【作者】 王焕磊；

【导师】 章东； 郭霞生；

【作者基本信息】 南京大学 ， 声学， 2017， 博士

【摘要】 广泛应用于临床的人体留置装置,如气管插管、导尿管、胃部插管、假肢装置等,在长期驻留体内的过程中,其表面会产生结构复杂的菌膜。菌膜为细菌抵抗外部恶劣环境(如抗生素)提供了屏障,成为医疗感染的主要因素之一。目前临床上对于菌膜抑制的研究大多基于药学和生化原理,如使用抗菌塑料或在留置插管装置表面增加药物涂层(银纳米颗粒、抗生素、水凝胶等),这些方法在一定程度上抑制了菌膜的形成;但对于留置体内时间较长(达几十天)的气管插管,药物涂层效果的持久性面临很大的挑战,一旦菌膜形成,药效将明显降低。超声导波具有沿管状表面长距离传播的特性,以其作为一种表面菌膜抑制的新技术具有较好的发展前景。现阶段,超声导波抑制菌膜形成的相关声学机理研究仍然不够深入,例如导波传播模式、超声振幅、频率等与菌膜抑制效果之间的关系。因此,对插管表面的声波传播模式进行深入地分析和研究,评估不同的超声参数对菌膜抑制的作用,对于新型置入性导管的开发有重要意义。论文从两方面探讨超声对于细菌抑制作用的声学机理及应用:(1)以临床广泛使用的气管插管作为研究对象,研究超声导波的激发频率和幅度对于菌膜抑制效果的影响。首先介绍了超声导波的传播理论,明确了插管上导波存在多种传播模式,并以此为基础确定了导波激发的频率选择依据;实验测量了气管插管的表面振动,分析了插管上导波衰减大的原因;通过耦合剂的结合、导波入射角度的改变等优化实验装置,以提高气管插管表面振动幅度,实验发现可将气管插管的衰减降低15-20dB,气管插管表面能够获得大于5nm的振动。进一步,搭建了一套铜绿假单胞菌菌膜抑制的实验装置,研究了不同振动幅度的导波对气管插管表面菌膜形成过程的抑制效果。结果表明,应用导波后的气管插管表面菌膜形成时间明显延长;在0.5nm-5nm的振动幅度范围内,振动幅度与菌膜抑制效果正相关。(2)从超声促进抗菌药物释放的角度出发,研究超声增强药物的渗透。本文选取两种类抗菌药物进行局部药物传递实验,一是纳米荧光微球(与银纳米抗菌药物在尺度上具有可比性),二是医用透明质酸(HA),其具有长链状结构,分子量较大,可以模拟真实环境下的细菌及药物的粘连。通过共聚焦显微镜和紫外分光测量,实验研究了不同的超声频率(20kHz、200kHz、643.5kHz、1MHz),不同超声强度(25kPa、50kPa、75kPa、100kPa),不同作用时间(5-60分钟)下的药物渗透深度和渗透量。结果发现,超声可促进药物渗透,包括透入深度和浓度。较低的超声频率能得到较好的透药效果,但药物的透入深度很难超过200um。进一步采用微泡(超声造影剂)提高空化作用,发现使用643.5kHz的超声频率透药效果最好,透入深度能达到500um以上,荧光粒子的渗透量提高了 3-5倍,HA的渗透量提高了 7-8倍。论文一方面进行了超声导波抑菌的研究,明确了其声学机制是基于导波传播带来的机械振动,并分析了原型装置的传播模式、频率、振幅等与抑菌效果的关系。另一方面,研究了超声促进药物渗透,特别是引入微泡的空化效应可进一步促进药物渗透。本论文的研究结果揭示了超声对于菌膜抑制和促进抗菌药物渗透方面的有效性,为临床抗菌提供了新的物理方法,有利于新型医用器械的开发。更多还原

