I-electrochemistry ye-methylene blue: ama-electrode, izinkomba ze-redox, nezinzwa

Umfundi owenza izifundo ezilandela iziqu zokuqala wenza i-cyclic voltammogram ye-methylene blue ku-electrode yekhabhoni eyingilazi, abone ipheya ecacile yeziqongo, bese ephetha ngokuthi inzwa isiphelile. Ngemva kwesonto, iziqongo sezisukile, zancipha, noma zahlukana, futhi akukho enqubweni echaza ukuthi kungani. Udayi awushintshanga. Ukuqonda okwakusekela isilinganiso kwakungaphelele.

I-methylene blue ibalulekile ku-electrochemistry ngenxa yezizathu ezintathu. Ishintshisana ngama-electron ngendlela ebuyiseleka emuva emandleni kagesi aphansi, inamathela ezindaweni ezingaphezulu futhi yakhe amafilimu ngokuhlangana ibe yi-polymer, futhi ibopha ama-nucleic acid. Ngayinye yalezi iyindlela ehlukile, futhi ngayinye inendlela yayo yokwehluleka. Lokhu kubuyekezwa kuyazihlukanisa: ipheya, ukufundwa kwesignali, i-electrode eguquliwe, indima yokulamula, nezakhiwo zezinzwa ezakhiwe phezu kwalokhu.

Ipheya elilodwa, izinhlobo ezimbili, i-proton eyodwa

Ukusabela okuyisisekelo ku-pH engathathi hlangothi kuvame ukubhalwa njenge-cation eyodwa esesimweni se-oxidation ethatha ama-electron amabili ne-proton eyodwa ukuze ikhiqize uhlobo lwe-leuco olusesimweni se-reduction, olungenambala:

MB+ + H+ + 2e- gives LMB

Amandla kagesi e-redox e-methylene blue ku-pH 7 acishe abe ngu-+11 mV uma eqhathaniswa ne-electrode ejwayelekile ye-hydrogen, njengoba kubikiwe ocwaningweni lwakamuva lwendlela udayi osebenza ngayo ku-Chemistry Europe. Njengoba i-proton eyodwa ihambisana nama-electron amabili, amandla kagesi asemthethweni ashintsha cishe ngo-30 mV aye ohlangothini olunegethivu ngokwenyuka ngakunye kwe-pH ngeyunithi eyodwa. Lelo thambeka liyinkomba yokuqala okufanele uyibambe ngekhanda. Uma isiqongo sakho sihamba cishe ngo-30 mV ngeyunithi ye-pH, ubuka ipheya elilindelekile. Uma sihamba ngo-60 mV ngeyunithi, inani lama-proton selishintshile. Uma singanyakazi cishe nhlobo, isignali ingase ivele kufilimu engaphezulu enamakhemikhali ayo e-asidi ne-base, kunokuba ivele kudayi oncibilikile.

Ukucacisa ama-electrode okuyireferensi kungumkhuba wesibili. Amandla kagesi abikwe ngokuqhathaniswa ne-Ag/AgCl, i-SCE, ne-NHE ahluka ngamashumi kuya emakhulwini ama-millivolt, futhi isixazululo sokugcwalisa siwashintsha nakakhulu la manani. Wonke amandla kagesi akulesi sihloko asho ireferensi yawo. Noma iliphi iphepha elingakwenzi lokhu alikwazi ukusetshenziswa kabusha. Umehluko wesakhiwo phakathi kwalezi zinhlobo ezimbili, i-cation eyisicaba uma iqhathaniswa ne-molecule engathathi hlangothi egobekayo, nawo uyingxenye yalolu daba, futhi ikhasi elihambisana naleli eliphathelene nepheya ye-redox liwuchaza ngokuningiliziwe.

