Kyung Ho Kim

Accurate and rapid nucleic acid detection is vital for the early diagnosis of infectious diseases. Conventional polymerase chain reaction (PCR) offers high sensitivity but is hindered by bulky equipment, long processing times, and the need for technical expertise, limiting its point‐of‐care testing (POCT) applications. To overcome these constraints, we developed an innovative photonic PCR system utilizing the plasmonic photothermal effect of a gold nanofilm to accelerate the amplification process. This system integrates a lateral flow assay (LFA) for the streamlined visual detection of FITC‐ and biotin‐labeled Seoul orthohantavirus (SEOV) amplicons using gold nanoparticle‐conjugated antibodies. By synergizing photonic PCR with LFA, we achieved real‐time‐like detection of target products within 15 min (excluding the extraction step). This integrated platform demonstrates a limit of detection (LOD) of 150 copies/mL of the template genome, significantly enhancing diagnostic sensitivity. Our design prioritizes simplicity and efficiency, eliminating the requirement for sophisticated instrumentation or extensive operator training. Given its rapid processing, cost‐effectiveness, and high sensitivity, this photonic PCR‐LFA system represents a compelling solution for diverse diagnostic applications, including clinical diagnostics, environmental monitoring, and field‐based testing. This advancement underscores the potential of plasmon‐driven materials in transforming next‐generation molecular POCT platforms.

The aim of this review article is to provide a summary of the state-of-the-art technology for the integration of lipid-based natural biomaterials, emphasizing mainly broad applications, especially in therapeutics and diagnostics. Herein, we focused mainly on the utilization of bioengineered lipid-based nanomaterials as medicine and diagnostic agents, which constitute the primary focus of the field of bioengineered lipid-based nanomaterials. Each property of diverse classes of lipid-based nanomaterials is determined by their chemical structure, functionality, and synthesis methodology, and they are versatile for use as drug-delivery nanocarriers, for targeting certain types of cancer cells and for controlled immune therapies. In addition, lipid-based biomaterials have been applied in various research fields with subsequent surface engineering with modulation moieties for the integration of functional nanomaterials (signaling pathway mediators, nucleic acid drugs, and active targeting proteins). The overall manuscript is organized in sections describing materials, fabrication processes, and applications based on innovative lipid-based nanobiotechnology.

Periodontal disease results from an imbalance between bacterial complexes and the immune system. However, periodontal disease diagnosis is limited by its time-consuming nature, long processing time, and high costs. In this study, we suggest an ultrafast, highly sensitive, and multitargeted plasmonic photothermal-based digital polymerase chain reaction (dPCR) method using a novel plasmonic photothermal-based dPCR chip combined with photothermal materials and organic interfacial chemicals for periodontal disease diagnosis. This platform can detect biofilm-forming bacteria (Streptococcus mutans), red complex bacteria (Porphyromonas gingivalis), and orange complex bacteria (Campylobacter rectus and Prevotella nigrescens). The ultrafast plasmonic photothermal-based dPCR technique amplified multiple target genes over 45 cycles within 14 min, and a fluorescence scanning system measured the fluorescence intensity within 9 min. The sensitivity of detection of standard bacteria and artificial saliva containing bacteria showed a sensitivity of 10¹ copies/μL. Furthermore, multiplex PCR was performed with a plasmonic photothermal-based dPCR device to confirm the possibility of multiplex PCR of bacterial mixtures containing four species. This plasmonic photothermal-based dPCR platform can be utilized as a point-of-care molecular diagnostic device for the ultrafast diagnosis of diseases in real-time in various fields.

A highly accurate and sensitive monitoring platform for wastewater is needed for the detection of wastewater borne pathogens. For the fabrication of an environmental monitoring platform, an aptamer-integrated graphene field-effect transistor (GFET) platform was presented. The detection of pathogenic bacteria living in wastewater is an excellent method for confirming water quality. Here, we developed a target-specific aptamer-loaded GFET for the verification of purified wastewater. Dual graphene channels were micropatterned on the substrate, and each channel was immobilized with an aptamer linked to a chemical linker compound. Pretreated sewage was screened with our newly developed platform, and the detection performance was 10¹ cfu mL^-1 for multidrug-resistant Acinetobacter baumannii and 10¹ cfu mL^-1 for methicillin-resistant Staphylococcus aureus, with a measurement range of 10¹ to 10⁶ cfu mL^-1. Additionally, in the presence of impurities, the platform showed a highly accurate binding affinity between the target and biomolecule without noise caused by interference effects.

