An easy-operation aptasensor for simultaneous detection of multiple tumor-associated exosomal proteins based on multicolor fluorescent DNA nanoassemblies

As a promising liquid biopsy biomarker, exosomes have demonstrated great potential and advantages in the noninvasive tumor diagnosis. However, an accurate and sensitive method for tumors-associated exosomes detection is scarce. Herein, we presented an easy-operation aptasensor which simultaneously detect multiple exosomal proteins by using multicolor fluorescent DNA nanoassemblies (FDNs) and CD63 aptamer-modified magnetic beads (MNPs-AptCD63). In this system, the FDNs were firstly constructed by encapsulating different quantum dots (QDs) into rolling circle amplification (RCA) products that contained different aptamer sequences. Thus, the FDNs could selectively recognize the different exosomal proteins captured by the MNPs-AptCD63, and achieve the multiplex and sensitive detection according to the fluorescence of QDs. Benefiting from the signal amplification capacity and high selectivity of FDNs, this aptasensor not only could detect exosomes as low as 650 particles/μL, but also showed accurate analysis in clinical samples. In addition, we can also achieve point-of-care testing (POCT) due to the simple analysis steps and naked-eye observable fluorescence of QDs under the ultraviolet irradiation. We believe that our aptasensor could provide a promising platform for exosomes-based personalized diagnosis and precise monitoring of human health.

Advances in DNA nanotechnology for chronic wound management: Innovative functional nucleic acid nanostructures for overcoming key challenges

Chronic wound management is affected by three primary challenges: bacterial infection, oxidative stress and inflammation, and impaired regenerative capacity. Conventional treatment methods typically fail to deliver optimal outcomes, thus highlighting the urgency to develop innovative materials that can address these issues and improve efficacy. Recent advances in DNA nanotechnology have garnered significant interest, particularly in the field of functional nucleic acid (FNA) nanomaterials, owing to their exceptional biocompatibility, programmability, and therapeutic potential. Among them, FNAs with unique nanostructures have garnered considerable attention. First, they inherit the biological properties of FNAs, including biocompatibility, reactive oxygen species (ROS)-scavenging capabilities, and modulation of cellular functions. Second, based on a precise design, these nanostructures exhibit superior physical properties, stability, and cellular uptake. Third, by leveraging the programmability of DNA strands, FNA nanostructures can be customized to accommodate therapeutic nucleic acids, peptides, and small-molecule drugs, thereby enabling a stable and controlled drug delivery system. These unique characteristics enable the use of FNA nanostructures to effectively address the major challenges in chronic wound management. This review focuses on various FNA nanostructures, including tetrahedral framework nucleic acids (tFNAs), DNA hydrogels, DNA origami, and rolling-circle amplification (RCA) DNA assembly. Additionally, a summary of recent advancements in their design and application for chronic wound management as well as insights for future research in this field are provided.

Aptamer-based assembly systems for SARS-CoV-2 detection and therapeutics

Nucleic acid aptamers are oligonucleotide chains with molecular recognition properties. Compared with antibodies, aptamers show advantages given that they are readily produced via chemical synthesis and elicit minimal immunogenicity in biomedicine applications. Notably, aptamer-encoded nucleic acid assemblies further improve the binding affinity of aptamers with the targets due to their multivalent synergistic interactions. Specially, aptamers can be engineered with special topological arrangements in nucleic acid assemblies, which demonstrate spatial and valence matching towards antigens on viruses, thus showing potential in the detection and therapeutic applications of viruses. This review presents the recent progress on the aptamers explored for SARS-CoV-2 detection and infection treatment, wherein applications of aptamer-based assembly systems are introduced in detail. Screening methods and chemical modification strategies for aptamers are comprehensively summarized, and the types of aptamers employed against different target domains of SARS-CoV-2 are illustrated. The evolution of aptamer-based assembly systems for the detection and neutralization of SARS-CoV-2, as well as the construction principle and characteristics of aptamer-based DNA assemblies are demonstrated. The typically representative works are presented to demonstrate how to assemble aptamers rationally and elaborately for specific applications in SARS-CoV-2 diagnosis and neutralization. Finally, we provide deep insights into the current challenges and future perspectives towards aptamer-based nucleic acid assemblies for virus detection and neutralization in nanomedicine.

