Design of nanoparticle-based dry powder pulmonary vaccines

Bioinspired Multiscale Mineralization: From Fundamentals to Potential Applications

The wondrous and imaginative designs of nature have always been an inexhaustible treasure trove for material scientists. Throughout the long evolutionary process, biominerals with hierarchical structures possess some specific advantages such as outstanding mechanical properties, biological functions, and sensing performances, the formation of which (biomineralization) is delicately regulated by organic component. Provoked by the subtle structures and profound principles of nature, bioinspired functional minerals can be designed with the participation of organic molecules. Because of the designable morphology and functions, multiscale mineralization has attracted more and more attention in the areas of medicine, chemistry, biology, and material science. This review provides a summary of current advancements in this extending topic. The mechanisms underlying mineralization is first concisely elucidated. Next, several types of minerals are categorized according to their structural characteristic, as well as the different potential applications of these materials. At last, a comprehensive overview of future developments for bioinspired multiscale mineralization is given. Concentrating on the mechanism of fabrication and broad application prospects of multiscale mineralization, the hope is to provide inspirations for the design of other functional materials.

Inhaled SARS-CoV-2 vaccine for single-dose dry powder aerosol immunization

The COVID-19 pandemic has fostered major advances in vaccination technologies1-4; however, there are urgent needs for vaccines that induce mucosal immune responses and for single-dose, non-invasive administration4-6. Here we develop an inhalable, single-dose, dry powder aerosol SARS-CoV-2 vaccine that induces potent systemic and mucosal immune responses. The vaccine encapsulates assembled nanoparticles comprising proteinaceous cholera toxin B subunits displaying the SARS-CoV-2 RBD antigen within microcapsules of optimal aerodynamic size, and this unique nano-micro coupled structure supports efficient alveoli delivery, sustained antigen release and antigen-presenting cell uptake, which are favourable features for the induction of immune responses. Moreover, this vaccine induces strong production of IgG and IgA, as well as a local T cell response, collectively conferring effective protection against SARS-CoV-2 in mice, hamsters and nonhuman primates. Finally, we also demonstrate a mosaic iteration of the vaccine that co-displays ancestral and Omicron antigens, extending the breadth of antibody response against co-circulating strains and transmission of the Omicron variant. These findings support the use of this inhaled vaccine as a promising multivalent platform for fighting COVID-19 and other respiratory infectious diseases.

Aerosol pulmonary immune engineering

Aerosolization of immunotherapies poses incredible potential for manipulating the local mucosal-specific microenvironment, engaging specialized pulmonary cellular defenders, and accessing mucosal associated lymphoid tissue to redirect systemic adaptive and memory responses. In this review, we breakdown key inhalable immunoengineering strategies for chronic, genetic, and infection-based inflammatory pulmonary disorders, encompassing the historic use of immunomodulatory agents, the transition to biological inspired or derived treatments, and novel approaches of complexing these materials into drug delivery vehicles for enhanced release outcomes. Alongside a brief description of key immune targets, fundamentals of aerosol drug delivery, and preclinical pulmonary models for immune response, we survey recent advances of inhaled immunotherapy platforms, ranging from small molecules and biologics to particulates and cell therapies, as well as prophylactic vaccines. In each section, we address the formulation design constraints for aerosol delivery as well as advantages for each platform in driving desirable immune modifications. Finally, prospects of clinical translation and outlook for inhaled immune engineering are discussed.

Aluminum-based metal-organic framework nanoparticles as pulmonary vaccine adjuvants

