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Peroral vaccine delivery systems based on non-ionic surfactant vesicles
Poster Session P2: Monday 16 September
S138
rcirase Drub: delivery using liposomcs hares on controlled Metronidazole binding and competitive process _ leakage ~1‘ druy were examined The binding constant for InetronidaAe - liposome - serum albumin has been evaluated and compared \rith those for metronidazole serum albumin and metronidarole - liposomr system Equilibrium dialysis were carried WI at 26 C’ for 24 II in water bath The concentration of free drug was determined by U\’ spectroscopy al 320 nm Binding data were represented in a graph of moles of bound hyand per mole of Imacromolecule as a function of free l&and concentration The interaction or protein with liposomes can cause an increase in the rate of diffusion of mekonidazolc molecules across the liposome bilayers Interaction of liposomes containing druy molecules \rith serum albumin components will cause an increased leakage of druy from liposomes
The majority of infectious diseases is encountered through the large area of the body’s mucosal surfaces, e. g. gastro-intestinal tract, respiratory tract and uro-genital tract. These surfaces are protected by their own secretory immune system which cannot be activated efficiently by the parenteral route. Oral vaccination, however, activates the gastro-intestinal system and also other mucosal sites and offers a number of further advantages over the parenteral route, including ease and convenience of administration, increased patient compliance, reduced costs and minimal side effects. In this study the intestinal uptake of a new vaccine delivery system based on nonIonic surfactant vesicles (niosomes) is followed by confocal laser scanning microscopy (CLSM) and by measuring the specific antibody responses. Small unilamellar vesicles were prepared by probe sonication from sucrose ester surfactants (Wasag’7 or Wasag’l5), cholesterol and dicetyl phosphate in a molar ratio 4:5:1_ The sucrose ester surfactants used in this study form gel state bilayers at 37 “C and have been chosen due to their easy biodegradability and very low toxicity. Fluorescent markers (Bodipy’, ftuorescein labelled ovalbumin) have been incorporated into the lipophilic bilayer and the aqueous core of the vesicles, respectively. The model protein ovalbumin was encapsulated by using the lyophilization method described in [1] The freeze-dried membranes were resuspended with ovalbumin (10 mg I ml] dissolved in phosphate buffered saline (PhEur, pH 7.4). Female BALBlc mice (age: 6 - 8 weeks) were starved over night and fed intragastrically 0.5 ml of the various vesicle and control formulations. The in vivo uptake into the Peyer’s Patches was monitored after two hours and longer time intervals by CLSM. The specific antibody responses in serum, saliva and intestinal washings were detected by ELISA. Only administration of encapsulated ovalbumin resulted in a good uptake and antibody production. Reference [f] C. KIREY and G. GREGORIADIS,
UK 8405328
Recently, there has been considerable interest in the use of o/w microemulsions (ME) as drug delivery vehicles. Unfortunately, most work to date has examined the preparation of ME using pharmaceutically unacceptable ingredients. In this study we have attempted to redress this inbalance by investigating the formation of o/w ME involving a fatty acid ethyl ester and nonionic SAA possessing either an amine-N-oxide (AO) or a decaoxyethylene head group joined to a dodecyl (C,,) or an oleyl (C,, ,) chain and containing an ethyl ester of a fatty acid. The area of ME existence were established as reported previously
(Malcolmson and Lawrence, Cc&aids a Surfaces 6: Bttintsdacss 4:97-W
The table shows the calculated critical packing parameter (CPP) of the SAA (a parameter that has been used to predict ME formation) and the maximum amount of oil incorporated and the SAA concentration(s) at which this occured. With the exception of C,, ,E,,, all SAA examined exhibited the greatest capacity for the smallest molecular volume oil, ethyl butyrate (EB) and the least for the largest molecular volume oil, ethyl oleate (EO). Interestingly, this trend was reversed for C,,,E,,, with EO being taken up to the greatest extent. This is the first time such a result has been reported and it may be a consequence of the nature of the interaction between the hydrophobic ains of the SAA and an oil of similar length. 19%).
Inspection of the CPP shows that this parameter cannot be used to predict whether a particular SAA will form a ME. For example the two A0 SAA have a very similar CPP, yet one (C,$O) readily forms ME, while the other (C,,,AO) does not. The formation of ME is not straightfomard and therefore cannot easily be predicted.
