚ1£¬2£¬3·¶Î§¿ØÖƺÍ4¸ö΢Éý¡£Ïà¶ÔÓÚCSµÄ×ÜÖØÁ¿£¬ÔÚÁ¬Ðø60¡æ½Á°è1 hºóÕâ×îºóÊܵ±Ê±µ½µ½ÅàÑøÃóºÍ30¶È¸ÉÔï24Сʱ£¬ÒÔÐγÉ×îÖյĸÉnanohydrogels¡£ÄǸö¸ÉnanohydrogelsÈ»ºóÓëÇâÑõ»¯ÄÆÈÜÒº³åÏ´£¬ÒÔÏû³ýÈκβÐÁô´×ËᣬÆä´ÎÊÇÓÃÕôÁóˮϴµÓºÍ¸ÉÔï1ÔÚ40ÉãÊ϶ÈʹÓÃÒ»ÖÜ¡£×é³ÉµÄÔÚnanohydrogelsÊDZíʾʹÓÃnµÄ¼ÛÖµÔÚCS¶¨ÒåÃÉÍÑÍÁº¬Á¿MMTn£¬ÆäÖÐñ = CMMT£¬ÔÚÉó²Ã´¦µÄÄÚÈÝÄÉÈënanohydrogels£¬´Ó1£¥ÖÁ4£¥²»µÈ |
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