Lokho i-voltammogram ye-methylene blue ekubonisayo ngempela

Ku-electrode ehlanzekile, engamboziwe, yekhabhoni eyingilazi, ekusixazululweni se-phosphate buffer esicishe singathathi hlangothi, i-methylene blue encibilikile ngokuvamile ikhiqiza isiqongo se-anodic esicishe sibe ngu-0.15 kuya ku-0.18 V ohlangothini olunegethivu uma kuqhathaniswa ne-Ag/AgCl, kanye nesiqongo se-cathodic esicishe sibe ngu-0.20 kuya ku-0.25 V ohlangothini olunegethivu uma kuqhathaniswa nereferensi efanayo. Izindawo eziqondile ziyashintsha ngesivinini sokuskena, umlando wendawo engaphezulu, nesixazululo sokugcwalisa ireferensi, futhi isilinganiso sakamuva esitholakala ngokukhululekile sekhabhoni eyingilazi engamboziwe sibeka isiqongo se-cathodic cishe ku-0.18 V ohlangothini olunegethivu ku-pH 7.4 ngaphansi kwezimo zaso.

Leli pheya lichazwa kahle kakhulu njengelibuyiseleka emuva ngokwengxenye. Ipheya eliphelele elibuyiseleka emuva elibandakanya ama-electron amabili belizobonisa iziqongo eziqhelelene cishe ngo-30 mV. Amagagasi e-methylene blue ngokuvamile abanzi futhi awalingani nhlangothi zombili, kanti ukunamathela endaweni engaphezulu kwenza incazelo ibe nzima. Lobo bunzima buyinkomba yokuxilonga, hhayi umsindo wesignali. Umsinga wesiqongo okhula ngokulingana ngokuqondile nesivinini sokuskena ukhomba udayi onamathele endaweni engaphezulu. Umsinga wesiqongo okhula ngempande eyisikwele yesivinini sokuskena ukhomba udayi osabalala usuka esixazululweni. Amarekhodi amaningi angempela ahlanganisa kokubili, yingakho isixazululo esifanayo singakhiqiza ukuphakama kweziqongo okuhlukile ku-electrode esanda kupholishwa nakwesetshenzisiwe.

I-oxygen encibilikile ingeza umsinga wayo we-reduction ebangeni elifanayo, ngakho umsebenzi wokulinganisa amanani ngokuvamile wenziwa ngemva kokukhipha i-oxygen noma ngokucabangela umthelela wayo. Futhi i-methylene blue ingcolisa indawo ye-electrode: udayi onamathele ushintsha indawo engaphezulu kuwo wonke umjikelezo, ngakho ukuhamba kweziqongo ekuskeneni okuphindaphindiwe kuwubufakazi ngesimo se-electrode, hhayi ngento ehlaziywayo.

Ukusuka kudayi oncibilikile kuya ku-electrode eguquliwe

Inzwa yebhayoloji ene-electrode eguqulwe nge-methylene blue iqala ngokubona into elula. Udayi unamathela ngamandla kukhabhoni, ngakho ukucwilisa i-electrode esixazululweni sikadayi sekuyayiguqula. Ukunamathisela okulula futhi kuyindlela yokwakha engazinzile kakhulu, ngoba udayi uyaphuma ubuyele esixazululweni. Konke okunye kulesi sigaba kuyindlela yokubhekana nalokho kuphuma.

Indlela eyamukelwe kakhulu yi-poly(methylene blue) eyenziwe nge-electropolymerization. Ukuhambisa i-electrode emijikelezweni ye-oxidation esixazululweni sikadayi kubeka ifilimu esebenzayo ku-redox, ehlala isendaweni kangcono kakhulu kune-monomer enamathele nje. Inqubo ejwayelekile yohlobo luka-Karyakin isebenzisa cishe u-1 mM kadayi ku-0.02 M we-borate buffer eduze kwe-pH 9.1, kanye no-0.1 M we-potassium chloride, ihambe emijikelezweni ukusuka cishe ku-0.40 V ohlangothini olunegethivu kuya ku-1.20 V ohlangothini oluphozithivu, imijikelezo ecishe ibe ngu-30, njengoba kubhalwe embhalweni wethisisi yase-Durham ochaza le ndlela. I-buffer ene-alkaline ibalulekile: ukukhula kwefilimu kuqhubeka ngezinhlobo ezisesimweni se-oxidation ezikhiqizwa emandleni kagesi aphozithivu, futhi ibanga lokuskena kufanele lifinyelele kuzo.

