Nanocarriers from GRAS Zein Proteins to Encapsulate Hydrophobic Actives.

One factor limiting the expansion of nanomedicines has been the high cost of the materials and processes required for their production. We present a continuous, scalable, low cost nanoencapsulation process, Flash Nanoprecipitation (FNP) that enables the production of nanocarriers (NCs) with a narrow size distribution using zein corn proteins. Zein is a low cost, GRAS protein (having the FDA status of "Generally Regarded as Safe") currently used in food applications, which acts as an effective encapsulant for hydrophobic compounds using FNP. The four-stream FNP configuration allows the encapsulation of very hydrophobic compounds in a way that is not possible with previous precipitation processes. We present the encapsulation of several model active compounds with as high as 45 wt % drug loading with respect to zein concentration into ∼100 nm nanocarriers. Three examples are presented: (1) the pro-drug antioxidant, vitamin E-acetate, (2) an anticholera quorum-sensing modulator CAI-1 ((S)-3-hydroxytridecan-4-one; CAI-1 that reduces Vibrio cholerae virulence by modulating cellular communication), and (3) hydrophobic fluorescent dyes with a range of hydrophobicities. The specific interaction between zein and the milk protein, sodium caseinate, provides stabilization of the NCs in PBS, LB medium, and in pH 2 solutions. The stability and size changes in the three media provide information on the mechanism of assembly of the zein/active/casein NC.

Alternative vaccine administration by powder injection: Needle-free dermal delivery of the glycoconjugate meningococcal group Y vaccine.

Powder-injectors use gas propulsion to deposit lyophilised drug or vaccine particles in the epidermal and sub epidermal layers of the skin. We prepared dry-powder (Tg = 45.2 ± 0.5°C) microparticles (58.1 µm) of a MenY-CRM197 glyconjugate vaccine (0.5% wt.) for intradermal needle-free powder injection (NFPI). SFD used ultrasound atomisation of the liquid vaccine-containing excipient feed, followed by lyophilisation above the glass transition temperature (Tg' = - 29.9 ± 0.3°C). This resulted in robust particles (density~ 0.53 ±0.09 g/cm3) with a narrow volume size distribution (mean diameter 58.1 µm, and span = 1.2), and an impact parameter (ρvr ~ 11.5 kg/m·s) sufficient to breach the Stratum corneum (sc). The trehalose, manitol, dextran (10 kDa), dextran (150 kDa) formulation, or TMDD (3:3:3:1), protected the MenY-CRM197 glyconjugate during SFD with minimal loss, no detectable chemical degradation or physical aggregation. In a capsular group Y Neisseria meningitidis serum bactericidal assay (SBA) with human serum complement, the needle free vaccine, which contained no alum adjuvant, induced functional protective antibody responses in vivo of similar magnitude to the conventional vaccine injected by hypodermic needle and syringe and containing alum adjuvant. These results demonstrate that needle-free vaccination is both technically and immunologically valid, and could be considered for vaccines in development.

Needle-Free Dermal Delivery of a Diphtheria Toxin CRM197 Mutant on Potassium-Doped Hydroxyapatite Microparticles.

Injections with a hypodermic needle and syringe (HNS) are the current standard of care globally, but the use of needles is not without limitation. While a plethora of needle-free injection devices exist, vaccine reformulation is costly and presents a barrier to their widespread clinical application. To provide a simple, needle-free, and broad-spectrum protein antigen delivery platform, we developed novel potassium-doped hydroxyapatite (K-Hap) microparticles with improved protein loading capabilities that can provide sustained local antigen presentation and release. K-Hap showed increased protein adsorption over regular hydroxyapatite (P < 0.001), good structural retention of the model antigen (CRM197) with 1% decrease in α-helix content and no change in ß-sheet content upon adsorption, and sustained release in vitro. Needle-free intradermal powder inoculation with K-Hap-CRM197 induced significantly higher IgG1 geometric mean titers (GMTs) than IgG2a GMTs in a BALB/c mouse model (P < 0.001) and induced IgG titer levels that were not different from the current clinical standard (P > 0.05), namely, alum-adsorbed CRM197 by intramuscular (i.m.) delivery. The presented results suggest that K-Hap microparticles may be used as a novel needle-free delivery vehicle for some protein antigens.

Intradermal powder immunization with protein-containing vaccines.

The central importance for global public health policy of delivering life-saving vaccines for all children makes the development of efficacious and safe needle-free alternatives to hypodermic needles, preferably in a thermostable form, a matter of pressing urgency. This paper comprehensively reviews past in vivo studies on intradermal powder immunization with vaccine formulations that do not require refrigeration. Particular emphasis is given to the immune response in relation to antigen adjuvantation. While needle-free intradermal delivery of vaccines induces a predominantly Th2-type immune response, adjuvants powerfully enhance and modulate the magnitude and nature of the elicited immune response at various effector sites.