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Title

INVESTIGATION OF DOPAMINE ENCAPSULATION IN LIPOSOME AND ITS ELECTROCHEMICAL DETERMINATION

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Abstract

LIPOSOMES ARE ARTIFICIAL MICROSCOPIC VESICLES COMPOSED OF A LIPID BILAYER IN WHICH THE HYDROPHOBIC CHAINS OF THE LIPIDS ARE FORMING THE BILAYER, AND THE POLAR HEAD GROUPS OF THE LIPIDS ORIENTING TOWARDS THE EXTRA VESICULAR SOLUTION AND INNER CAVITY. LIPOSOMES HAVE BEEN WIDELY USED IN DRUG DELIVERY SUCCESSFULLY [1]. IN A SIMILAR WAY TO THEIR APPLICATION AS A CARRIER FOR DRUGS, LIPOSOMES CAN ACT AS A CARRIER FOR A WIDE RANGE OF SIGNALING MOLECULES ESPECIALLY IN ELECTROCHEMISTRY. THE INNER CAVITY AND OR SPACE BETWEEN BILAYER CAN BE USED FOR ENCAPSULATING HYDROPHILIC AND HYDROPHOBIC COMPOUNDS, RESPECTIVELY [2]. IN THIS STUDY WE INVESTIGATED THE ENCAPSULATION OF DOPAMINE HYDROCHLORIDE IN LIPOSOMES COMPOSED OF LECITHIN AND CHOLESTEROL. THE LIPOSOMES WERE PREPARED FROM LECITHIN: CHOLESTEROL (10:1 MOLAR RATIO) THROUGH THIN FILM HYDRATION METHOD [3]. DOPAMINE HYDROCHLORIDE AS HYDROPHILIC COMPOUND WAS SUCCESSFULLY ENCAPSULATED DURING LIPOSOME FORMATION STEP AND THE ENCAPSULATION EFFICIENCY WAS INVESTIGATED USING  LMAX OF DOPAMINE AT 280 NM. THE ELECTROCHEMICAL STUDIES WERE CARRIED OUT IN SAMA 500 ELECTROANALYSER SYSTEM USING CYCLIC VOLTAMMETRY (CV) AND DIFFERENTIAL PULSE VOLTAMMETRY (DPV) TECHNIQUES WITH A MULTI WALL CARBON NANO TUBE MODIFIED GLASSY CARBONE ELECTRODE (MWCNTS@GCE) AS THE WORKING ELECTRODE AND SATURATED CALOMEL ELECTRODE AND PLATINUM WIRE AS REFERENCE AND COUNTER ELECTRODES, RESPECTIVELY. SPIKING STUDY WAS ALSO DONE. FOR THE RELEASING OF ENCAPSULATED DOPAMINE, TWO METHODS WERE INVESTIGATED: RELEASING BY TRITON-X-100 AND METHANOL. THE ENCAPSULATION EFFICIENCY OF LIPOSOME WAS CALCULATED AS %EFF =CIN-CF/CIN 100 IN WHICH CIN IS INITIAL CONCENTRATION OF DOPAMINE USED FOR ENCAPSULATION AND CF IS THE FINAL CONCENTRATION OF DOPAMINE IN OUTER SOLUTION AFTER ENCAPSULATION. BASED ON THE ABSORBANCE OF DOPAMINE AT LMAX= 280 NM, A CALIBRATION CURVE WAS DEVELOPED AND THE CONCENTRATION OF DOPAMINE AND THE ENCAPSULATION EFFICIENCY WERE CALCULATED. WITH INCREASING THE TOTAL LIPID AND CHOLESTEROL FROM 30 MG TO 60 MG THE % EFF WAS INCREASED FROM %33 .TO %80. THE MEAN SIZE OF LIPOSOMES WAS OBTAINED 127 NM BY DYNAMIC LIGHT SCATTERING (DLS). THE MWCNTS@GCE HAS REMARKABLE SIGNAL FOR DOPAMINE IN COMPARED TO BARE GCE DUO TO ACTIVE SURFACE ENHANCEMENT AND ELECTROCATALYTIC EFFECT OF MWCNTS. A CALIBRATION CURVE FOR DETERMINATION OF DOPAMINE WITH MWCNTS@GCE WAS ALSO DEVELOPED USING DPV AND THE LIMIT OF DETECTION AND LINEAR RANGE WERE OBTAINED 88 NM AND 3-20 MM, RESPECTIVELY. FOR RELEASING OF ENCAPSULATED DOPAMINE TWO METHODS WERE INVESTIGATED: TRITON-X-100 AND AND METHANOL. TRITON X-100 CAUSED THE REDUCTION OF SIGNAL IN WHICH THE SIGNAL OF RELEASED DOPAMINE CANNOT BE MEASURED BUT WITH USING METHANOL THE MEASUREMENT WAS DONE SUCCESSFULLY. THE RESULTS OF SPIKING SHOWED GOOD RECOVERY VALUES THAT SHOWED THE DEVELOPED METHOD CAN BE USED FOR ELECTROCHEMICAL SIGNAL ENHANCING IN APPLICATIONS SUCH AS BIOSENSORS.

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