The elution profile was consistent with native TMGMV and native or treated TMGMV particles eluted at ~8 mL from the Superose 6 column . As a complementary method, DLS was used to determine the hydrodynamic radius of TMGMV; DLS provides insight into the TMGMV formulation and its possible aggregation state, albeit an estimated measure given the high aspect ratio shape of TMGMV. DLS revealed signs of particle breakage when UV-TMGMV was treated with high doses of UV light . There was a trend that the average hydrodynamic radius of TMGMV decreased from 125 nm to 112, 102, 99, 91 and 78 nm with increasing UV doses of 0, 1, 5, 7.5, 10, and 15 J.cm-2 , respectively. DLS also revealed signs of particle aggregation in the βPL-TMGMV formulations ; compared to native TMGMV , βPL-TMGMV recorded hydrodynamic radii between 165 and 215 nm in samples treated with 0, 100, 500, 750, 1000, and 1500 mM βPL. In contrast, formalin treated TMGMV showed no signs of particle breakage nor aggregation with average lengths of 125 to 129 nm in samples treated with 0, 100, 250, 500, 750, and 1000 mM formalin .In TEM images, the polydispersity of TMGMV was previously reported218 and was attributed to the methods used to produce and purify TMGMV, as well as to prepare the TEM grid samples – during the drying process the particles are likely to break . TEM data concurred with the observations made by DLS. While the native TMGMV averaged a size of 180 ± 76 nm, the UV-TMGMV revealed minor signs of breakage, and Form-TMGMV retain its structural integrity. βPL-TMGMV did not show sign of aggregation but rather formed head-to-tail self-assembling filament. This phenomenon was previously reported using TMV assisted by aniline polymerization, and was attributed to a combination of hydrophobic interactions, electrostatic forces between the dipolar ends of adjacent particles.We hypothesize that the acylation and alkylation of amino acid residues toward the opposite ends of TMGMV promotes such interactions. Next, we assessed the RNA state after UV, βPL, and formalin treatment.
TMGMV contains a positive-sense,nft hydroponic system single-stranded RNA genome of 6355 nucleotides and contains more than 400 sites of adjacent uracils prone to dimerization . Overall, UV-visible spectroscopy indicated that the RNA to protein ratio of βPLTMGMV and Form-TMGMV remained close to 1.2, indicating no degradation or loss of RNA – as expected . UV-TMGMV suffered from an increase in the 260:280 ratio from 1.2 to 1.3. We attribute this change to coat protein breakage, as was observed in the gel electrophoresis experiments . SDS-PAGE gels were imaged following staining for proteins and nucleic acid under white light and UV light. While the coat proteins of TMGMV are ~17 kDa in size, a second protein band was observed in the UV-TMGMV treated samples, and its intensity increased with UV dosage. It should be noted that free coat protein was not detectable by SEC ; therefore, the smaller coat protein may be partially broken yet still be assembled in the nucleoprotein complex. We attempted to identify the amino acid sequence of the ~14 kDa and ~17 kDa bands by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry , however, we were unable to clearly resolve the bands and thus could not obtain pure samples for analysis. Denatured βPL-TMGMV coat proteins showed no sign of protein breakage or aggregation regardless of the dose of βPL used during the treatment. In contrast, the higher the dose of formalin, the more inter-CP crosslinking was observed, as indicated by the presence of an additional band with high molecular weight. GelRed staining of the RNA content of TMGMV particles, revealed no significant changes in RNA motility in βPL-TMGMV and form-TMGMV samples, but signs of RNA breakage in samples treated with UV doses above 1 J.cm-2 . The genome content of each formulation was further analyzed following RNA extraction from the TMGMV formulations on native agarose gels . We observed that treatment doses higher than 1 J.cm-2 of UV, or 10 mM of βPL and 100 mM formalin led to significant RNA damage and a decrease in total RNA recovery. Based on these biochemical data, we hypothesized that a minimum of 5 J.cm-2 of UV light, 100 mM βPL, and 500 mM of formalin would have been required to inactivate TMGMV; at these concentrations, the overall structural integrity of the particles was maintained, but RNA damage was visible.
