Transdermal Iontophoresis : Delivery Control by Ion-Exchange Fibers and Nanocarriers

Biological variation and poor transport efficacy are the major concerns in the development of novel iontophoretic drug delivery systems for the transdermal administration of therapeutics. One possibility to overcome these limitations would be to load the drug in interest into a reservoir system such as ion-exchange fibers or nanocarriers prior administration. More precise and homogenous control of drug release and the following transdermal iontophoretic permeation could be obtained as the transdermal device/patch would determine the rate of drug transfer instead of the skin, leading to smaller inter- and intrasubject variability. In addition, the range of molecules delivered by iontophoresis can be expanded as charges could be imparted to neutral drugs by encapsulating them in charged drug carriers. Other benefits raising from such combined systems include enhanced drug transport into or across the skin, improved drug stability and decreased local side effects on skin. The aim of this thesis was to study in vitro the applicability of systems that combine iontophoresis and either drug-loaded ion-exchange fibers or nanocarriers for the controlled transdermal delivery of therapeutics. Firstly, drug reservoirs based on cation-exchange fibers were utilized to retard drug release and provide additional control into transdermal transport of a small molecular drug and a peptide. The drug release kinetics could be modified by the choice of the fiber type or the ionic composition of the external solution. The application of pulsed current iontophoresis instead of conventional constant current led to increased transport efficiency of a cationic hydrophobic peptide that has a tendency to adsorb into skin and inhibit electroosmosis as its main transport mechanism. In addition, drug delivery systems combining iontophoresis and nanoencapsulation into polymeric nanoparticles or lipid vesicles for the controlled transdermal delivery of lipophilic or hydrophilic model compound were developed and tested. Although the obtained nanocarriers were considered as suitable for transdermal iontophoretic administration, regarding the colloidal properties, stability and release kinetics, no clear advantage was observed with respect to drug permeation from free drug formulation. Throughout the thesis, the impact of formulation parameters and current type on drug transport efficiency was monitored. Iontophoretic transdermal drug delivery from polymeric nanoparticle-based formulations but not from lipid vesicular nanocarriers was improved by the application of pulsed current. In conclusion, binding the drug molecules prior iontophoresis into reservoir based on ion-exchange material or nanocarriers is a promising approach to be utilized in controlled transdermal delivery, although the comprehensive evaluation of full potential of such systems tailored for specific drug warrants further investigation in the future.Ihon kautta tapahtuvan lääkkeenannostelun suuria haittapuolia ovat permeaatiotulosten suuri hajonta ja lkääkeaineiden huono kulkeutuminen ihon läpi. Yksi tapa päästä näiden haasteiden yli on ladata lääkeaineita erilaisiin varastoihin , kuten ioninvaihtokuituihin tai nanokantajiin. Hallitumpi ja tasaisempi lääkkeenvapautus on mahdollista käyttämällä pientä sähkövirtaa eli iontoforeettista lääkkeenkuljetusta siirtämään lääke hallitusti ihon lävitse säädetyllä nopeudella. Tämä myös vähentää potilaiden välisiä ja käyttökertojen välisiä vaihteluita lääkeannostelussa. Erilaiset varatut kantajat voivat laajentaa iontoforeesiin soveltuvien lääkeaineiden kirjoa, kun itse lääkeaineen ei tarvitse olla varattu. Tämä voi samalla myös vähentää lääkeaineiden sivuvaikutuksia iholla ja parantaa niiden säilyvyyttä. Tässä tohtorin väitöskirjatyössä tutkittiin järjestelyitä, jossa samanaikaisesti iontoforeesin kanssa käytettiin erilaisia lääkkeenvapautumiseen vaikuttavia kantajia, kuten ioninvaihtokuituja sekä erilaisia nanokantajia. Aluksi lääkevarastoina käytettiin kationinvaihtokuituja. Nämä hidastivat lääkkeenvapautusta ja tarjosivat erillisen tavan hallita lääkkeenvapautumis ja -kuljetusnopeutta. Kuidun tyyppi ja vastaionien valinta vaikuttivat tähän nopeuteen. Pulssitettu iontoforeesi oli tavallista vakiovirtaiontoforeesia tehokkaampi tapa kuljettaa lääkeaineita ihon läpi tilanteessa, jossa kationinen peptidi sitoutuu ihon rakenteisiin. Tämä yleensä vähentää ihon elektro-osomoosia joka on pääasiallinen kuljetusmekanismi suuremmille molekyyleille. Jatkotutkimuksissa tutkittiin iontoforeesin vaikutusta polymeerisiin tai lipidisiin nanokapseleihin pakattujen lääkeaineiden ihoannosteluun. Kantajien näytettiin soveltuvan iontoforeettiseen annosteluun ja niiden välillä havaittiin selkeitä eroja, mutta mitkään niistä eivät tarjonneet selkeitä etuja verrattuna liuosmuotoiseen lääkeainevarastoon, jossa lääkeaineet olivat jo alunperin vapaasti liuenneet. Lyhyesti, lääkeaineiden sitominen erilliseen lääkekantajaan tai -varastoon iontoforeettisen lääkeannostelun yhteydessä on lupaava lähestymistapa säädeltyyn lääkkeenvapautumiseen. Toistaiseksi kuitenkin vielä puuttuu annostelua selvästi tehostava kantaja. Annostelu on myös hyvin riippuvaista itse lääkemolekyylistä, mikä hankaloittaa ennustettavaa lääkekehitystä. Jatkossa tutkimuksen oletetaan keskittyvän yksittäisiin tapauksiin, joiden optimointi voi selkeästi hyötyä tässä väitöskirjassa kehitetyistä menetelmistä ja tiedoista

