MEMS-based surface acoustic wave technology in microbiology: bioaerosol atomization, encapsulation and storage = Yi wei dian ji xi tong wei ji chu de biao mian sheng bo ji shu yu wei sheng wu xue de yan jiu : sheng wu qi rong jiao de wu hua, bao guo ji chu cun

M.Phil.Bioaerosols consist of fine airborne particles, including bacteria, fungi, endotoxin and other substances of a biogenic origin. Bioaerosol is a rising concern worldwide posing significant implications to human health. Quantification and characterization of bioaerosols in a chemical and biological sense is of utmost importance. Bioaerosol sampling remains a challenging bottleneck because of the loss of microbial viability and desiccation stress during conventionally used processes, such as inertial impaction, direct impingement, electrostatic precipitation, and sedimentation. Efficient and high-throughput bioaerosol sampling, monitoring and archiving are imperative to the epidemiological investigation of infectious diseases, understanding of the spread and control of airborne microorganisms, monitoring of biohazards and establishing air quality standards.In this thesis, I have developed a surface acoustic wave (SAW) atomization technology to transport airborne aerosols to a polydimethylsiloxane (PDMS) booklet for the non-destructive individual assessment, transportation and long term storage. Bacillus atrophaeus and Bacillus subtilis endospores were collected by impinging on a thin layer of molten low-gelling-point agarose. SAW was propagated at 19.825 MHz frequencies with a power of 2 W along the surface of a 127.86º y-x cut lithium niobate piezoelectric crystal substrate by applying a high-frequency electromagnetic signal to the interdigitated gold and chromium microelectrodes. Atomization of the colloid gave rise to monodisperse aerosol microspheres, with encapsulated bioaerosols, upon rapid cooling and solidification in the air. The microbead size distribution followed a lognormal distribution with a peak diameter at 4 μm. Aerosolization of microspheres formed a spray of mist to adhere to a PDMS matrix. Another transparent gas-permeable polymer film was covered so that bioaerosol microspheres could readily be transported, detected, incubated and stored in the form of a booklet. Individual encapsulated endospores could readily be observed under microscopy. Micro-colonies could quickly be detected by conventional microscopic observation or optical density measurement. Endospores subjected to atomization followed by over 6 months of storage at 45 ºC produced 16S rRNA gene amplification fragments up to 1604 bp in length. No deleterious effect on DNA was noted. Microscopy and culture studies revealed no observable changes on endospore morphology and culturability.Our results demonstrated that bioaerosols could be sampled and encapsulated in the agarose microbeads by SAW atomization with a controllable size distribution without affecting the viability and DNA content. This methodology enables high-throughput and efficient encapsulation of bioaerosol into solid agarose microspheres for better compartmentalization, spatial indexing, and more quantitative assessment on archival bioaerosol viability. The storage of bioaerosols inside agarose microbeads allowed re-interrogation at any time, in addition to space-efficient room temperature storage of samples and inexpensive sample transport by mail. It is particularly useful in environmental sampling where immediate sample processing or refrigeration is unavailable.生物氣溶膠是由微小懸浮粒子包括細菌、真菌、內毒素以及其他生物性物質所組成，其對人體健康的顯著影響於近年逐漸引起國際間關注。為對生物氣溶膠作深入了解，生物學和化學上的定量及特征分析為重要的方法。然而，現時生物氣溶膠的取樣技術仍然面對相當大的困難。常用的傳統撞擊式、靜電集塵技術及沉澱式取樣器均會對樣本受乾燥應力影響及導致微生物活性下降。為了解空氣中的微生物的傳播及傳染病和流行病學調查，以制定空氣質數的標準和監測生物危害的水平，建立高效率而高吞吐量的生物氣溶膠取樣、監察及存檔的技術是當務之急。在這篇論文中，我已開發出一種以表面聲波霧化技術來傳送空氣中的氣溶膠到聚二甲基矽氧烷所組成的小冊子上作非破壞性的獨立評估，運輸及長期儲存之用。萎縮桿菌及枯草桿菌的內生孢子透過直接撞擊到薄層的低凝膠溫度的瓊脂糖進行收集。表面聲波通過在金/鉻交叉指形微電極上施加高頻電磁信號以19.825兆赫的頻率及2瓦特的功率沿127.86° y-x 切割的鈮酸鋰壓電晶體上傳遞。膠體透過表面聲波霧化產生了單分散的氣溶膠微球體並同時包裹生物氣溶膠，及後在空氣中急速冷卻下凝固。微球體的大小分佈遵循對數常態分佈而其峰值直徑為4微米。微球體的霧化形成噴霧並粘附到聚二甲基矽氧烷的基體之上，並由另一個透明及透氣的聚合物所做成的膜所覆蓋。這種方法使被微球體所包裹的生物氣溶膠可以容易地被運輸、檢測、培養並於小冊子之中的形式儲存。獨立包裹的內生孢子可以很容易地在顯微鏡下進行觀察。微菌落可以快速地通過傳統顯微鏡來觀察或進行光密度檢測。霧化後的內生孢子樣本於攝氏45度下貯存超過六個月後進行長度達1604組鹼基對的16S核餹體核糖核酸基因擴増。當中並無發現任何脫氧核醣核酸的受損或有害的影響，而且透過顯微鏡的檢查及培養研究下均顯示孢子的形態和培養性並無任何明顯的變化。我們的研究結果表明生物氣溶膠可以在不影響生物活性和脫氧核醣核酸的含量下利用表面聲波霧化技術進行取樣並以在可控的大小分佈下包裹於瓊脂糖微球體內。這種方法可以實現以高效率而高吞吐量的模式下把生物氣溶膠包裹於固體的瓊脂糖微球體內以達致對生物氣溶膠採樣樣本的生物活性能夠作更好的分隔、空間索引及定量評估。存儲於瓊脂糖微球體內的生物氣溶膠能容許在任何時間之下進行檢測，而且能夠在室溫下保存並通過郵件把取樣本直接運送以大幅減少儲藏空間的要求及繁複的運送處理程序。此方法用於環境取樣方面，尤其在無法即時直接檢測樣本或無法對樣本進行冷卻的情況中特別有用。Chan, Wai Chun.Thesis M.Phil. Chinese University of Hong Kong 2014.Includes bibliographical references (leaves 53-62).Abstracts also in Chinese.Title from PDF title page (viewed on 13 March, 2018).Chan, Wai Chun.Detailed summary in vernacular field only.Detailed summary in vernacular field only.Detailed summary in vernacular field only