Hybrid and antimicrobial nanoparticles (NPs) of poly (methyl methacrylate) (PMMA) in the presence of poly (diallyl dimethyl ammonium) chloride (PDDA) were previously obtained by emulsion polymerization in absence of surfactant with low conversion. In the presence of amphiphiles such as cetyl trimethyl ammonium bromide (CTAB), dioctadecyl dimethyl ammonium bromide (DODAB) or soybean lecithin, we found that conversion increased substantially. In this work, the effect of the amphiphiles on the NPs core-shell structure and on the antimicrobial activity of the NPs was evaluated. NPs dispersions casted on silicon wafers, glass coverslips or polystyrene substrates were also used to obtain antimicrobial coatings. Methods for characterizing the dispersions and coatings were based on scanning electron microscopy, dynamic light scattering, determination of thickness, rugosity, and wettability for the coatings and determination of colony-forming unities (log CFU/mL) of microbia after 1 h interaction with the coatings or dispersions. The amphiphiles used during PMMA/PDDA/amphiphile NPs synthesis reduced the thickness of the NPs PDDA shell surrounding each particle. The antimicrobial activity of the dispersions and coatings were due to PDDA—the amphiphiles were either washed out by dialysis or remained in the PMMA polymeric core of the NPs. The most active NPs and coatings were those of PMMA/PDDA/CTAB—the corresponding coatings showed the highest rugosity and total surface area to interact with the microbes. The dispersions and coatings obtained by casting of the NPs dispersions onto silicon wafers were hydrophilic and exhibited microbicidal activity against Escherichia coli, Staphylococcus aureus, and Candida albicans. In addition, a major effect of reduction in particle size revealed the suitability of nanometric and cationic NPs (sizes below 100 nm) represented by PMMA/PDDA/CTAB NPs to yield maximal microbicidal activity from films and dispersions against all microbia tested. The reduction of cell viability by coatings and dispersions amounted to 6–8 logs from [PDDA] ≥ minimal microbicidal concentration.

Since antigens are negatively charged, they combine well with positively charged adjuvants. Here, ovalbumin (OVA) (0.1 mg·mL −1 ) and poly (diallyldimethylammonium chloride) (PDDA) (0.01 mg·mL −1 ) yielded PDDA/OVA assemblies characterized by dynamic light scattering (DLS) and scanning electron microscopy (SEM) as spherical nanoparticles (NPs) of 170 ± 4 nm hydrodynamic diameter, 30 ± 2 mV of zeta-potential and 0.11 ± 0.01 of polydispersity. Mice immunization with the NPs elicited high OVA-specific IgG1 and low OVA-specific IgG2a production, indicating a Th-2 response. Delayed-type hypersensitivity reaction (DTH) was low and comparable to the one elicited by Al(OH) 3 /OVA, suggesting again a Th-2 response. PDDA advantages as an adjuvant were simplicity (a single-component adjuvant), low concentration needed (0.01 mg·mL −1 PDDA) combined with antigen yielding neglectable cytotoxicity, and high stability of PDDA/OVA dispersions. The NPs elicited much higher OVA-specific antibodies production than Al(OH) 3 /OVA. In vivo, the nano-metric size possibly assured antigen presentation by antigen-presenting cells (APC) at the lymph nodes, in contrast to the location of Al(OH) 3 /OVA microparticles at the site of injection for longer periods with stimulation of local dendritic cells. In the future, it will be interesting to evaluate combinations of the antigen with NPs carrying both PDDA and elicitors of the Th-1 response.Vaccines 2020, 8, 105 2 of 16 or cationic polymers on superparamagnetic iron oxide NPs [18] have also been proposed as effective micro or nanomaterials able to effectively interact with antigens and antigen-presenting cells (APC).Major mechanisms for taking up the cationic assemblies depend on size [19,20]. Nanoparticles with 20-200 nm mean diameter are like viruses and usually taken up by endocytosis via clathrin-coated vesicles, caveolae, or their independent receptors, and preferentially ingested by dendritic cells (DC) [21]. Microparticles with 500-5000 nm diameter are like bacteria, captured by phagocytosis and primarily ingested by macrophages. All particles used in vaccine formulations are consequently internalized efficiently by APC by one or a combination of the quoted mechanisms [22,23]. Particles with diameters smaller than 500 nm, in particular the nano-sized ones with 40-100 nm diameter, are more efficient to promote CD8 and CD4 type 1 T-helper cells responses than those with diameters above 500 nm; large particles, more similar to Al (OH) 3 , usually induce good T-helper cells type 2 improvement in antibody responses [22]. In summary, cationic micro and nanoparticles are effectively taken up both by macrophages and dendritic cells since electrostatic attraction promotes particle binding and subsequent internalization [11,14,20,24,25]. Cationic particles and liposomes containing dioctadecyldimethylammonium bromide (DODAB) cationic lipid [13,26] carrying Mycobacterium tuberculosis [13,27], Chlamydia trachomatis [11], or Neisseria meningitides antigens enhanced the cellular and humoral immune re...

Biocompatible lipid polymer nanoparticles (NPs) previously used as antimicrobial agents are explored here as immuno-adjuvants. Poly (methyl methacrylate) (PMMA)/dioctadecyldimethylammonium bromide (DODAB)/poly (diallyldimethylammonium chloride) (PDDA) nanoparticles (NPs) were prepared by emulsion polymerization of methyl methacrylate (MMA) in the presence of DODAB and PDDA, with azobisisobutyronitrile (AIBN) as the initiator. NPs characterization after dialysis by dynamic light-scattering yielded 225 ± 2 nm hydrodynamic diameter (Dz), 73 ± 1 mV zeta-potential (ζ), and 0.10 ± 0.01 polydispersity (P). Ovalbumin (OVA) adsorption reduced ζ to 45 ± 2 mV. Balb/c mice immunized with NPs/OVA produced enhanced OVA-specific IgG1 and IgG2a, exhibited moderate delayed type hypersensitivity reaction, and enhanced cytokines production (IL-4, IL-10, IL-2, IFN-γ) by cultured spleen cells. There was no cytotoxicity against cultured macrophages and fibroblasts. Advantages of the PMMA/DODAB/PDDA NPs were high biocompatibility, zeta-potential, colloidal stability, and antigen adsorption. Both humoral and cellular antigen-specific immune responses were obtained.

Subunit vaccines rely on adjuvants carrying one or a few molecular antigens from the pathogen in order to guarantee an improved immune response. However, to be effective, the vaccine formulation usually consists of several components: an antigen carrier, the antigen, a stimulator of cellular immunity such as a Toll-like Receptors (TLRs) ligand, and a stimulator of humoral response such as an inflammasome activator. Most antigens are negatively charged and combine well with oppositely charged adjuvants. This explains the paramount importance of studying a variety of cationic supramolecular assemblies aiming at the optimal activity in vivo associated with adjuvant simplicity, positive charge, nanometric size, and colloidal stability. In this review, we discuss the use of several antigen/adjuvant cationic combinations. The discussion involves antigen assembled to 1) cationic lipids, 2) cationic polymers, 3) cationic lipid/polymer nanostructures, and 4) cationic polymer/biocompatible polymer nanostructures. Some of these cationic assemblies revealed good yet poorly explored perspectives as general adjuvants for vaccine design.