The adoption of pulmonary vaccines to advantageously provide superior local mucosal protection against aerosolized pathogens has been faced with numerous logistical and practical challenges. One of these persistent challenges is the lack of effective vaccine adjuvants that could be well tolerated through the inhaled route of administration. Despite its widespread use as a vaccine adjuvant, aluminum salts (alum) are not well tolerated in the lung. To address this issue, we evaluated the use of porous aluminum (Al)-based metal-organic framework (MOF) nanoparticles (NPs) as inhalable adjuvants. We evaluate a suite of Al-based MOF NPs alongside alum including DUT-4, DUT-5, MIL-53 (Al), and MIL-101-NH₂ (Al). As synthesized, MOF NPs ranged between ~ 200 nm and 1 µm in diameter, with the larger diameter MOFs matching those of commercial alum. In vitro examination of co-stimulatory markers revealed that the Al-based MOF NPs activated antigen presenting cells more effectively than alum. Similar results were found during in vivo immunizations utilizing ovalbumin (OVA) as a model antigen, resulting in robust mucosal humoral responses for all Al MOFs tested. In particular, DUT-5 was able to elicit mucosal OVA-specific IgA antibodies that were significantly higher than the other MOFs or alum dosed at the same NP mass. DUT-5 also was uniquely able to generate detectable IgG2a titers, indicative of a cellular immune response and also had superior performance relative to alum at equivalent Al dosed in a reduced dosage vaccination study. All MOF NPs tested were generally well-tolerated in the lung, with only acute levels of cellular infiltrates detected and no Al accumulation; Al content was largely cleared from the lung and other organs at 28 days despite the two-dose regime. Furthermore, all MOF NPs exhibited mass median aerodynamic diameters (MMADs) of ~ 1.5-2.5 µm when dispersed from a generic dry powder inhaler, ideal for efficient lung deposition. While further work is needed, these results demonstrate the great potential for use of Al-based MOFs for pulmonary vaccination as novel inhalable adjuvants.

Polymeric Nanoparticles for Inhaled Vaccines

Many recent studies focus on the pulmonary delivery of vaccines as it is needle-free, safe, and effective. Inhaled vaccines enhance systemic and mucosal immunization but still faces many limitations that can be resolved using polymeric nanoparticles (PNPs). This review focuses on the use of properties of PNPs, specifically chitosan and PLGA to be used in the delivery of vaccines by inhalation. It also aims to highlight that PNPs have adjuvant properties by themselves that induce cellular and humeral immunogenicity. Further, different factors influence the behavior of PNP in vivo such as size, morphology, and charge are discussed. Finally, some of the primary challenges facing PNPs are reviewed including formulation instability, reproducibility, device-related factors, patient-related factors, and industrial-level scale-up. Herein, the most important variables of PNPs that shall be defined in any PNPs to be used for pulmonary delivery are defined. Further, this study focuses on the most popular polymers used for this purpose.

Gold Nanorods for Drug and Gene Delivery: An Overview of Recent Advancements

Over the past few decades, gold nanomaterials have shown great promise in the field of nanotechnology, especially in medical and biological applications. They have become the most used nanomaterials in those fields due to their several advantageous. However, rod-shaped gold nanoparticles, or gold nanorods (GNRs), have some more unique physical, optical, and chemical properties, making them proper candidates for biomedical applications including drug/gene delivery, photothermal/photodynamic therapy, and theranostics. Most of their therapeutic applications are based on their ability for tunable heat generation upon exposure to near-infrared (NIR) radiation, which is helpful in both NIR-responsive cargo delivery and photothermal/photodynamic therapies. In this review, a comprehensive insight into the properties, synthesis methods and toxicity of gold nanorods are overviewed first. For the main body of the review, the therapeutic applications of GNRs are provided in four main sections: (i) drug delivery, (ii) gene delivery, (iii) photothermal/photodynamic therapy, and (iv) theranostics applications. Finally, the challenges and future perspectives of their therapeutic application are discussed.

Future of nanomedicines for treating respiratory diseases

INTRODUCTION

Nanoparticles are under discussion in drug delivery for more than 20 years now, but examples for nanoparticulate formulations in the treatment of respiratory diseases are rare and mostly limited to the administration of sub-micron drug particles (ultrafine particles). However, nanoparticles may also carry specific benefits for respiratory treatment. Are nanoparticles the next-generation drug carrier system to facilitate systemic delivery, sustained release and cancer treatment in the lungs?

AREAS COVERED

This review will look into the promises and opportunities of the use of nanoparticles in the treatment of respiratory diseases. Important aspects to discuss are the fate of nanoparticles in the lung and mechanisms for reproducible delivery of nanoparticulate formulations to the lungs. Examples are given where nanoparticles may be advantageous over for traditional formulations and further aspects to explore are mentioned.

EXPERT OPINION

The benefit of nanoparticulate systems for respiratory delivery adds to the portfolio of possible formulation strategies, depends on the intended functionality and needs more exploration. Advantages of such systems are only seen in special cases.

