Juan Pablo Giraldo

Optical sensors are powerful tools to monitor biological systems. However, their practical deployment is often limited by environmental interferences such as autofluorescence, mechanical motion, and fluctuating illumination. These challenges are particularly pronounced in plants because they require and use light, which has impaired the use of (fluorescent) sensors for plant stress signals such as H ₂ O ₂ . Here, we present a ratiometric sensing platform that overcomes these limitations by integrating three spectrally distinct components: 1) an H ₂ O ₂ sensor based on aptamer modified near infrared (NIR) fluorescent single walled carbon nanotubes (SWCNTs, ∼1000 nm), 2) a stable NIR reference based on polyethyleneglycol modified Egyptian Blue nanosheets (EB–NS, 900–955 nm) and 3) a visible (VIS) signal (∼641 nm) to correct for the NIR autofluorescence tail of plants (>835 nm). This ratiometric approach enables robust signal correction under relevant perturbations, including leaf rotation and wind‐induced motion. Furthermore, it allows continuous H ₂ O ₂ monitoring under dynamically varying illumination conditions (>300%), resulting in a 75% enhancement in signal contrast compared to single‐channel detection. By spectrally resolving nanosensor signals and endogenous plant autofluorescence, this strategy enables in vivo monitoring of stress‐induced H ₂ O ₂ under realistic environmental conditions. It establishes interference‐resistant optical sensing and advances field‐deployable nanosensor technologies for precision agriculture.

A lack of understanding of the properties that determine nanomaterial-plant cell wall interactions limits the advancement of nanoenabled agriculture. Herein, we integrated experimental and computational approaches to elucidate the role of nanoparticle size and Ca²⁺ cross-linking on the interactions between model plant cell walls composed of pectin and branched polyethylenimine-coated (bPEI) gold nanoparticles (AuNP 6.1, 36.1, and 75.5 nm). Quartz crystal microbalance with dissipation monitoring (QCM-D) and X-ray photoelectron spectroscopy (XPS) analyses demonstrated a size and Ca²⁺-induced cross-linking dependence during the attachment to and passive penetration into model cell walls due to pore size. In the absence of electrolytes, AuNP penetration into the pectin layer occurred with simultaneous expulsion of water for all particle sizes. In the presence of Ca²⁺, pectin cross-linking reduced porosity and blocked penetration of the 75.5 nm AuNPs while unexpectedly increasing the uptake of 6.1 and 36.1 nm AuNPs. Computational simulations showed a reduction in pectin pore size due to Ca²⁺-induced cross-linking that resulted in a high free energy cost of pore expansion. In the presence of Ca²⁺, significant overtone spreading was observed by QCM-D for the 6.1 and 36.1 nm AuNPs that was not observed without electrolytes, indicating that the smaller particles still penetrated through the cross-linked pectin layer, but the process was slower. Upon replacing Ca²⁺ with Mg²⁺, the pectin film was permeable to all three sizes of AuNPs, and less overtone spreading was observed, indicating that cross-linking effects are exclusive to Ca²⁺. Interestingly, a size-dependent induction time not reported before was observed for AuNP attachment to pectin model surfaces. This study elucidated size- and Ca²⁺ cross-linking-dependent physicochemical interactions of nanomaterials with plant cell wall model biosurfaces through both experimental and computational approaches. Nanomaterial-plant model cell wall interaction studies can guide the rational design of nanomaterials for more efficient delivery strategies in agriculture and elucidating their impact on the environment.

This work describes the synthesis of copper-loaded carbon dots and their application for suppressing Fusarium disease in tomatoes. These carbon dots could be an effective tool for delivering copper or chelating out heavy metals in plants.

Chemical imaging at high spatiotemporal resolution is crucial for advancing plant sciences and biotechnology. We demonstrate optical nanosensors for subcellular imaging of signaling molecules (H₂O₂) and lipid corona formation in plant tissues at high spatial (2O₂ waves (100 μM) from plant mesophyll to stomata and pavement cells. Ca²⁺ induced higher endogenous H₂O₂ in mesophyll cells, whereas organelle electron transport chain disruptors and salt stress generated similar H₂O₂ across all leaf cell types. Furthermore, the nanosensor quenching kinetics in photosynthetic mesophyll (0.018 s^-1) and epidermal (0.004 s^-1) cells enabled the detection of plant lipid corona formation. Optical nanosensors elucidate spatiotemporal dynamics of plant signaling molecules and advance our understanding of biocorona formation.

