Background: Influenza virus is one of the major respiratory virus infections that is a global health concern. Although there are already approved vaccines, most are administered via the intramuscular route, which is usually painful, leading to vaccine hesitancy. To this end, exploring the non-invasive, transdermal vaccination route using dissolving microneedles would significantly improve vaccine compliance. Research on innovative vaccine delivery systems, such as antigen-loaded PLGA microparticles, has the potential to pave the way for a broader range of vaccine candidates. Methods: In this proof-of-concept study, a combination of the inactivated influenza A H1N1 virus and inactivated influenza A H3N2 virus were encapsulated in a biodegradable poly (lactic-co-glycolic acid) (PLGA) polymeric matrix within microparticles, which enhanced antigen presentation. The antigen PLGA microparticles were prepared separately using a double emulsion (w/o/w), lyophilized, and characterized. Next, the vaccine microparticles were assessed in vitro in dendritic cells (DC 2.4) for immunogenicity. To explore pain-free transdermal vaccination, the vaccine microparticles were loaded into dissolving microneedles and administered in mice (n = 5). Results: Our vaccination study demonstrated that the microneedle-based vaccine elicited strong humoral responses as demonstrated by high antigen-specific IgA, IgG, IgG1, and IgG2a antibodies in serum samples and IgA in lung supernatant. Further, the vaccine also elicited a strong cellular response as evidenced by high levels of CD4+ and CD8a+ T cells in lymphoid organs such as the lymph nodes and spleen. Conclusion: The delivery of influenza vaccine-loaded PLGA microparticles using microneedles would be beneficial to individuals experiencing needle-phobia, as well as the geriatric and pediatric population.

Vaccines remain one of the most powerful tools in modern medicine, having revolutionized public health by preventing millions of deaths and controlling the spread of infectious diseases worldwide. However, conventional needle-based vaccines face several limitations, including pain and discomfort, the need for cold-chain infrastructure, reliance on trained healthcare personnel, risk of cross-contamination, and limited accessibility in low-resource settings. These challenges have spurred the development of non-invasive vaccination approaches that promise safer, more accessible, and patient-friendly immunization. Non-invasive immunizations not only eliminate the need for needles but may also enhance compliance and enable mucosal immune responses. To harness the full potential of these innovative delivery routes, a comprehensive understanding of their formulation strategies and mechanism of action is essential. This review aims to comprehensively discuss recent advancements in oral, intranasal, microneedle, buccal, sublingual, and vaginal vaccinations and highlight their underlying immunological mechanisms, formulation strategies in preclinical studies, examples of marketed products, and ongoing clinical trials.

Background: In recent years, the COVID-19 pandemic has significantly impacted global health, largely driven by the emergence of various genetic mutations within the SARS-CoV-2 virus. Although the pandemic phase has passed, the full extent of the virus’s evolutionary trajectory remains uncertain, highlighting the need for continued research in vaccine development to establish a cross-reactive approach that can effectively address different variants. This proof-of-concept study aimed to assess the effectiveness of microparticulate vaccine delivery through the minimally invasive microneedle route of administration, using a heterologous prime–booster strategy against the SARS-CoV-2 virus. Method: This strategy uses the whole inactivated virus of the Delta variant for the prime dose and the whole inactivated virus of the Omicron variant for the booster dose, with alum as an adjuvant. The formulation of microparticles involves encapsulating the antigens in poly lactic-co-glycolic acid (PLGA) polymer, which provides sustained release and enhances immunogenicity while protecting the antigen. Microparticles were tested for in vitro assays, and characterization included particle size, zeta potential, and encapsulation efficacy. Furthermore, serum was collected post-administration of the vaccine in mice and was tested for antibody levels. Result: In vitro assays confirmed the non-cytotoxicity and the ability of microparticles to activate the immune response of the vaccine particles. Administering this microparticulate vaccine via microneedles has proven effective for delivering vaccines through the skin. We also observed significantly higher antigen-specific antibody levels and cross-reactivity in the strains. Conclusions: Our adjuvanted microparticulate-based heterologous prime–booster vaccine strategy showed cross-reactivity among the strains and was successfully delivered using microneedles.