Ezinye izindlela zokwakha zixazulula izinkinga ezihlukile. Ama-electrode enziwe nge-carbon paste naphrintwe ngesisefo ayeka ukunemba okuthile ukuze abe ngawokusetshenziswa kanye. Izinhlanganisela ezinama-nanotube noma i-graphene zandisa indawo esebenzayo futhi zenze iziqongo zicace. Ama-electrode egolide anezinkomba ezibambelelwe nge-thiol asetshenziselwa izinzwa ze-nucleic acid ezingezansi. Ukubamba udayi ngaphansi kwamafilimu e-Nafion kubambezela ukuphuma kwawo, kodwa kwenze ukusabela kuhambe kancane. Umbuzo womklamo uhlala ufana: iyiphi indlela yokwehluleka oyinqandayo, futhi yini oyidele ukuze wenze lokho.

Umqondo womlamuli: umdluliseli, hhayi i-reagent

Njengomlamuli we-redox ku-cyclic voltammetry ye-methylene blue, udayi oncibilikile usebenza njengomdluliseli wama-electron phakathi kwento ehlaziywayo engashintshisani kalula ngama-electron ne-electrode. Udayi osesimweni se-oxidation wamukela ama-electron ekusabeleni kwamakhemikhali esampula, i-electrode ibuyisela udayi osesimweni se-reduction esimweni se-oxidation, bese umsinga olinganisiwe ukhombisa izinga lokujikeleza kokusabela. Ukugxila okuvamile lapho udayi usabalala ngokukhululekile kungamashumi ama-micromolar, cishe u-10 kuya ku-60, hhayi noma yiliphi inani elijwayelekile elinqunyiwe.

Izinhlobo ezintathu zokusebenza kwamakhemikhali ngokulamula zivela ngokuphindaphindiwe. Udayi ulamula i-oxidation ye-NADH, kuhlanganise nokujikeleza kokusabela okuhlanganiswe nama-enzyme, futhi amafilimu e-poly(methylene blue) asheshisa ukusabela okufanayo nge-electrocatalysis endaweni engaphezulu. Kuma-oxidase ungasebenza njengomamukeli wama-electron wokwenziwa. Ezinhlelweni ze-peroxidase, udayi osesimweni se-reduction udlulisela ama-electron ezintweni eziphakathi nendawo ezinciphisa i-peroxide, okuvumela ukutholwa kwe-hydrogen peroxide emandleni kagesi afakiwe aphansi lapho ukuphazamiseka kuncane khona. Ucwaningo lwe-Chemical Science lwango-2025 lwe-oxidation ye-NADH elamulwayo luchaza le ndlela ngokuningiliziwe. Uma kufakwe udayi omningi, isignali yangemuva yomlamuli nokusebenza kwamakhemikhali e-oxygen kungadlula isignali yokuhlaziya, ngakho ukugxila komlamuli kuyinto elungiswayo ukuze kutholakale ukusebenza okungcono kakhulu, hhayi ukweqisa kwe-reagent.

Izinzwa ze-nucleic acid: lapho ukubopha kuba umsinga

I-methylene blue ibopha i-DNA ngenhlanganisela yokungena phakathi kwezingqimba zayo, ukukhangana kwamashaji kagesi, nokuxhumana okuqondene ne-guanine, ngakho ukuyibiza nje ngento engena phakathi kwezingqimba kunciphisa incazelo yamakhemikhali ayo. Imiklamo yezinzwa iguqula lokho kubopha kube umsinga ngezakhiwo ezimbili ezihlukile, futhi ukuzidida kuyiphutha elivame kakhulu lapho kufundwa le mibhalo.

Emiklamweni engenawo amalebula, udayi okhululekile esixazululweni uhlangana ne-DNA yenkomba eboshelwe endaweni engaphezulu, bese ukuhlangana kwezintambo ze-DNA ezihambelanayo kushintsha isignali. Indlela evamile yokuncipha kwesignali: inkomba enentambo eyodwa iqongelela udayi bese ikhiqiza isiqongo esikhulu, kuyilapho ukuhlangana ukuze kwakheke i-DNA enezintambo ezimbili kushintsha indawo ezungeze udayi bese isignali yehla. Lezi zindlela zivame ukufinyelela emikhawulweni yokuthola esezingeni lama-nanomolar. Esinye isibonelo sakha i-DNA ehambelanayo kuma-carbon nanotube anodonga olulodwa abekwe egolideni, sabika ubudlelwane obuqondile ukusuka ku-100 kuya ku-1000 nM, nomkhawulo wokuthola ocishe ube ngu-7 nM ku-Electroanalysis.