Boosting Excited-State Energy Transfer by Anchoring Dipole Orientation in Binary Thermally Activated Delayed Fluorescence/J-Aggregate Assemblies

Förster resonance energy transfer (FRET) has been widely applied in fluorescence imaging, sensing and so on, while developing useful strategy of boosting FRET efficiency becomes a key issue that limits the application. Except optimizing spectral properties, promoting orientation factor (κ2) has been well discussed but rarely utilized for boosting FRET. Herein, we constructed binary nano-assembling of two thermally activated delayed fluorescence (TADF) emitters (2CzPN and DMAC-DPS) with J-type aggregate of cyanine dye (C8S4) as doping films by taking advantage of their electrostatic interactions. Time-resolved spectroscopic measurements indicated that 2CzPN/Cy-J films exhibit an order of magnitude higher kFRET than DMAC-DPS/Cy-J films. Further quantitative analysing on kFRET and kDET indicated higher orientation factor (κ2) in 2CzPN/Cy-J films play a key role for achieving fast kFRET, which was subsequently confirmed by anisotropic measurements. Corresponding DFT/TDDFT calculation revealed strong "two-point" electrostatic anchoring in 2CzPN/Cy-J films that is responsible for highly orientated transitions. We provide a new strategy for boosting FRET in nano-assemblies, which might be inspired for designing FRET-based devices of sensing, imaging and information encryption.

Dual-signal amplified electrochemical aptasensor based on Au/MrGO and DNA nanospheres for ultra-sensitive detection of BPA without directly modified working electrode

Rapid and sensitive analysis of bisphenol A (BPA) is essential for preventing health risks to humans and animals. Hence, a signal-amplified electrochemical aptasensor without repetitive polishing and modification of working electrode was developed for BPA using Au-decorated magnetic reduced graphene oxide (Au/MrGO)-based recognition probe (RP) and DNA nanospheres (DNS)-based signal probe (SP) cooperative signal amplification. The DNS served as a signal molecule carrier and signal amplifier, while Au/MrGO acted as a signal amplifier and excellent medium for magnetic adsorption and separation. Moreover, utilizing the excellent magnetic properties of Au/MrGO eliminates the need for repetitive polishing and multi-step direct modification of the working electrode while ensuring that all detection processes take place in solution and that used Au/MrGO can be easily recycled. The proposed aptasensor exhibited not only good stability and selectivity, but also excellent sensitivity with a limit of detection (LOD) of 8.13 fg/mL (S/N = 3). The aptasensor's practicality was proven by spiking recovery tests on actual water samples and comparing the results with those detected by HPLC. The excellent sensitivity and selectivity make this aptasensor an alternative and promising avenue for rapid detection of BPA in environmental monitoring.

Recent advances in the synthesis of single-stranded DNA in vitro

Single-stranded DNA (ssDNA) is the foundation of modern biology, with wide applications in gene editing, sequencing, DNA information storage, and materials science. However, synthesizing ssDNA with high efficiency, high throughput, and low error rate in vitro remains a major challenge. Various methods have been developed for ssDNA synthesis, and some significant results have been achieved. In this review, six main methods were introduced, including solid-phase oligonucleotide synthesis, terminal deoxynucleotidyl transferase-based ssDNA synthesis, reverse transcription, primer exchange reaction, asymmetric polymerase chain reaction, and rolling circle amplification. The advantages and limitations of each method were compared, as well as illustrate their representative achievements and applications. Especially, rolling circle amplification has received significant attention, including ssDNA synthesis, assembly, and application based on recent work. Finally, the future challenges and opportunities of ssDNA synthesis were summarized and discussed. Envisioning the development of new methods and significant progress will be made in the near future with the efforts of scientists around the world.