Background: The neuropeptide oxytocin has been identified as a potential therapeutic molecule. However, the therapeutic potential of this molecule is limited due to the challenges faced in oxytocin delivery to the brain. Scientific innovation has led to the breakthrough discovery of many modalities to encapsulate molecules for targeted drug delivery, which can enhance oxytocin delivery to the brain. This research aimed to explore a microfluidics-based system that optimizes the formulation of cross-linked bovine serum albumin (BSA) nanoparticles encapsulating oxytocin. Methods: First, the formulation parameters were optimized using a design of experiments (DOE) by evaluating the effect of flow rate, polymer concentration, and the binary solvent mixture polarity on the nanoparticle size. Drug encapsulation efficiency, release, and kinetics profile were characterized. These oxytocin nanoparticles were conjugated to rabies virus glycoprotein (RVG), a brain-targeting ligand, and the conjugation efficiency was determined. Results: The sizes of the nanoparticles were between 50 nm and 75 nm with a 80%. Approximately 58% of oxytocin was released from the nanoparticles within the first six hours, showing an initial burst that is ideal for seizure control and thereafter exhibiting the Korsmeyer–Peppas release kinetics. Conclusions: For the first time, we demonstrated the microfluidics method of formulating nanoparticles with particle size of less than 100 nm, with improved encapsulation efficiency and optimal release profile for oxytocin brain delivery.

Background/Objectives: Cervical dysplasia, a precursor to cervical cancer, represents a significant global health challenge, particularly in regions like Central America, Africa, and Southeast Asia. Current management approaches rely on surgical or ablative interventions, which can lead to complications, for example, preterm birth and cervical insufficiency. Therefore, developing non-invasive, localized therapeutic alternatives is of great clinical interest. Curcumin is a natural compound that suppresses the progression of cervical cancer, but it has poor oral bioavailability and high clearance. Methods: We incorporated curcumin into solid lipid nanoparticles, which were then loaded into rapidly dissolving films. These films show the sustained release profile of curcumin at the localized vaginal site, demonstrating release kinetics consistent with the Korsmeyer–Peppas model. Results: The curcumin solid lipid nanoparticles yielded a size of 341 nm and a polydispersity index of 0.373, and the zeta potential was −23.4 mV. The encapsulation efficiency of curcumin solid lipid nanoparticles was 77.27% using a validated HPLC method. FTIR analysis supported successful incorporation of curcumin into the lipid matrix. A Box–Behnken Design of Experiments optimized the key film formulation parameters and yielded a film with a tensile strength of 2.8 mPa, disintegration time of 3 min, folding endurance of 263, film thickness of 0.426 mm and a pH of 4.0. Conclusions: In vitro assays in human cervical carcinoma cells demonstrated enhanced mortality and autophagosome formation by the curcumin solid lipid nanoparticles when compared to free curcumin. Surface expression of MHC I, MHCII, CD40 and CD80 in peripheral dendritic cells was significantly higher in the curcumin solid lipid nanoparticles than in free curcumin. Results show that solid lipid nanoparticles loaded with curcumin effectively stimulate and activate dendritic cells, supporting immune cell activation outside the tumor microenvironment. The proposed pain-free self-administration strategies will lead to increased patient compliance.

Background: In response to the emergence of immune-evasive variants of SARS-CoV-2, this study explores a novel heterologous vaccination strategy using a microparticulate formulation approach that is delivered via oral dissolving film (ODF) formulations into the buccal cavity. Heterologous administration has the potential to generate cross-reactive antibodies, which can be especially beneficial against viruses with ever-mutating variants. Moreover, the microparticulate oral dissolving film-based vaccine approach is a non-invasive vaccine delivery platform. Methods: The vaccine design incorporated whole inactivated Delta and Omicron variants of the virus, administered at prime and booster doses, respectively, effectively encapsulated in a Poly(lactic-co-glycolic) acid (PLGA) polymer matrix, and adjuvanted with Alum to enhance immune activation. Following vaccination, serum, mucosal, and tissue samples were analyzed to evaluate humoral and cellular immune responses against the model antigen, as well as other variants such as Alpha and Beta variants, to understand the cross-reactive response. Result: In vitro evaluations confirmed the vaccine’s safety and its ability to stimulate immune responses. On administering microparticulate oral dissolving films to mice, whole inactivated delta and omicron variant-specific antibodies were observed in serum samples along with neutralizing titers in terminal week. The formulated vaccine showed significant secretory IgA antibody levels in mucosal samples. Moreover, CD4⁺ and CD8a cellular responses were observed in tissue samples of spleen and lymph nodes, along with antibodies (IgG, IgA, and IgM) detected in lung supernatant samples. Humoral and cellular cross-reactive antibodies were observed in the samples. Conclusions: This approach offers a promising platform for developing next-generation vaccines capable of inducing broad immunity.