The impact of nanomaterial transformations on photosynthetic proteins remains largely unknown. We report positively charged iron oxide (Fe₃O₄) nanoparticles experience transformations in Arabidopsis thaliana plants in vivo that alter the formation and function of RuBisCO protein corona, a key carbon fixation enzyme. In vitro, negatively charged Fe₃O₄ nanoparticles impact the RuBisCO function but not their positively charged counterparts. Computational and in vitro proteomic analyses revealed that positively charged Fe₃O₄ nanoparticles preferentially bind to a RuBisCO small subunit that lacks active carboxylation sites. However, both positively and negatively charged nanoparticles decrease RuBisCO carboxylation activity after experiencing transformations in vivo by 3.0 and 1.7 times relative to the controls, respectively. The pH- and lipid-coating-dependent transformations that occur during nanoparticle transport across plant membranes enhance RuBisCO binding to positively charged nanoparticles affecting its distribution in chloroplasts. Elucidating the rules of how nanoparticle properties and transformations affect photosynthetic coronas is crucial for sustainable nano-enabled agriculture.

Nitrogen fertilizer delivery inefficiencies limit crop productivity and contribute to environmental pollution. Herein, we developed Zn- and Fe-doped hydroxyapatite nanomaterials (ZnHAU, FeHAU) loaded with urea (∼26% N) through hydrogen bonding and metal-ligand interactions. The nanomaterials attach to the leaf epidermal cuticle and localize in the apoplast of leaf epidermal cells, triggering a slow N release at acidic conditions (pH 5.8) that promote wheat (Triticum aestivum) growth and increased N uptake compared to conventional urea fertilizers. ZnHAU and FeHAU exhibited prolonged N release compared to urea in model plant apoplast fluid pH in vitro (up to 2 days) and in leaf membranes in plants (up to 10 days) with a high N retention (32% to 53%) under simulated high rainfall events (50 mm). Foliar N delivery doses of up to 4% as ZnHAU and FeHAU did not induce toxicity in plant cells. The foliar-applied ZnHAU and FeHAU enhanced fresh and dry biomass by ∼214% and ∼161%, and N uptake by ∼108% compared to foliar-applied urea under low soil N conditions in greenhouse experiments. Controlled N release by leaf-attached nanomaterials improves N delivery and use efficiency in crop plants, creating nanofertilizers with reduced environmental impact.

Plant genetic engineering methods are critical for food security and biofuel production and to enable molecular farming. Here, we elucidated how polymeric high aspect ratio nanocarriers can enable DNA delivery to Nicotiana benthamiana plants and transient expression. We demonstrated that a nanocarrier with 20 nm width, 80 nm length, and a polymer-to-DNA ratio of N/P = 3.0 afforded the most efficient DNA delivery and expression among the parameter space investigated. Additionally, we showed that polymer-DNA complexes with a moderate positive charge of ∼14 mV favored penetration through the cell wall and membranes with the assistance of cell wall degrading enzymes. Together, these results establish a narrow window of aspect ratios and charges of the nanocarrier-DNA complex that enables DNA delivery to plants using polymeric nanocarriers. This fundamental nanocarrier structure-function relationship informs the design of soft-material nanocarriers for nucleic acid delivery in plant cells to facilitate a wide range of plant biotechnology applications.

Mn ₃ O ₄ nanoparticles scavenged accumulated ROS and maintained stomatal aperture, thus improving cotton drought tolerance.

Current delivery practices for insecticide active ingredients are inefficient with only a fraction reaching their intended target. Herein, we developed carbon dot based nanocarriers with molecular baskets (γ-cyclodextrin) that enhance the delivery of active ingredients into insects (southern green stink bugs, Nezara viridula L.) via their tarsal pores. Nezara viridula feeds on leguminous plants worldwide and is a primary pest of soybeans. After two days of exposure, most of the nanocarriers and their active ingredient cargo (>85%) remained on the soybean leaf surface, rendering them available to the insects. The nanocarriers enter stink bugs through their tarsi, enhancing the delivery of a fluorescent chemical cargo by 2.6 times. The insecticide active ingredient nanoformulation (10 ppm) was 25% more effective in controlling the stink bugs than the active ingredient alone. Styletectomy experiments indicated that the improved active ingredient efficacy was due to the nanoformulation entering through the insect tarsal pores, consistent with fluorescent chemical cargo assays. This new nanopesticide approach offers efficient active ingredient delivery and improved integrated pest management for a more sustainable agriculture.