Inhibitory activity of the isoflavone Biochanin A on intracellular bacteria of genus Chlamydia and initial development of a buccal formulation

Peer reviewe

IC₅₀ values (µM) of isoflavones on <i>C. pneumoniae</i> and <i>C. trachomatis</i> inclusion counts.

<p>*IC₅₀ values were determined by treating the infected cell cultures with isoflavones at concentration 100, 75, 50, 25, 10 and 5 µM and determining the inclusion counts as described in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0115115#s2" target="_blank">Materials and methods</a>. -  =  no inhibition. A statistically significant difference in <i>C</i>. <i>pneumoniae</i> IC₅₀ values was observed between biochanin A and genistein (p<0.05, Student's t-test)</p><p>IC₅₀ values (µM) of isoflavones on <i>C. pneumoniae</i> and <i>C. trachomatis</i> inclusion counts.</p

X-ray diffraction and DSC measurements of film formulations.

<p>A) X-ray diffraction patterns of (a) biochanin A powder, (b) genistein powder, (c) HPMC powder, (d) film Fii, (e) blank film Faa without biochanin A, (f) film Faa, (g) film Fjj and (h) physical mixture of formulation Faa. B) DSC thermograms of (a) biochanin A powder, (b) HPMC powder, (c) film Fii, (d) blank film Faa without biochanin A, (e) film Faa, (f) film Fjj and (g) physical mixture of formulation Faa.</p

Effect of isoflavones on <i>C. trachomatis</i> inclusion size.

<p>A) Immunofluorescence images of <i>C. trachomatis</i> infected HeLa cells (untreated and treated with 100 or 10 µM biochanin A). <i>Chlamydia</i> inclusions are stained in green (polyclonal rabbit antibody raised against formalin fixed <i>C</i>. <i>trachomatis</i> elementary bodies <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0115115#pone.0115115-Marwaha1" target="_blank">[30]</a>) and host cell nuclei are stained in blue with DAPI. B) Quantitation of average inclusion sizes in <i>C. trachomatis</i> infections treated with the isoflavones. Inclusion sizes are expressed as relative units proportional to the untreated controls. In a pairwise comparison of different concentrations, the mean inclusion size in biochanin A, genistein and genistin treated samples were statistically significantly smaller than in formononetin, daidzein and daidzin treated samples, respectively (p<0.05, Student's t-test).</p

Composition of sublingual films of biochanin A.

<p>*Quantities are expressed in %w/w of polymer; **Quantities are expressed in ratio of biochanin A to excipient.</p><p>Composition of sublingual films of biochanin A.</p

Properties of sublingual films of biochanin A. Data are presented as mean ± standard deviation (^an = 12 and ^bn = 3–4).

<p>*analysis was done with small parts of the film (n = 4).</p><p>Properties of sublingual films of biochanin A. Data are presented as mean ± standard deviation (^an = 12 and ^bn = 3–4).</p

Permeability of biochanin A across porcine buccal mucosa.

<p>Cumulative amount of biochanin A was measured from the acceptor compartment of the diffusion cell.</p

Chemical structures of the six isoflavones included in the study.

<p>Chemical structures of the six isoflavones included in the study.</p

Dissolution profiles of biochanin A from buccal films of different composition, physical mixture (PM, corresponding to formulation Faa) and powder at pH 6.8. Data are presented as mean ± standard deviation (n = 3).

<p>Dissolution profiles of biochanin A from buccal films of different composition, physical mixture (PM, corresponding to formulation Faa) and powder at pH 6.8. Data are presented as mean ± standard deviation (n = 3).</p