外文翻譯----殼聚糖聚乙烯醇復(fù)合水凝膠的制備

1、<p>　　附件 </p><p>　　畢業(yè)論文(設(shè)計(jì))外文資料翻譯</p><p>　　附件1：外文資料翻譯譯文</p><p>　　殼聚糖-聚乙烯醇復(fù)合水凝膠溶脹度及其生物相容性</p><p>　　2.2.1殼聚糖溶液和PVA溶液制備</p><p>　　首先，聚乙烯醇水凝膠的制備，是先稱

2、5.0g聚乙烯醇粉末使其在100ml純凈水中進(jìn)一步完全溶解，同時(shí)在電磁攪拌下，溫度控制75±2℃（溶液A），就像我們團(tuán)隊(duì)之前的報(bào)道所示。[7-9]。5％的聚乙烯醇完全溶解后，讓其冷卻到室溫和用1.0 M鹽酸（）把pH值控制在（2.00±0.05）。殼聚糖水凝膠（殼聚糖）制備采用相似的步驟，稱2.5g殼聚糖在250ml 2％的醋酸溶液（）中，電磁攪拌48小時(shí)（溶液B）。</p><p>　　2.

3、2.2殼聚糖和聚乙烯醇復(fù)合水凝膠制備</p><p>　　用不同量的聚乙烯醇溶液（溶液A）加入到1.0％的殼聚糖溶液（溶液B）獲得以下幾種殼聚糖/聚乙烯醇水凝膠，分別質(zhì)量比為（0:1），（1:3 ），（1:1），（3:1）和（1:0）和用1.0M氫氧化鈉溶液把pH值調(diào)節(jié)在（4.00±0.05）。將該混合物繼續(xù)攪拌5分鐘，直到聚乙烯醇和殼聚糖完全形成了清澈溶液。然后，緩慢加入交聯(lián)劑（戊二醛），并不斷攪拌。

4、在溶液凝膠初期，戊二醛的最后濃度為1％和5％（質(zhì)量分?jǐn)?shù)％）。隨著進(jìn)一步反應(yīng)，溶液不斷塑化，接著在室溫下其讓干燥72至120 h，最后在40℃干燥24小時(shí)（恒重）。殼聚糖-聚乙烯醇復(fù)合水凝膠樣品的化學(xué)交聯(lián)反應(yīng)產(chǎn)生凹痕已確定為（X： Y： Z）三種因素，X為殼聚糖的含量，Y為聚乙烯醇的含量，Z為戊二醛（質(zhì)量分?jǐn)?shù)%）。例如，樣品組成確定為殼聚糖/聚乙烯醇/戊二醛=（1:3:1）,則：25％的殼聚糖，75％聚乙烯醇和1.0％（質(zhì)量分?jǐn)?shù)％）戊二醛

5、。干凝膠儲(chǔ)存在干燥器之前，要記錄樣品每一個(gè)特征。</p><p>　　2.3.4.1 溶脹度測試</p><p>　　流體吸收研究是初步分析生物降解材料至關(guān)重要的步驟。測定流體攝取量，所有殼聚糖-聚乙烯醇水凝膠的樣品摩爾比為0:1，1:3，1:1，3:1和1:0時(shí)，制備如前一節(jié)所描述的，都是質(zhì)量比（W%），然后在37℃下，浸泡于吸附液體中。經(jīng)過不同時(shí)間長度的浸泡后，用濾紙把表面上的水去掉，

6、小心的將樣品放到適當(dāng)?shù)娜萜髦?，然后測定樣品的濕重（g），分析與浸泡時(shí)間的關(guān)系[9]。計(jì)算如下面的公式：</p><p>　　每個(gè)樣品溶脹度實(shí)驗(yàn)重復(fù)做三次，取平均值。</p><p>　　3.4.1 溶脹度測試</p><p>　　溶脹度的實(shí)驗(yàn)主要研究殼聚糖/聚乙烯醇水凝膠合成時(shí)，不同混合比例和戊二醛交聯(lián)劑用量對溶脹度的影響。典型的溶脹行為如圖4所示：殼聚糖/聚乙烯

