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水凝膠+奈米海綿 美科學家打敗超級細菌

美國加州大學聖地牙哥分校的科學家開發出可對抗致命「超級細菌」的新型水凝膠。

水凝膠的孔大小恰好可以鎖住奈米海綿,但讓毒素進入,和奈米海綿結合。(來源:Weiwei Gao/Jacobs School of Engineering/UC San Diego)

奈米海綿裝入水凝膠 治療細菌感染

水凝膠就是水和聚合物組成的凝膠,而這種新型水凝膠富含可吸收毒素的奈米海綿,能有效治療局部細菌感染。

「奈米海綿難以單獨用於治療,因為在人體組織內會快速四處滲透。將奈米海綿裝進水凝膠中,則可將奈米海綿留在感染部位。」研究作者、加州大學聖地牙哥分校奈米工程教授張良方說。

研究者說,由於奈米海綿水凝膠不含抗生素,效果不受細菌抗藥性的影響,也不會發展出新的抗藥性。

不只是住院病患 超級細菌擴及全世界2%人口

根據WebMD網站的資訊,超級細菌──抗生素耐藥性金黃色葡萄球菌(MRSA,methicillin-resistant Staphylococcus aureus)於1961年被發現,現在已經可以耐受甲氧西林、阿莫西林、青黴素、苯唑西林,和許多其他常用的抗生素。

MRSA透過接觸傳染,接觸帶菌者的皮膚或沾有細菌的物體可造成傳染。

約有2%的人口帶有MRSA。MRSA感染常發生於免疫系統脆弱者、醫院、護理之家和其他健康照護中心,感染部位可能是手術傷口、導管或植入餵食管周邊。

根據美國疾病管制預防中心的資料,醫院的侵入性MRSA感染發生率在2011年至2013年間減少了8%。但令衛生官員擔憂的是,MRSA開始出現在沒住過院的健康人體,如運動員、入伍新兵、囚犯和托兒所兒童。

有些抗生素仍然有用,但MRSA持續在適應中,讓開發新抗生素的研究人員疲於奔命。

完美結合 水凝膠和奈米海綿效果佳

張良方解釋,每個奈米海綿就像是外面包了一層紅血球細胞膜的奈米粒子。紅血球是MRSA毒素的真正目標,而這一層膜讓奈米海綿假裝成紅血球,吸收MRSA毒素,將毒素從血管中清除。

為了讓奈米海綿移除特定部位的毒素,如感染的皮膚傷口,必須將大量奈米海綿留在定點,水凝膠就發揮這樣的作用,將每毫升數十億的奈米海綿留在感染處。

水凝膠的孔大小恰好可以鎖住奈米海綿,但讓毒素進入,和奈米海綿結合。「注射奈米海綿水凝膠於患部後,可觀察到奈米海綿水凝膠吸收細菌分泌的毒素,避免進一步傷害局部血液、肌膚和肌肉組織。」張良方說。

研究人員發現,奈米海綿水凝膠可以防止MRSA感染的皮膚傷口擴大。在小鼠身上,用奈米海綿水凝膠治療的傷口比未治療者小。

研究團隊也發現,水凝膠可以固定奈米海綿在人體內的位置。將奈米海綿水凝膠注射於小鼠皮下,兩天後仍有80%的奈米海綿在原處。而若單獨注射奈米海綿,兩小時後只有20%留在原處,大多數滲透近周邊組織。

Nanosponges in Disguise Mop Up MRSA Staph Infections
SAN DIEGO, California, May 19, 2015 (ENS)

A new gel filled with nanosponges that absorb toxins has proven effective against the “super bug” MRSA (methicillin-resistant Staphylococcus aureus), an antibiotic-resistant bacteria that can be life-threatening.

Nanoengineers at the University of California, San Diego developed the new hydrogel – a gel made of water and polymers – packed with the toxin-absorbing nanosponges.

“Nanosponges alone are difficult to use on local tissues because they diffuse away to other parts of the body very quickly,” explained Liangfang Zhang, nanoengineering professor in the Jacobs School of Engineering at UC San Diego, who led the team, “By integrating the nanosponges into a hydrogel, we can retain them at the site of infection.”

Since the nanosponge-hydrogel treatment does not involve antibiotics, the researchers say that it will not likely be affected by existing bacterial antibiotic resistance.

Also, because antibiotics are not involved, the nanosponge-hydrogel treatment will likely not cause bacteria to develop new resistance.

MRSA was first discovered in 1961. It’s now resistant to methicillin, amoxicillin, penicillin, oxacillin, and many other common antibiotics, according to the website WebMD.

MRSA is spread by contact – touching the skin of a person who has the bacteria or by touching objects that have the bacteria on them.

MRSA is carried by about two percent of the population. MRSA infections are common among people who have weak immune systems and are in hospitals, nursing homes, and other health care facilities. Infections can appear around surgical wounds or medical devices, such as catheters or implanted feeding tubes.

According to the Centers for Disease Control and Prevention, invasive MRSA infections that began in hospitals declined eight percent between 2011 and 2013.

But health officials are alarmed because MRSA is also showing up in healthy people who have not been hospitalized, such as team athletes, military recruits, prison inmates and children in daycare.

While some antibiotics still work, the MRSA bacteria is constantly adapting. Researchers developing new antibiotics are having a tough time keeping up.

Zhang explains how the new treatment works. Each nanosponge is a nanoparticle coated in a red blood cell membrane. This coating disguises the nanosponges as red blood cells, which are the real targets of the harmful toxins produced by MRSA.

By masquerading as red blood cells, the nanosponges attract harmful toxins and remove them from the bloodstream.

In order for the nanosponges to remove toxins from a specific spot, such as an infected skin wound, a lot of them need to be held at that spot.

This is where the hydrogel plays a role; it can hold billions of nanosponges per milliliter in one place.

The hydrogel’s pores are small enough to keep most of the nanosponges from escaping and large enough so that toxins can easily get inside and attach to the nanosponges.

The researchers showed that the nanosponge-hydrogel treatment kept down the size of skin lesions caused by MRSA infections.

In mice, the skin lesions that were treated with the nanosponge-hydrogel were smaller than those that were left untreated.

“After injecting the nanosponge-hydrogel at the infected spot, we observed that it absorbed the toxins secreted by the bacteria and prevented further damage to the local blood, skin and muscle tissues,” said Zhang.

The team also showed that the hydrogel was effective at holding the nanosponges in place within the body. Two days after the nanosponge-hydrogel was injected beneath the skin of a mouse, nearly 80 percent of the nanosponges were still at the injection site.

When nanosponges were injected without the hydrogel, only 20 percent of them remained at the injection site after two hours. Most of them diffused to the surrounding tissues.

※ 全文及圖片詳見:ENS

- See more at: http://e-info.org.tw/node/107582#sthash.WYFAXRnZ.dpuf

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