Nanoparticle surface charge impacts distribution, uptake and lymph node trafficking by pulmonary antigen-presenting cells

Engineered nanoparticles have the potential to expand the breadth of pulmonary therapeutics, especially as respiratory vaccines. Notably, cationic nanoparticles have been demonstrated to produce superior local immune responses following pulmonary delivery; however, the cellular mechanisms of this increased response remain unknown. To this end, we investigated the cellular response of lung APCs following pulmonary instillation of anionic and cationic charged nanoparticles. While nanoparticles of both surface charges were capable of trafficking to the draining lymph node and were readily internalized by alveolar macrophages, both CD11b and CD103 lung dendritic cell (DC) subtypes preferentially associated with cationic nanoparticles. Instillation of cationic nanoparticles resulted in the upregulation of Ccl2 and Cxc10, which likely contributes to the recruitment of CD11b DCs to the lung. In total, these cellular mechanisms explain the increased efficacy of cationic formulations as a pulmonary vaccine carrier and provide critical benchmarks in the design of pulmonary vaccine nanoparticles.

FROM THE CLINICAL EDITOR

Advance in nanotechnology has allowed the production of precise nanoparticles as vaccines. In this regard, pulmonary delivery has the most potential. In this article, the authors investigated the interaction of nanoparticles with various types of lung antigen presenting cells in an attempt to understand the cellular mechanisms. The findings would further help the future design of much improved vaccines for clinical use.

Inhaled drug treatment for tuberculosis: Past progress and future prospects

Since the 1990s the rising incidence of multiple drug resistant TB, particularly in the context of human immunodeficiency virus co-infected patients, has threatened global TB control. At that time funding agencies began to support formal investigation of aerosol therapy which until then had been the subject of case reports of individual investigators. Over the last decade, proponents of aerosol therapy have increased in number within the TB research community as the incidence of multiple and extremely drug resistant TB has increased dramatically around the world. Aerosol therapy offers the potential to deliver drug at target concentrations directly into the lungs, use the alveolar-capillary interface to achieve systemic levels, while reducing the risk of systemic toxicity seen with parentally administered doses. In addition, there are insufficient new drugs in the pipeline to anticipate the appearance of a new regimen in time to assure future control of drug resistance. Consequently, alternative strategies are critical to achieving global TB control, and inhaled therapies should be considered as one such strategy.

Spray-Dried Multiscale Nano-biocomposites Containing Living Cells

Three-dimensional encapsulation of cells within nanostructured silica gels or matrices enables applications as diverse as biosensors, microbial fuel cells, artificial organs, and vaccines; it also allows the study of individual cell behaviors. Recent progress has improved the performance and flexibility of cellular encapsulation, yet there remains a need for robust scalable processes. Here, we report a spray-drying process enabling the large-scale production of functional nano-biocomposites (NBCs) containing living cells within ordered 3D lipid-silica nanostructures. The spray-drying process is demonstrated to work with multiple cell types and results in dry powders exhibiting a unique combination of properties including highly ordered 3D nanostructure, extended lipid fluidity, tunable macromorphologies and aerodynamic diameters, and unexpectedly high physical strength. Nanoindentation of the encasing nanostructure revealed a Young's modulus and hardness of 13 and 1.4 GPa, respectively. We hypothesized this high strength would prevent cell growth and force bacteria into viable but not culturable (VBNC) states. In concordance with the VBNC state, cellular ATP levels remained elevated even over eight months. However, their ability to undergo resuscitation and enter growth phase greatly decreased with time in the VBNC state. A quantitative method of determining resuscitation frequencies was developed and showed that, after 36 weeks in a NBC-induced VBNC, less than 1 in 10,000 cells underwent resuscitation. The NBC platform production of large quantities of VBNC cells is of interest for research in bacterial persistence and screening of drugs targeting such cells. NBCs may also enable long-term preservation of living cells for applications in cell-based sensing and the packaging and delivery of live-cell vaccines.

Distribution and Cellular Uptake of PEGylated Polymeric Particles in the Lung Towards Cell-Specific Targeted Delivery

PURPOSE

We evaluated the role of a poly(ethylene glycol) (PEG) surface coating to increase residence times and alter the cellular fate of nano- and microparticles delivered to the lung.

METHODS

Three sizes of PRINT hydrogel particles (80 × 320 nm, 1.5 and 6 μm donuts) with and without a surface PEG coating were instilled in the airways of C57/b6 mice. At time points of 1, 7, and 28 days, BALF and whole lungs were evaluated for the inflammatory cytokine Il-6 and chemokine MIP-2, histopathology, cellular populations of macrophages, dendritic cells (DCs), and granulocytes, and particulate uptake within these cells through flow cytometry, ELISAs, and fluorescent imaging.