Tn86, Samsun-NN, and TSA were seeded and maintained in a greenhouse and challenged with native or UV/chemically treated TMGMV when the plants were about 30 days old; fully developed new leaves were mechanically inoculated by gently abrading with a Q-tips swab dipped in native or inactivated TMGMV. Five plant replicates were inoculated for each treatment condition in addition to a negative control . Leaves were imaged and harvested individually ~20 days post-inoculation .In addition to visual inspection for symptoms, RT-PCR was carried out on the total RNA content extracted from individual leaves to further attest for the presence of TMGMV infection or lack thereof . A total of three leaves per treatment condition was selected randomly and analyzed by RT-PCR. This method is a more sensitive assay as opposed to visual inspection of the leaves; for example, visual inspection of the leaves may indicate a lack of apparent infection when using 5 J.cm-2 of UV, 500 mM βPL, or 500 mM formalin in either plant species tested . Yet, at these concentrations, the leaves were TMGMV positive in Tn86 and TSA. Agarose gel electrophoresis confirmed the inactivating UV dose was consistent amongst the 3 plant species tested . While 750 mM βPL was enough to inactivate TMGMV in Tn86 and Samsun-NN, 1500 mM was required to prevent TMGMV infection in the hypersensitive TSA. Therefore, one could inactivate TMGMV using 750 mM βPL and still use it as a bioherbicide with high specificity against TSA; which may be an interesting extension of the current formulation. Formalin was the least consistent treatment modality and required doses varying from 1000 mM, 250 mM, and 750 mM to inactivate Tn86, Samsun-NN, and TSA, respectively. Overall, the required treatment doses to prevent infection in all three plant species were 10 J.cm-2 UV, 1.5 M βPL 1 M formalin. However, given the variability of formalin dosage needed to achieve inactivation, this may be the least favorable to use for commercialization. All three treatment modalities have their own set of advantages and disadvantages to produce inactivated TMGMV for safe agricultural and environmental applications . UV treatment is the cheapest, fastest and most reproducible inactivation modality, but leads to shortening of the particles; 10 J.cm-2 UV-TMGMV particles are on average 30 nm shorter than native TMGMV .
In contrast, βPL maintains particle integrity, although it leads to end-to-end alignment of TMGMV; furthermore, βPL is an expensive and biohazardous chemical; the chemical treatment also requires additional purification steps therefore reducing yields by 40-60%. Similarly, formalin maintains particle integrity but requires a long treatment incubation ; the additional purification steps required to remove the treatment reagents are also at the cost of lower yields . Lastly, formalin treatment gave the least consistent inactivation results among different plant species, and therefore may require careful optimization for each species of interest. Altogether, UV inactivation may be the most suitable; it could be easily integrated into the purification process. As previously mentioned, the inactivation of TMGMV by UV light has been reported in the 20th century using the focal lesion quantification method.267,271 These studies reported using different sources of UV light with various intensities and power settings, which makes it difficult to compare the results. In addition, the time of UV exposure was recorded to assess UV inactivation instead of the more accurate J.cm-2 units of measure; for example, Ginoza et al. reported full inactivation of TMGMV after 2 min of UV exposure, while Streeter et al. stated that a 6 min exposure was required. Using our system, 2 min and 6 min of UV exposure would correspond to ~1 and ~2.5 J.cm-2 , respectively. At these concentrations, the leaves would appear symptomless but RT-PCR revealed the presence of infectious TMGMV . The plant virus cowpea mosaic virus has been shown to be inactivated at UV doses of 2.5 J.cm-2 . CPMV consists of a bipartite ssRNA virus forming a 31 nm icosahedron with pseudo T=3 symmetry. The differences in UV dose required to yield inactivated virus preparations can be explained by differences in virus structure and assembly: CPMV’s ssRNA genome is encapsulated into the internal cavity of the capsid; in