An investigation of alkaline phosphatase enzymatic activity after electrospinning and electrospraying

The high target specificity and multifunctionality of proteins has led to great interest in their clinical use. To this
end, the development of delivery systems capable of preserving their bioactivity and improving bioavailability is
pivotal to achieve high effectiveness and satisfactory therapeutic outcomes. Electrohydrodynamic (EHD) techniques,
namely electrospinning and electrospraying, have been widely explored for protein encapsulation and
delivery. In this work, monoaxial and coaxial electrospinning and electrospraying were used to encapsulate
alkaline phosphatase (ALP) into poly(ethylene oxide) fibres and particles, respectively, and the effects of the
processing techniques on the integrity and bioactivity of the enzyme were assessed. A full morphological and
physicochemical characterisation of the blend and core-shell products was performed. ALP was successfully
encapsulated within monolithic and core-shell electrospun fibres and electrosprayed particles, with drug loadings
and encapsulation efficiencies of up to 21% and 99%, respectively. Monoaxial and coaxial electrospinning
were equally effective in preserving ALP function, leading to no activity loss compared to fresh aqueous solutions
of the enzyme. While the same result was observed for monoaxial electrospraying, coaxial electrospraying of ALP
caused a 40% reduction in its bioactivity, which was attributed to the high voltage (22.5 kV) used during
processing. This demonstrates that choosing between blend and coaxial EHD processing for protein encapsulation
is not always straightforward, being highly dependent on the chosen therapeutic agent and the effects of the
processing conditions on its bioactivity.