7、醇配比（25：75），交聯(lián)劑用量為1%和5%。簡單地說，從觀察表明，最初30分鐘出現(xiàn)迅速大規(guī)模吸收，其次變?yōu)榫徍?，超過192小時(shí)后，基本穩(wěn)定不變?？瓷先悠敷w積有明顯的膨脹。結(jié)果表明，強(qiáng)交聯(lián)度越大，膨脹體積也越大，膨脹最大達(dá)到殼聚糖-聚乙烯水凝膠交聯(lián)之前體積的7倍，當(dāng)交聯(lián)劑用量分別為1.0％和5.0％時(shí)膨脹度下降到400％和200％。這現(xiàn)象是由于高分子鏈在反應(yīng)時(shí)形成交錯(cuò)的網(wǎng)絡(luò)空間結(jié)構(gòu)，減少了分子活動(dòng)性和水凝膠內(nèi)一些不利于膨脹率的親水基團(tuán)

8、。因此，這些結(jié)果相當(dāng)于說明水凝膠溶脹的行為原因。在戊二醛加入反應(yīng)之前，聚乙烯醇分子鏈結(jié)合到殼聚糖分子鏈段上，形成了水凝膠網(wǎng)絡(luò)結(jié)構(gòu)。接著，當(dāng)戊二醛加入，發(fā)生化學(xué)交聯(lián)反應(yīng)，在鏈段間形成共價(jià)鍵，固定聚合物和降低流動(dòng)性，引起較少的溶脹率，也許，只有一半不到的混合物發(fā)生交聯(lián)反應(yīng)。</p><p>　　改變殼聚糖在聚乙烯醇中的配比，分析影響如圖5所示。實(shí)驗(yàn)表明，殼聚糖的含量對水凝膠溶脹行為的影響尤為明顯，固定交聯(lián)劑在5.0％

9、時(shí)，水凝膠溶脹度隨殼聚糖濃度的增加而減少，殼聚糖/聚乙烯醇= 50:50時(shí)，達(dá)到最低值。</p><p>　　這些結(jié)果能支持理解交聯(lián)反應(yīng)如何發(fā)生在復(fù)合水凝膠內(nèi)，戊二醛與殼聚糖的胺基反應(yīng)，比與聚乙烯醇的羥基反應(yīng)多很多。最小值出現(xiàn)在50：50處（圖5）可能是胺基與羥基數(shù)目相等有關(guān)，從而形成較硬的殼聚糖/聚乙烯醇鏈，令兩者流動(dòng)性迅速下降。盡管目前的研究不同于其他殼聚糖的研究報(bào)道，但聚乙烯醇和殼聚糖的溶脹行為與這些結(jié)論相

10、似，聚乙烯醇的溶脹度在500%以上，殼聚糖大約是200%，取決于溶液中的PH值，溫度等等。</p><p><b>　　4 結(jié)論</b></p><p>　　在目前的研究中，殼聚糖-聚乙烯醇混合物都是由人工用化學(xué)交聯(lián)得到的雙功能醛。結(jié)果表明，通過改變殼聚糖與聚乙烯醇中的比例，不同的交聯(lián)劑濃度，水凝膠的整體性能是可以改變的。這次的實(shí)驗(yàn)報(bào)告已指出溶脹性能與殼聚糖含量的增加

11、，還有交聯(lián)試劑用量的增大有很大的關(guān)系。這現(xiàn)象產(chǎn)生的原因是形成了一個(gè)十分緊密的網(wǎng)絡(luò)結(jié)構(gòu)。此外，細(xì)胞相容性實(shí)驗(yàn)已經(jīng)證明，所有實(shí)驗(yàn)結(jié)果評價(jià)是無毒，無排斥性和生物相容性好?？傊@些研究擴(kuò)大了殼聚糖/聚乙烯醇混合物等一些生物材料在醫(yī)學(xué)領(lǐng)域的應(yīng)用的潛力，如生物材料，毒品運(yùn)載工具和皮膚組織工程。</p><p>　　附件2：外文原文（復(fù)印件）</p><p>　　Properties and bioc

12、ompatibility of chitosan ?lms modi?ed by blending with PVA and chemically crosslinked</p><p>　　2.2.1 Chitosan and PVA solution preparation</p><p>　　Brie?y, PVA hydrogels were prepared by fully d