contrast, TMGMV’s genome is incorporated into the nucleoprotein assembly – thus the TMGMV is somewhat buried in the coat protein structure, which likely confers enhanced stability. The reported inactivation of mammalian viruses such as Influenza HIV , Hepatitis A required lower doses,hydroponic nft system most likely due to a higher propensity for uracils in their genome to dimerize. βPL and formalin are more commonly used to produce non-virulent mammalian virus vaccines.Compared to plant viruses, many mammalian viruses have a lipid envelop that can be cross linked by formalin or acylated/alkylated by βPL; thus they generally require lower treatment doses to be inactivated. For example, the equine herpesvirus type I279, eastern equine encephalitis and poliomyelitis type II280, HIV281, and the influenza virus were successfully inactivated with 5-60 mM βPL. Hepatitis A , Japanese encephalitis virus , HIV281 , influenza A virus, and rabies were also successfully treated with 5-120 mM of formalin. It is the structural integrity of TMGMV that makes it attractive for exploitation in nanoengineering and environmental applications; however, these same features make it harder – yet not impossible – to generate inactivated TMGMV preparations, yet the dose requires vs. mammalian vaccine development is about 10x fold higher.
Nanoparticle carriers are used for targeting chemotherapies and immunotherapies to tumors to increase tissue specificity and effective payload delivery with reduced systemic adverse effects. Most nanoparticle-encapsulated cancer therapeutics are delivered to the tumor site by exploiting the local tumor environment consisting of the combination of leaky vasculature and deficient lymphatic clearance, i.e., enhanced permeability and retention . Some strategies also exploit the targeting of disease-specific molecular signatures, as yet no targeted nanoparticle has been translated into clinical treatment. If a target site can be identified, then the carrier diffusion and distribution of the delivered payload are critical to treatment success. Nanoparticles injected in the systemic circulation target either the vasculature or the periphery of the tumor. Limited nanoparticle-carrier diffusion can prevent drug accumulation to a lethal concentration in the tumor tissue and therefore promote cancer cell survival. Surviving cancer cells often become more aggressive and develop a drug resistance phenotype.Here, I develop the basis for quantitative analysis of nanoparticle diffusion and uptake in a solid tumor. Nanoparticle size and shape as well as surface chemistry determine the fate of the carrier and its efficacy. A growing body of data shows increased tumor homing and tissue penetration with elongated, rather than spherical, nanomaterials. Elongated, rod-shaped or filamentous nanoparticles have enhanced margination and increased transport across tissue membranes. Geng et al.demonstrated that virus-like filomicelles with higher aspect ratios than spherical particles deliver the chemotherapeutic drug paclitaxel to human-derived tumor xenografts in mice more effectively and with increased efficacy. Chauhan et al.compared the intratumoral diffusion of bio-stable colloidal quantum dots as nanorods and nanospheres with identical charge and surface coating. Nanorods penetrated tumors 4.1 times faster than nanospheres of the same hydrodynamic radius and occupied a tumor volume 1.7 times greater. Correspondingly, we found that filamentous potato virus X compared to spherical cowpea mosaic virus has enhanced tumor homing and tissue penetration, particularly in the core of the tumor.Contradictory results were obtained by Reuter et al., who compared sphere-like and rod-shaped nanogels using PRINT technology. They observed that smaller nanospheres had 5 fold greater tumor accumulation compared to higher aspect ratio nanorods. I hypothesize that this difference may be due to the different tumor model used. It has been previously shown that differences in tumor vasculature affect shape-dependent nanoparticle extravasation.In addition, other factors may have influenced the results, such as the differences in surface charge and aspect ratio . Therefore, there is a need to investigate the mechanics of diffusion and accumulation of high aspect ratio nanoparticles within the tumor microenvironment.