The development of nanodrugs targeting multidrug-resistant bacteria, while sparing the beneficial constituents of the microbiome, has emerged as a promising approach to combat disease and curb the rise of antimicrobial resistance. In this investigation, we devised a siderophore-functionalized nanodrug based on a gold nanoparticle construct (AuNP-NSC; Gold nanoparticle_N-heterocyclic_Siderophore_Cyanine7), offering an innovative treatment modality against drug-resistant bacterial pathogens. As a proof of concept, the efficacy of this nanodrug delivery and antimicrobial therapy was evaluated against the notoriously resistant bacterium P. aeruginosa. N-Heterocyclic carbenes (NHCs) exhibit a strong affinity for transition metals, forming highly stable complexes resistant to ligand displacement. The entry of siderophore-conjugated nanodrugs into bacteria is facilitated through specific receptors on the outer membrane. In our study, AuNP-NSC was specifically targeted and imported into resistant Gram-negative P. aeruginosa via binding with ferric iron. Treatment with the developed nanodrug significantly inhibited the proliferation of antibiotic-resistant P. aeruginosa, reducing bacterial counts by more than 95% and mitigating drug resistance. Furthermore, AuNP-NSC markedly diminished P. aeruginosa-induced skin lesions and forestalled systemic organ failure triggered by secondary sepsis in mouse models. These findings underscore the potential of nanodrugs as specialized therapeutic agents for the management of antibiotic-resistant bacterial infections.

Kyung Ho Kim, Sung Eun Seo, and Oh Seok Kwon. Applied Science and Convergence Technology 2024;33:167-70. https://doi.org/10.5757/ASCT.2024.33.6.167

Interfacial chemicals for metal surface functionalization were developed for applications of high water dispersibility and environmental stability. Metal nanomaterials, i.e., gold nanoparticles (AuNPs), were synthesized by introducing various interfacial chemicals, to improve the hydrophilicity of biosensors, such as those used in fluorescence resonance energy transfer (FRET) and lateral flow assay (LFA), respectively. Previously, thiolated AuNPs (SH-AuNPs) exhibited colloidal instability by forming irreversible aggregates in extreme environmental conditions; this phenomenon led to limitations such as poor sensitivity and reproducibility, in terms of biosensor application fields. Therefore, the development of novel interfacial chemicals remained a challenge for AuNP-based biosensor applications. Here, we first synthesized and demonstrated an ultra-stable AuNP functionalization by introducing N-heterocyclic carbene (NHC) compounds with a polyethylene glycol chain and azide terminal groups (NHC-AuNPs). The high binding energy of NHC-AuNPs compared with SH-AuNPs was demonstrated by density functional theory simulation, with NHC-AuNPs showing an unprecedented stability in extreme environmental conditions with varying ranges of pH, salts, and temperature; in particular, ultra-stability was observed in condition by freezing/thawing over 120 times. NHC-AuNPs were applied FRET and LFA biosensors and showed excellent sensing performances. Based on the results, NHC-AuNPs can be introduced for performance improvement in the development of diagnostic platforms to utilize in extreme environmental conditions.

Fatal pathogenic organisms have been detected by various point‐of‐care tests (PoCTs) in clinical samples. PoCTs based on portable electrical devices are able to detect organisms in simple and rapid method. Although electrical PoCT devices show ultra sensitivity when detecting pathogens in standard samples, their industrialization has been limited due to low reproducibility, sensitivity, and specificity, resulting from nonspecific binding issues by media. In this research, a perpendicular N‐heterocyclic carbene self‐assembled monolayer (NHC‐SAM) conjugated on graphene micropattern field‐effect transistors (NGMFETs) is first demonstrated for monitoring pathogens. Two single bonds of NHCSAM on GM are investigated via density functional theory (DFT) and surface analyses. Bioreceptors are conjugated on the side gate‐modulated NGMFET for ultra‐stable on‐site detection. The side‐gated BNGMFETs system displayed remarkable performance in the detection of the following: i) SARS‐CoV‐2 spike protein S1 (limit of detection (LOD): ≈10 pg mL⁻¹) in CTM, ii) O. tsutsugamushi Ab (LOD: ≈1 pg mL⁻¹), and iii) E. coli (LOD: 10° CFU mL⁻¹) in serum. Compared to commercial methodology, the platform presents 10² times higher LODs towards those pathogens in clinical samples with higher reproducibility. Based on these results, side‐gated BNGMFETs can be utilized as universal PoCT during pandemics.

The transmission and pathogenesis of highly contagious fatal respiratory viruses are increasing, and the need for an on‐site diagnostic platform has arisen as an issue worldwide. Furthermore, as the spread of respiratory viruses continues, different variants have become the dominant circulating strains. To prevent virus transmission, the development of highly sensitive and accurate on‐site diagnostic assays is urgently needed. Herein, a facile diagnostic device is presented for multi‐detection based on the results of detailed receptor‒ligand dynamics simulations for the screening of various viral strains. The novel bioreceptor‐treated electronics (receptonics) device consists of a multichannel graphene transistor and cell‐entry receptors conjugated to N‐heterocyclic carbene (NHC). An ultrasensitive multi‐detection performance is achieved without the need for sample pretreatment, which will enable rapid diagnosis and prevent the spread of pathogens. This platform can be applied for the diagnosis of variants of concern in clinical respiratory virus samples and primate models. This multi‐screening platform can be used to enhance surveillance and discriminate emerging virus variants before they become a severe threat to public health.