13、issolving 5.0g of polymer powder without further puri?cation in 100 ml of Milli-Q water, under magnetic stirring, at temperature of 75 ± 2℃ (solution A), as previously reported by our group [7–9]. PVA 5% solution wa

14、s let to cool down to room temperature and the pH was corrected to (2.00 ± 0.05) with 1.0 M HCl (Sigma). Chitosan hydrogels (Chi) were produced in a similar procedure by fully dissolving 2.5g in 250.0ml of Milli-Q w

15、ater with 2% of CH3COOH </p><p>　　2.2.2 Chitosan, PVA and blends ?lms preparation</p><p>　　Different quantities of PVA (solution A) were added into the 1.0% chitosan solution (solution B) to obt

16、ain chitosan/PVA mass ratios of (0:1), (1:3), (1:1), (3:1), and (1:0) and pH was corrected to (4.00 ± 0.05) with 1.0 M NaOH solution. The mixture was kept under stirring for 5 min until the PVA and chitosan complete

17、ly formed a clear solution. Then, the crosslinker reagent (GA) was slowly added under constant stirring. The ?nal concentration of GA in the gel solution precursors was 1% and 5% (wt</p><p>　　2.3.4.1 Swellin

18、g test </p><p>　　Fluid absorption studies are of paramount importance for preliminary analysis of biode-gradable materials. For ?uid-uptake measurements, all the specimens of the chitosan/PVA hydrogels with

19、molarratios of 0:1, 1:3, 1:1, 3:1, and 1:0 were prepared as described in the previous section, were weighed (W0) before being immersed in SBF at 37℃. After immersion for different time periods, the samples were carefully

20、 removed from the medium and, after wiping off water excess on the surface with ?lter pape</p><p>　　Each SBF absorption experiment was repeated three times and the average value was taken to validate theresu

21、lts.</p><p>　　3.4.1 Swelling test </p><p>　　Swelling experiments were conducted with Chi/PVA blends, with different polymer proportions and crosslinkedby GA. A typical swelling behavior is show

22、n in Fig.4 performed for Chi/PVA blend [25:75] before and after chemical crosslinking with 1% and 5% of content. Brie?y, the observed pattern indicated an initial rapid mass uptake,usually in approximately 30 min, follow

23、ed by mass stabilization over a 192 h period. Visual inspection of the samples also shows appreciable volume increase. The results </p><p>　　That fact is attributed to a more rigid network formed by the inte

24、r-intra polymer chain reactions that have occurred, reducing the ?exibility and number of hydrophilic groups of hydrogel which is unfavorable to the swelling rate. So, these results are cor-responding to the hydrogel mec

25、hanism. Before GA reaction, the PVA chains are physically entangled with the chitosan chains, forming a hydrogel network. In the sequence, when the GA content was increased the chemical crosslinking has occurred, f</p

26、><p>　　The effect of chitosan to PVA ratio was also analyzed and the results are presented in Fig. 5. It was veri?ed that the swelling behavior is especially in?uenced by the chitosan content in the blend, cros

27、slinked at 5.0%GA,where the swollen mass reduced by increasing the chitosan concentration and reaching a minimum value at [Chi/PVA] =50:50. The swelling degree reduced from 200%(pure PVA) to 100% (50:50 Chi/PVA), then ra

28、ised to about140% at Chi/PVA ratios of 75:25 and 100% chitosan.</p><p>　　These results are supported by understanding the cross-linking reaction which has occurred in the blended hydrogels, where the amine g

29、roups of chitosan are more reactive to GA than hydroxyls of PVA. The minimum value observed at 50:50 (Fig.5) is probably related to the overall balance between amine and hydroxyl crosslinking which is caused by the forma

30、tion of a rigid structure amongst the Chi/PVA chains, reducing drastically their possibility of solution uptake. Despite of the present research b</p><p>　　4 Conclusion</p><p>　　In the present r

31、esearch, chitosan/PVA blends were synthesized and chemically crosslinked with bi-functional aldehyde. The results have shown that by altering the proportion of chitosan to PVA, associated with different crosslinker conce

32、ntration, the overall properties from hydrogels can be modi?ed. The systems investigated have indicated a signi?cant reduction on the swelling behavior as the chitosan content was increased and also as the amount of cros