RESULTS

Particles of all sizes and surface chemistries were readily observed in the lung with minimal inflammatory response at all time points. Surface modification with PEGylation was found to significantly increase lung residence times and homogeneous lung distribution, delaying macrophage clearance of all sizes, with the largest increase in residence time observed for 80 × 320 nm particles. Additionally, it was observed that DCs were recruited to the airway following administration of unPEGylated particles and preferentially associated with these particles.

CONCLUSIONS

Pulmonary drug delivery vehicles designed with a PEG surface coating can be used to delay particle uptake and promote cell-specific targeting of therapeutics.

Spray-Dried Influenza Antigen with Trehalose and Leucine Produces an Aerosolizable Powder Vaccine Formulation that Induces Strong Systemic and Mucosal Immunity after Pulmonary Administration

BACKGROUND

Pulmonary immunization has recently gained increased interest as a means to induce both systemic and mucosal immunity while eliminating issues associated with the use of needles in parenteral vaccination. However, in contrast to the inhaled delivery of small molecule drugs, a dry powder carrier platform that is readily adaptable to the incorporation of biomacromolecules (e.g., vaccine antigens) as a common standard is lacking. Spray-dried trehalose with leucine has previously been characterized and demonstrated to produce highly aerosolizable powders containing an amorphous glassy matrix suitable for stabilization of biomacromolecules. This study aimed to further extend the understanding in the use of this formulation as a dry powder carrier platform in an in vivo setting, using influenza antigen as a model, for pulmonary delivery of biomacromolecules.

METHODS

Spray-dried influenza vaccine was produced using previously established spray-drying conditions. The formulations were characterized to examine the impact of influenza antigen on the solid-state properties of the spray-dried powders. The optimal vaccine formulation was then selected for in vivo immunogenicity study in rats to evaluate the efficacy of the reconstituted spray-dried vaccine compared to liquid vaccine administered via pulmonary and subcutaneous routes.

RESULTS

The formation of amorphous glassy matrix and morphology of the spray-dried particles, within the protein concentration range used in the study, was not affected by the incorporation of the influenza antigen. However, the amount of proteins incorporated increased water content and reduced the glass transition temperature (Tg) of the formulation. Nevertheless, the spray-dried vaccine induced strong mucosal and systemic immunity comparable to liquid vaccine after pulmonary and subcutaneous immunization without causing any inflammation to the lung parenchyma.

CONCLUSIONS

The study demonstrated the usability of the spray-dried carrier as a promising platform for pulmonary delivery of influenza vaccine. The potential utility of this delivery system for other biomacromolecules may also be further explored.

Controlled analysis of nanoparticle charge on mucosal and systemic antibody responses following pulmonary immunization

Pulmonary immunization enhances local humoral and cell-mediated mucosal protection, which are critical for vaccination against lung-specific pathogens such as influenza or tuberculosis. A variety of nanoparticle (NP) formulations have been tested preclinically for pulmonary vaccine development, yet the role of NP surface charge on downstream immune responses remains poorly understood. We used the Particle Replication in Non-Wetting Templates (PRINT) process to synthesize hydrogel NPs that varied only in surface charge and otherwise maintained constant size, shape, and antigen loading. Pulmonary immunization with ovalbumin (OVA)-conjugated cationic NPs led to enhanced systemic and lung antibody titers compared with anionic NPs. Increased antibody production correlated with robust germinal center B-cell expansion and increased activated CD4(+) T-cell populations in lung draining lymph nodes. Ex vivo treatment of dendritic cells (DCs) with OVA-conjugated cationic NPs induced robust antigen-specific T-cell proliferation with ∼ 100-fold more potency than soluble OVA alone. Enhanced T-cell expansion correlated with increased expression of surface MHCII, T-cell coactivating receptors, and key cytokines/chemokine expression by DCs treated with cationic NPs, which were not observed with anionic NPs or soluble OVA. Together, these studies highlight the importance of NP surface charge when designing pulmonary vaccines, and our findings support the notion that cationic NP platforms engender potent humoral and mucosal immune responses.

