(Front) Mr Lin Sheng, (back, from left) Dr Edmond Ma and Miss Ko Chung-nga invent a luminescent complex that can rapidly and sensitively detect lead ions in water using only a portable device.


A schematic diagram of the luminescent switch-on assay that monitors the presence of lead ions using a G-quadruplex-selective probe.

圖中顯示新檢測方法的原理:複合物(圖中Complex 1)作為探針,因檢測到鉛離子引起的DNA結構改變而增強發光。

Date: 27 Oct 2015 (Tuesday)


HKBU scientist invents metal complex to rapidly detect lead contamination in water


Dr Edmond Ma, Associate Professor of the Department of Chemistry of HKBU, and his collaborators have invented a luminescent metal complex which rapidly detects lead ions in water. This new DNA-based method requires less than 10 minutes to sensitively detect lead contamination using only a portable instrument and a laptop. This cost-effective method attains results with greater accuracy and sensitivity. The team has filed a provisional patent for this invention in the US.

The project entitled “A luminescent iridium(III) complex and its uses thereof for the G-quadruplex-based switch-on rapid detection of lead ions” is the result of a collaboration between Dr Edmond Ma, Dr Duncan Leung Chung-Hang, Associate Professor, Institute of Chinese Medical Sciences of the University of Macau, HKBU PhD student Mr Lin Sheng and Miss Ko Chung-nga (Chemistry, Year 4).

The team developed the synthesis and use of a luminescent iridium(III) complex for the construction of a label-free G-quadruplex-based assay for the rapid detection of lead ions in aqueous solution. Dr Ma said, “The presence of lead ions is known to induce a structural change in DNA from single-stranded to a special conformation called a G-quadruplex. This change in structure is recognised by the luminescent iridium(III) complex with an enhanced emission response, allowing the system to function as a luminescent “switch-on” probe for lead ions. Therefore, we could use this assay to determine whether the water sample contains excessive lead ions.”

Their experiments showed that as the concentration of lead ions increased, the system experienced a gradual increase in luminescence intensity. This indicates that this G-quadruplex-based sensing platform is a potential method to rapidly detect lead ions in tap water, offering a promising tool for environmental and water safety monitoring.

Dr Ma also explained that conventional methods for detection of lead in water tend to take a longer time (more than 15 minutes), require steps involving expensive pre-labeling (with an intermediate agent such as fluorophore), and may produce false positive results owing to influence by other compounds in real water samples. In contrast, the method developed by their team shows good selectivity towards lead ions and has the ability to detect lead ions in drinking water at concentrations as low as 10 ppb (the World Health Organization safety standard). Due to the versatility of DNA and the iridium(III) complex, the team’s next step is to develop paper testing strip based on the same mechanism, which could allow the general public to conveniently test the presence of lead ions in drinking water at home, with ease of use  comparable to that of a pH test paper or pregnancy test kit.

The rapid detection method of lead ions developed by the team is shown in the following video (in Chinese):

The study was supported by the HKBU Century Club.





馬博士補充說,傳統測試食水含鉛量的方法一般需時較長(超過15分鐘)、需要昂貴的檢測標示劑(如熒光劑),更可能因水樣本中其他雜質的影響而出現誤導的檢測結果。相反,以新方法檢測鉛含量的靈敏度高,更可檢測食水中低至10 ppb的鉛含量(濃度單位ppb為十億分之一,10 ppb是世界衛生組織所規定的安全標準)。此外,DNA和銥(III)複合物的結構靈活多變,團隊期望根據相同的檢測原理研製出快速檢測紙條,方便度可媲美酸鹼試紙或驗孕試劑,讓一般市民在家也可檢測食水是否含鉛。