###### Abstract  
Three four-arm amphiphilic block copolymers with different chain lengths, consisting of a hydrophilic chain of polyethylene glycol (PEG) and hydrophobic segment of polycaprolactone (PCL), were synthesized and used to encapsulate the high-efficient and hydrophobic oxygen probe of platinum(II)-5,10,15,20-tetrakis-(2,3,4,5,6-pentafluorophenyl)-porphyrin (PtTFPP) to form polymer micelles. This approach enabled the use of PtTFPP in aqueous solution for biosensing. Experimental results demonstrated that the particle sizes of these nano-oxygen sensors between 40.0 and 203.8 nm depend on the structures of block copolymers. PtTFPP in these micelles showed an effective quantum yield under nitrogen environment, ranging from 0.06 to 0.159. The new sensors are suitable for analyzing dissolved oxygen concentrations in the range of 0.04-39.3 mg/L by using the linear Stern-Volmer equation at room temperature. In addition, it has been shown that these sensors are capable of in situ monitoring the dissolved oxygens in the culture medium of _E. coli_ and Romas cells during the respiration process, and distinguishing the drug activity of antibiotic ampicillin from that of antimycin A. This study showed that the use of these nanostructured multi-arm block copolymer micelles can achieve efficient biological applications without specific structural modification of the hydrophobic PtTFPP probe, which is expected to have broad prospects. multi-arm block copolymers; oxygen sensors; micelles; oxygen consumption; drug screening 1  
Y. [PERSON], Y.  
and metastatic behavior [17; 18]. Therefore, the ability to measure the oxygen content of tissues and living cells plays a critical role in understanding cellular activities, the pathological causes of disease, and cancer diagnosis. On the other hand, a known fact is that cellular respiration refers to the process in which an organic substance undergoes a series of oxidative decomposition in a cell to produce an inorganic substance or a small molecule organic substance, which releases energy and generates adenosine triphosphate (ATP). Therefore, the measurement of cellular oxygen consumption is of great significance for the evaluation of aerobic glycolysis rate, oxidative phosphorylation, and high-throughput drug screening [19; 20]. The methods currently used to determine oxygen content are limited. The Clark electrode method is the most common method for measuring the partial pressure of oxygen. It is based on current analysis and consists of a platinum electrode wrapped with an oxygen permeable membrane. By applying a voltage, the surface of the electrode undergoes a redox reaction, causing oxygen to be reduced at the surface of the electrode, thereby obtaining an oxygen concentration. However, the Clark electrode method may lead to oxygen consumption and tissue damage. The second common method is also an electrochemical method, and is widely used for measuring oxygen concentration in fuel cells and the automotive industry. However, it is difficult to apply in the biological field. In addition, there are radioisotope methods and magnetic resonance methods, but these techniques are complicated to operate and costly. Therefore, optical sensing and imaging based on luminescence quenching is considered to be a true alternative to the above method, and is replacing the Clark electrode method in many areas [12]. Although there are numerous optical oxygen probes on the market, including some newly synthesized oxygen probes, most of them are hydrophobic [21; 22]. Although hydrophobic probes have high quantum yield, they are difficult to be used in biology. Some hydrophobic probes can be modified directly into hydrophilic oxygen probes; however, the quantum yields of such probes are quite low. For example, the quantum yield of a hydrophilic oxygen probe made of metalloporphyrin (PtCPK, PtCP, PdCPK, PtTCPP) [23; 24] is as low as 0.001-0.0095. Therefore, [PERSON] et al.