Fate of TLR-1/TLR-2 agonist functionalised pDNA nanoparticles upon deposition at the human bronchial epithelium in vitro

BACKGROUND

Plasmid DNA vaccination is a promising approach, but studies in non-human primates and humans failed to achieve protective immunity. To optimise this technology further with focus on pulmonary administration, we developed and evaluated an adjuvant-equipped DNA carrier system based on the biopolymer chitosan. In more detail, the uptake and accompanying immune response of adjuvant Pam3Cys (Toll-like receptor-1/2 agonist) decorated chitosan DNA nanoparticles (NP) were explored by using a three-dimensional (3D) cell culture model of the human epithelial barrier. Pam3Cys functionalised and non-functionalised chitosan DNA NP were sprayed by a microsprayer onto the surface of 3D cell cultures and uptake of NP by epithelial and immune cells (blood monocyte-derived dendritic cells (MDDC) and macrophages (MDM)) was visualised by confocal laser scanning microscopy. In addition, immune activation by TLR pathway was monitored by analysis of interleukin-8 and tumor necrosis factor-α secretions (ELISA).

RESULTS

At first, a high uptake rate into antigen-presenting cells (MDDC: 16-17%; MDM: 68-75%) was obtained. Although no significant difference in uptake patterns was observed for Pam3Cys adjuvant functionalised and non-functionalised DNA NP, ELISA of interleukin-8 and tumor necrosis factor-α demonstrated clearly that Pam3Cys functionalisation elicited an overall higher immune response with the ranking of Pam3Cys chitosan DNA NP>chitosan DNA NP=DNA unloaded chitosan NP>control (culture medium).

CONCLUSIONS

Chitosan-based DNA delivery enables uptake into abluminal MDDC, which are the most immune competent cells in the human lung for the induction of antigen-specific immunity. In addition, Pam3Cys adjuvant functionalisation of chitosan DNA NP enhances significantly an environment favoring recruitment of immune cells together with a Th1 associated (cellular) immune response due to elevated IL-8 and TNF-α levels. The latter renders this DNA delivery approach attractive for potential DNA vaccination against intracellular pathogens in the lung (e.g., Mycobacterium tuberculosis or influenza virus).

Nanocarriers targeting dendritic cells for pulmonary vaccine delivery

Pulmonary vaccine delivery has gained significant attention as an alternate route for vaccination without the use of needles. Immunization through the pulmonary route induces both mucosal and systemic immunity, and the delivery of antigens in a dry powder state can overcome some challenges such as cold-chain and availability of medical personnel compared to traditional liquid-based vaccines. Antigens formulated as nanoparticles (NPs) reach the respiratory airways of the lungs providing greater chance of uptake by relevant immune cells. In addition, effective targeting of antigens to the most 'professional' antigen presenting cells (APCs), the dendritic cells (DCs) yields an enhanced immune response and the use of an adjuvant further augments the generated immune response thus requiring less antigen/dosage to achieve vaccination. This review discusses the pulmonary delivery of vaccines, methods of preparing NPs for antigen delivery and targeting, the importance of targeting DCs and different techniques involved in formulating dry powders suitable for inhalation.

Engineered PLGA nano- and micro-carriers for pulmonary delivery: challenges and promises

Objectives

The aim of this review is to summarize the current state-of-the-art in poly(lactic-co-glycolic acid) (PLGA) carriers for inhalation. It presents the rational of use, the potential and the recent advances in developing PLGA microparticles and nanoparticles for pulmonary delivery. The most promising particle engineering strategies are discussed, highlighting the advantages along with the major challenges for researchers working in this field.

Key findings

Biodegradable polymer carriers, such as PLGA particles, may permit effective protection and long-term delivery of the inhaled drug and, when adequately engineered, its efficient transport to the target. The carrier can be designed for inhalation on the basis of several strategies through the adequate combination of available particle technologies and excipients. In so doing, the properties of PLGA particles can be finely tuned at micro-size and nano-size level to fulfill specific therapeutic needs. This means not only to realize optimal in vitro/in vivo lung deposition of the formulation, which is still crucial, but also to control the fate of the drug in the lung after particle landing.

Summary

Although many challenges still exist, PLGA carriers may be highly beneficial and present a new scenario for patients suffering from chronic lung diseases and for pharmaceutical companies working to develop novel inhaled products.

Engineered nanostructural materials for application in cancer biology and medicine

Nanotechnology covers a wide variety of fields of research, including chemistry, physics, biology and medicine, with extensive applications in cancer, ranging from accurate, early detection of malignant lesions to minimizing metastasis. Continued development of cancer-targeted therapy has promising advantages: maximizing the effectiveness of anticancer drugs while decreasing the harmful systemic effects; tumor destruction via heating that takes advantage of magnetic nanoparticles' size, magnetization and biocompatibility; novel drug-delivery systems; and gene therapy functions to facilitate controlled drug loading and release inside the cytoplasm. These and other nanotechnology applications can contribute essential new knowledge in the fight against cancer.