Polymer-DNA assembled nanoflower for targeted delivery of dolastatin-derived microtubule inhibitors

Dolastatin derivatives possess excellent anticancer activity and have been translated into clinical trials for cancer therapy. Drug delivery systems enable dolastatin derivatives to break the limitation of instability during blood circulation and ineffective cell internalization in the application. Nevertheless, their potential has not been thoroughly established because of the limited loading efficacy and complicated chemical modification. Herein, we rationally propose a rolling circle amplification-based polymer-DNA assembled nanoflower for targeted and efficient delivery of dolastatin-derived drugs to achieve efficient anticancer therapy. The polymer-DNA assembled nanoflower with targeted aptamer conjugate is widely applicable for loading dolastatin-derived drugs with high encapsulation efficiency. The developed monomethyl auristatin E (MMAE) loaded PN@M exhibited increased cellular uptake and enhanced inhibitory effect, especially in multidrug-resistant tumor cells. The results of in vivo anticancer effects indicate that nanoflower as a dolastatin derivatives delivery system holds considerable potential for the treatment of malignant cancer.

Dual-function transaminases with hybrid nanoflower for the production of value-added chemicals from biobased levulinic acid

The U.S. Department of Energy has listed levulinic acid (LA) as one of the top 12 compounds derived from biomass. LA has gained much attention owing to its conversion into enantiopure 4-aminopentanoic acid through an amination reaction. Herein, we developed a coupled-enzyme recyclable cascade employing two transaminases (TAs) for the synthesis of (S)-4-aminopentanoic acid. TAs were first utilized to convert LA into (S)-4-aminopentanoic acid using (S)-α-Methylbenzylamine [(S)-α-MBA] as an amino donor. The deaminated (S)-α-MBA i.e., acetophenone was recycled back using a second TAs while using isopropyl amine (IPA) amino donor to generate easily removable acetone. Enzymatic reactions were carried out using different systems, with conversions ranging from 30% to 80%. Furthermore, the hybrid nanoflowers (HNF) of the fusion protein were constructed which afforded complete biocatalytic conversion of LA to the desired (S)-4-aminopentanoic acid. The created HNF demonstrated storage stability for over a month and can be reused for up to 7 sequential cycles. A preparative scale reaction (100 mL) achieved the complete conversion with an isolated yield of 62%. Furthermore, the applicability of this recycling system was tested with different β-keto ester substrates, wherein 18%-48% of corresponding β-amino acids were synthesized. Finally, this recycling system was applied for the biosynthesis of pharmaceutical important drug sitagliptin intermediate ((R)-3-amino-4-(2,4,5-triflurophenyl) butanoic acid) with an excellent conversion 82%.

A functional nucleic acid-based fluorescence sensing platform based on DNA supersandwich nanowires and cation exchange reaction

Accurate and sensitive analysis of p53 DNA is important for early diagnosis of cancer. In this work, a fluorescence sensing system based on DNA supersandwich nanowires and cation exchange (CX)-triggered multiplex signal amplification was constructed for the detection of p53 DNA. In the presence of p53 DNA, the DNA self-assembles to form a DNA supersandwich nanowire that generates long double-stranded DNA. Subsequently, the cation exchange (CX) reaction between ZnS and Ag+ was utilized to release free Zn2+. With the participation of Zn2+, DNAzyme catalyzes the hydrolysis of numerous catalytic molecular beacons, resulting in a greatly enhanced fluorescence signal due to the cycling of DNAzyme. The fluorescence values increased in proportion to the concentrations of p53 DNA in the range of 10 pM to 200 nM, and a detection limit (LOD) of 2.34 pM (S/N = 3) was obtained. This method provides an effective strategy for the quantitative detection of p53 DNA.

AMP Aptamer Programs DNA Tile Cohesion without Canonical Base Pairing

Tile-based DNA self-assembly provides a versatile approach for the construction of a wide range of nanostructures for various applications such as nanomedicine and advanced materials. The inter-tile interactions are primarily programmed by base pairing, particularly Watson-Crick base pairing. To further expand the tool box for DNA nanotechnology, herein, we have designed DNA tiles that contain both ligands and aptamers. Upon ligand-aptamer binding, tiles associate into geometrically well-defined nanostructures. This strategy has been demonstrated by the assembly of a series of DNA nanostructures, which have been thoroughly characterized by gel electrophoresis and atomic force microscopy. This new inter-tile cohesion could bring new potentials to DNA self-assembly in the future. For example, the addition of free ligand could modulate the nanostructure formation. In the case of biological ligands, DNA self-assembly could be related to the presence of certain ligands.

