Vaccines are the most ideal means to resist microbial infections. It has the lowest cost and minimal damage to the body. The infectious diseases that have been eradicated from humans to date have been achieved through vaccines. There is no precedent in the world for the eradication of an infectious disease by non-vaccine methods. The immune effect of a vaccine depends on many aspects such as the choice of antigen and adjuvant, the route of administration and the delivery system. Among them, vaccine delivery system refers to a class of substances that can carry antigenic substances to the body's immune system, where they are stored and exert their antigenic effects for a longer period. The advantages of vaccine delivery systems are not only in maintaining the long-term effectiveness of the vaccine and reducing the number of immunizations, but also in slow/controlled release delivery, targeted delivery, pulsed or self-regulated delivery, etc. Characterization of vaccine delivery systems can be challenging. Our professional vaccine development team provides characterization services for common delivery systems.
Common vaccine delivery systems
Vaccine delivery systems can be classified as follows.
- Liposomal delivery systems
Liposomes and their derivatives "lipoplexes" (liposome/DNA complexes) are hollow spherical constructs of phospholipid bilayers capable of entrapping hydrophilic moieties in the aqueous compartment and hydrophobic moieties in the lipid bilayers with cholesterol imparting rigidity to the bilayer. Liposomes were first used for topical application in the early 1980s by Mezei and Gulasekharam . These studies indicated increased bioavailability of liposome-encapsulated drug within the skin and, at the same time, lower drug levels in the blood indicating an advantageous location of the drug at the target site similarly to a depot.
Figure 1. Liposomes act as vaccine delivery systems
- Polymeric nanoparticle delivery systems
Polymeric nanoparticles stand out as a key tool to improve drug bioavailability or specific delivery at the site of action. Due to the small size of polymeric nanoparticles, they are preferentially taken up by the mucosa associated lymphoid tissue. They are extensively reviewed for nasal and oral delivery of vaccines. Limited doses of antigen are sufficient to induce effective immunization. Hence, the use of nanoparticles for oral delivery of antigens is suitable because of their ability to release proteins and to protect them from enzymatic degradation.
Figure 2. Polymeric nanoparticles act as vaccine delivery systems
- Micellar delivery systems
Micelles have been well investigated as potential antigen carriers. Micelles are self-aggregated clusters of amphiphilic surfactant molecules. Surfactants above critical micellar concentration orient themselves into micellar structures in order to avoid contact with incompatible external phase and can enclose lipophilic cavity or hydrophilic cavity (reverse micelle) thus promoting entrapment of antigens for their delivery into the body.
Figure 3. Micelles act as vaccine delivery systems 
- Emulsion delivery systems
Emulsions are heterogenous liquid systems may be water-in-oil emulsions, oil-in-water emulsions, or more complex systems such as multiple emulsions, multilayer emulsions, solid lipid particles or filled hydrogel particles. Antigens are dissolved in a water phase and emulsified in the oil in the presence of an appropriate emulsifier.
Figure 4. Different types of delivery systems that can be created based on emulsion technology 
- Dendrimer-based delivery systems
Dendrimers are branched, synthetic polymers with layered architectures. By combining the multifunctional polymeric material with a biologically active substance in an aqueous loading environment, the carrier system can be administered as a drug delivery vehicle to a human subject.
Figure 5. Dendrimers act as vaccine delivery systems
Some important properties of vaccine delivery systems need to be carefully characterized, including size and PDI, zeta potential, surface morphology and stability. Alfa Chemistry provides characterization services for the above-mentioned vaccine delivery systems. In order to better characterize the vaccine delivery system, we are also equipped with several technical platforms. These platforms include but are not limited to the following.
Why choose us
Proper characterization of vaccine delivery systems is critical not only for studying the synthesis of delivery systems, but also for controlling their quality to meet the requirement of the application. By utilizing our well-equipped laboratories and experienced experts to work with your team, Alfa Chemistry offers efficient delivery system characterization services. If you have any questions about vaccine delivery systems, please feel free to contact us. Alfa Chemistry is always your project partner.
- Mezei, M.; et al. Liposomes-a selective drug delivery system for the topical route of administration. Lotion dosage form. Life Sci. 1980, 26: 1473-1477.
- Trimaille, T.; et al. Micelle-based adjuvants for subunit vaccine delivery. Vaccines. 2015, 3(4): 803-813.
- Weiss, J.; et al. Emulsion‐based delivery systems for lipophilic bioactive components. Journal of food science. 2007,72: R109-R124.
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