【Abstract】 Indwelling devices are widely used in clinical treatments,such as entrocheal tubes,catheter tubes,gastric intubation,prosthetic devices and other surgical implants,etc.Unfortunately,bacteria will attach to the surface and grow as a biofilm,which are protected from being killed by antibiotics.It is increasingly recognized as a key factor in the persistence of varied infections.Many efforts have been made to develop chemical and mechanical approaches for biofilm prevention.Catheters coated with specified antimicrobial materials,including hydrogel,silver salts,silver nanoparticles and antimicrobials,etc.,have been proven effective.Nevertheless,biofilms could still emerge,especially on catheters that remain inside bodies for relatively long periods,e.g.,urinary catheters and endotracheal tubes.Ultrasonic guided wave(UGW)has the characteristics of propagation along the surface of the tube,and it has shown promising for biofilm prevention.Up to now,it is required to deeply understand the acoustic mechanism of biofilm prevention,i.e.,relations of propagation mode,amplitude and frequencyof UGW to the effect of biofilm prevention,which is crucial for the development of implantable catheter.In this thesis,we discussed the acoustic mechanism and the applicationof ultrasound on preventing bacteria and biofilm from two following aspects:(1)The widely used Endotracheal tubes(ETs)wereused as research objects,and the effectof driving parameters of UGW(i.e.frequency and amplitude)on the capability of biofilm prevention was investigated.Firstly,we introduced the theory of UGW propagation,and found that there exist several propagation modeson ETs.We optimized the driving frequency based on the calculation of UGW propagation modes.Secondly,we measured the vibration on the surfaces of ETs,and found the significant attenuations.Consequently,we optimized the experimental setup via various strategies,including the use of the coupling agent and the change of incident angle.After being optimized,the measured amplitude of the acoustic vibrationcould be improved by 15-20 dB(>5 nm).Finally,the optimized setup was used to prevent P.aeruginosa biofilm formation.The prevention of biofilm formation was discussed with respect to varied vibration amplitudes.The experimental results demonstrated that the effects of biofilm prevention wasproportional to the vibration amplitude within the range of 50 pm to 5 nm,which suggestedthe effectiveness of the UGW on biofilms prevention.(2)Ultrasound wasexperimentally used to enhance the deliverypenetration for twosimulated antibacterial drugs.One was fluorescent nanoparticles,which has the similar size of nano sliver,commonly used antibacterial drugs coated on the surface of catheter tube;Another was medical hyaluronic acid(HA)with long chain structure and large molecular weight;it could simulate the adhesion of bacteria and drugs in the real environment.In the present work,ultrasound-facilitated topical drug delivery(TDD)was studied under various acoustic parameters,including frequency(20kHz,200kHz,643.5kHz,1MHz),amplitude(25kPa,50kPa,75kPa,100kPa),and exposure time(5mins to 60mins).The results measuredby laser confocal microscopyand ultraviolet spectrometry showed that ultrasound exposures could improve the permeability,includingthe penetration depth and the delivery concentration.Furthermore,the lower driving frequency could benefit the efficiency of drug delivery,but the penetration depth was less likely to exceed 200 μm for all used frequencies.Moreover,we introduced microbubbles to improve the ultrasound-induced microbubble cavitation effect.The results showed that both the penetration depth and concentration weresignificantly enhanced.The best ultrasound-facilitated TDD could be achieved with a drug penetration depth of over 500 μm,and the penetration concentrations of fluorescent nanoparticles and HAwereincreased up to about 3-5 folds,and 7-8 folds,respectively.In this thesis,the effect of biofilms prevention using the UGW was studied firstly,and the resultsshowed that the acoustic mechanism is based on the mechanical vibration induced by guided wave propagation.Meanwhile,the relationship between the prevention effect with the parameters(propagation mode,frequency and amplitude)was studied.Secondly,ultrasound-facilitated TDD was studied,and better drug penetration depth and concentration were obtained by microbubble enhanced cavitation effect.This work provided new physical methods for clinical antibacterial,which was helpful for the development of new medical devices.更多还原