Pulmonary immunization of guinea pigs with diphtheria CRM-197 antigen as nanoparticle aggregate dry powders enhance local and systemic immune responses

This study establishes the immune response elicited in guinea pigs after pulmonary and parenteral immunizations with diphtheria CRM-197 antigen (CrmAg). Several spray-dried powders of formalin-treated/untreated CrmAg nanoaggregates with L-leucine were delivered to the lungs of guinea pigs. A control group consisting of alum with adsorbed CrmAg in saline was administered by intramuscular injection. Animals received three doses of powder vaccines containing 20 or 40 μg of CrmAg. The serum IgG titers were measured for 16 weeks after the initial immunization; IgA titers were measured at the time of sacrifice in the broncho-alveolar lavage fluid. Further, toxin neutralization tests in naïve guinea pigs were performed for a few select serum samples. Histopathology of the lung tissues was conducted to evaluate inflammation or injury to the lung tissues. While the highest titer of serum IgG antibody was observed in guinea pigs immunized by the intramuscular route, those animals immunized with dry powder formulation by the pulmonary route, and without the adjuvant alum, exhibited high IgA titers. A pulmonary administered dry powder, compared to parenteral immunization, conferred complete protection in the toxin neutralization test. Mild inflammation was observed in lung tissues of animals receiving dry powder vaccines by the pulmonary route. Thus, administering novel CrmAg as dry powders to the lungs may be able to overcome some of the disadvantages observed with the existing diphtheria vaccine which is administered by the parenteral route. In addition, these powders will have the advantage of eliciting a high mucosal immune response in the lungs without using traditional adjuvants.

Immunization of guinea pigs with novel hepatitis B antigen as nanoparticle aggregate powders administered by the pulmonary route

Novel nanoparticle-aggregate formulations containing recombinant hepatitis B surface antigen (rHBsAg) were administered to the lungs of guinea pigs and antibodies generated to this antigen evaluated. Preparations of dry powders of: (a) rHBsAg encapsulated within poly(lactic-co-glycolic acid) (PLGA)/polyethylene glycol (PEG) nanoparticles (antigen nanoparticles, AgN(SD)), (b) rHBsAg in a physical mixture with blank PLGA/PEG nanoparticles (antigen nanoparticle admixture (AgNA(SD)), and (c) rHBsAg encapsulated in PLGA/PEG nanoparticles plus free rHBsAg (antigen nanoparticles and free antigen), were generated by spray drying with leucine. Control groups consisted of alum with adsorbed rHBsAg (AlumAg); reconstituted suspensions of spray-dried rHBsAg-loaded PLGA/PEG nanoparticles with leucine; and rHBsAg-loaded PLGA/PEG nanoparticles (AgN). Control preparations were administered by intramuscular injection; AgN was also spray instilled into the lungs. The IgG titers were measured in the serum for 24 weeks after the initial immunization; IgA titers were measured in the bronchio-alveolar lavage fluid. While the highest titer of serum IgG antibody was observed in guinea pigs immunized with AlumAg administered by the IM route, animals immunized with powder formulations via the pulmonary route exhibited high IgA titers. In addition, guinea pigs immunized with AgNA(SD) via the pulmonary route exhibited IgG titers above 1,000 mIU/ml in the serum (IgG titers above 10 mIU/ml is considered protective). Thus, the disadvantages observed with the existing hepatitis B vaccine administered by the parenteral route may be overcome by administering them as novel dry powders to the lungs. In addition, these powders have the advantage of eliciting a high mucosal immune response in the lungs without traditional adjuvants.

Gold nanoparticles: From nanomedicine to nanosensing

Because of their photo-optical distinctiveness and biocompatibility, gold nanoparticles (AuNPs) have proven to be powerful tools in various nanomedicinal and nanomedical applications. In this review article, we discuss recent advances in the application of AuNPs in diagnostic imaging, biosensing and binary cancer therapeutic techniques. We also provide an eclectic collection of AuNPs delivery strategies, including assorted classes of delivery vehicles, which are showing great promise in specific targeting of AuNPs to diseased tissues. However, successful clinical implementations of the promised applications of AuNPs are still hampered by many barriers. In particular, more still needs to be done regarding our understanding of the pharmacokinetics and toxicological profiles of AuNPs and AuNPs-conjugates.