S138
rcirase Drub: delivery using liposomcs hares on controlled Metronidazole binding and competitive process _ leakage ~1‘ druy were examined The binding constant for InetronidaAe - liposome - serum albumin has been evaluated and compared \rith those for metronidazole serum albumin and metronidarole - liposomr system Equilibrium dialysis were carried WI at 26 C’ for 24 II in water bath The concentration of free drug was determined by U\’ spectroscopy al 320 nm Binding data were represented in a graph of moles of bound hyand per mole of Imacromolecule as a function of free l&and concentration The interaction or protein with liposomes can cause an increase in the rate of diffusion of mekonidazolc molecules across the liposome bilayers Interaction of liposomes containing druy molecules \rith serum albumin components will cause an increased leakage of druy from liposomes
The majority of infectious diseases is encountered through the large area of the body’s mucosal surfaces, e. g. gastro-intestinal tract, respiratory tract and uro-genital tract. These surfaces are protected by their own secretory immune system which cannot be activated efficiently by the parenteral route. Oral vaccination, however, activates the gastro-intestinal system and also other mucosal sites and offers a number of further advantages over the parenteral route, including ease and convenience of administration, increased patient compliance, reduced costs and minimal side effects. In this study the intestinal uptake of a new vaccine delivery system based on nonIonic surfactant vesicles (niosomes) is followed by confocal laser scanning microscopy (CLSM) and by measuring the specific antibody responses. Small unilamellar vesicles were prepared by probe sonication from sucrose ester surfactants (Wasag’7 or Wasag’l5), cholesterol and dicetyl phosphate in a molar ratio 4:5:1_ The sucrose ester surfactants used in this study form gel state bilayers at 37 “C and have been chosen due to their easy biodegradability and very low toxicity. Fluorescent markers (Bodipy’, ftuorescein labelled ovalbumin) have been incorporated into the lipophilic bilayer and the aqueous core of the vesicles, respectively. The model protein ovalbumin was encapsulated by using the lyophilization method described in [1] The freeze-dried membranes were resuspended with ovalbumin (10 mg I ml] dissolved in phosphate buffered saline (PhEur, pH 7.4). Female BALBlc mice (age: 6 - 8 weeks) were starved over night and fed intragastrically 0.5 ml of the various vesicle and control formulations. The in vivo uptake into the Peyer’s Patches was monitored after two hours and longer time intervals by CLSM. The specific antibody responses in serum, saliva and intestinal washings were detected by ELISA. Only administration of encapsulated ovalbumin resulted in a good uptake and antibody production. Reference [f] C. KIREY and G. GREGORIADIS,
UK 8405328
Recently, there has been considerable interest in the use of o/w microemulsions (ME) as drug delivery vehicles. Unfortunately, most work to date has examined the preparation of ME using pharmaceutically unacceptable ingredients. In this study we have attempted to redress this inbalance by investigating the formation of o/w ME involving a fatty acid ethyl ester and nonionic SAA possessing either an amine-N-oxide (AO) or a decaoxyethylene head group joined to a dodecyl (C,,) or an oleyl (C,, ,) chain and containing an ethyl ester of a fatty acid. The area of ME existence were established as reported previously
(Malcolmson and Lawrence, Cc&aids a Surfaces 6: Bttintsdacss 4:97-W
The table shows the calculated critical packing parameter (CPP) of the SAA (a parameter that has been used to predict ME formation) and the maximum amount of oil incorporated and the SAA concentration(s) at which this occured. With the exception of C,, ,E,,, all SAA examined exhibited the greatest capacity for the smallest molecular volume oil, ethyl butyrate (EB) and the least for the largest molecular volume oil, ethyl oleate (EO). Interestingly, this trend was reversed for C,,,E,,, with EO being taken up to the greatest extent. This is the first time such a result has been reported and it may be a consequence of the nature of the interaction between the hydrophobic ains of the SAA and an oil of similar length. 19%).
Inspection of the CPP shows that this parameter cannot be used to predict whether a particular SAA will form a ME. For example the two A0 SAA have a very similar CPP, yet one (C,$O) readily forms ME, while the other (C,,,AO) does not. The formation of ME is not straightfomard and therefore cannot easily be predicted.