Emiklamweni enamalebula, udayi uboshelwa ngesibopho se-covalent komunye umkhawulo wenkomba, omunye umkhawulo uboshelwe egolideni nge-thiol, bese i-square wave voltammetry ilandelela inkomba yesignali eboshelwe. Izinzwa ze-electrochemical aptamer ezisekelwe ekugoqekeni zandisa lo mqondo: ukubopha into okuhloswe ngayo kushintsha ukwakheka kwe-aptamer bese kuhambisa inkomba yesignali uma iqhathaniswa ne-electrode. Inzwa ye-ochratoxin A esebenzisa i-aptamer enamalebula amabili, i-thiol nodayi, egolideni yabika ibanga lika-0.1 kuya ku-1000 pg per mL, nomkhawulo wokuthola ocishe ube ngu-0.095 pg per mL, yashicilelwa ku-Analytica Chimica Acta.

Lo mehluko ubalulekile ekutholeni nasekulungiseni izinkinga. Ezindleleni ezingenawo amalebula, udayi uyingxenye yesixazululo enokugxila kwayo nokuncika kwayo ku-pH. Ezindleleni ezinamalebula, udayi uyingxenye yenkomba, futhi ukushintsha kwesignali kubika ibanga nokunyakaza, hhayi ukumuncwa kukadayi.

Izibonelo zama-enzyme nezinhlanganisela

Amafilimu e-poly(methylene blue) aphinde abambe izinzwa zama-enzyme. Enye inzwa ye-ammonium yahlanganisa i-electrode ephrintwe ngesisefo nama-nanoparticle egolide nefilimu kadayi, yase imboza phezulu ngesistimu yokusabela ye-glutamate dehydrogenase. Ifilimu yenza i-oxidation ye-NADH kuyilapho i-enzyme iyisebenzisa ngokulingana ne-ammonium: u-0 kuya ku-300 micromolar, nomkhawulo wokuthola ocishe ube ngu-0.65 micromolar, njengoba kubikiwe ku-Biosensors. Umkhakha wonke uchazwa ekubuyekezweni kwango-2025 kokusetshenziswa kukadayi ekutholeni nge-electrochemistry ku-Analytica Chimica Acta.

Izimo okufanele zihambisane nawo wonke umphumela

Umbhalo oyireferensi ohambisana nalona omayelana nokuhlola amanani uhlanganisa ngokujwayelekile ukuqikelela ekulinganiseni amathuluzi. Ngokuqondene nemiphumela ye-electrochemistry, le mininingwane kufanele ibe kuwo wonke amarekhodi elabhorethri:

Inkomba yesignali ayiyona indlela yokwelapha

Umehluko wokugcina yiwona leli khasi elenzelwe ukuwugcizelela. Ukwehla kwesiqongo se-square wave lapho kuhlangana izintambo ze-DNA ezihambelanayo kufakazela ukuthi ilebula ye-redox ihambile noma ukuthi ukubopha kukadayi kushintshile. Akufakazeli lutho ngalokho i-methylene blue ekwenzayo esigulini. Amakhemikhali okulinganisa nokusebenza kwebhayoloji kwabelana nge-molecule kuphela: ukugxila okuhlukile, izinhlanganisela zesampula ezihlukile, nezimo ezihlukile lapho ulwelwesi nama-enzyme kuthatha indawo yama-electrode aphikisayo. Gcina imibuzo yokwelapha emakhasini okusebenza kwebhayoloji, futhi ugcine izimangalo zezinzwa zixhumene ne-electrode, i-buffer, nendlela ezikhiqize ngayo imiphumela. Ilebula ye-redox iyinkomba yesignali. Izinkomba zesignali zichaza ukuhlola, hhayi umzimba.