Implementing Logic Gates by DNA Crystal Engineering

DNA self-assembly computation is attractive for its potential to perform massively parallel information processing at the molecular level while at the same time maintaining its natural biocompatibility. It has been extensively studied at the individual molecule level, but not as much as ensembles in 3D. Here, the feasibility of implementing logic gates, the basic computation operations, in large ensembles: macroscopic, engineered 3D DNA crystals is demonstrated. The building blocks are the recently developed DNA double crossover-like (DXL) motifs. They can associate with each other via sticky-end cohesion. Common logic gates are realized by encoding the inputs within the sticky ends of the motifs. The outputs are demonstrated through the formation of macroscopic crystals that can be easily observed. This study points to a new direction of construction of complex 3D crystal architectures and DNA-based biosensors with easy readouts.

Functional DNA Superstructures Exhibit Positive Homotropic Allostery in Ligand Binding

Inspired by intrinsically disordered proteins in nature, DNA aptamers can be engineered to display strongly homotropic allosteric (or cooperative) ligand binding, representing a unique feature that could be of great utility in applications such as biosensing, imaging and drug delivery. The use of an intrinsic disorder mechanism, however, comes with an inherent drawback of significantly reduced overall binding affinity. We hypothesize that it could be addressed via the design of multivalent supramolecular aptamers. We built functional DNA superstructures (denoted as 3D DNA), made of long-chain DNA containing tandem repeating DNA aptamers (or concatemeric aptamers). The 3D DNA systems exhibit highly cooperative binding to both small molecules and proteins, without loss of binding affinities of their parent aptamers. We further produced a highly responsive sensor for fluorescence imaging of glutamate stimulation-evoked adenosine triphosphate (ATP) release in neurons, as well as force stimulus-triggered ATP release in astrocytes.

Design of supramolecular hybrid nanomaterials comprising peptide-based supramolecular nanofibers and in situ generated DNA nanoflowers through rolling circle amplification

The artificial construction of multicomponent supramolecular materials comprising plural supramolecular architectures that are assembled orthogonally from their constituent molecules has attracted growing attention. Here, we describe the design and development of multicomponent supramolecular materials by combining peptide-based self-assembled fibrous nanostructures with globular DNA nanoflowers constructed by the rolling circle amplification reaction. The orthogonally constructed architectures were dissected by fluorescence imaging using the selective fluorescence staining procedures adapted to this study. The present, unique hybrid materials developed by taking advantage of each supramolecular architecture based on their peptide and DNA functions may offer distinct opportunities to explore their bioapplications as a soft matrix.

An Ultrasensitive Electrochemical Biosensor Integrated by Nicking Endonuclease-Assisted Primer Exchange Reaction Cascade Amplification and DNA Nanosphere-Mediated Electrochemical Signal-Enhanced System for MicroRNA Detection

Specific and sensitive microRNAs (miRNAs) detection is essential to early cancer diagnosis. The development of these technologies including functional nuclease-mediated target amplification and DNA nanotechnology possesses tremendous potential for the high-performance detection of miRNAs in the accurate diagnosis of disease. In this study, we have established an ultrasensitive electrochemical biosensor by combining nicking endonuclease-assisted primer exchange reaction (PER) cascade amplification with a DNA nanosphere (DNS)-mediated electrochemical signal-enhanced system for the detection of miRNA-21 (miR-21). The cascade amplification is initiated by a nicking endonuclease that can cleave specific DNA substrates and highly amplify translation of the target to single-stranded DNA fragments (sDNA). Then, the PER cascade is powered by strand-displacing polymerase and generates a large amount of nascent single-stranded connector DNA (cDNA) via sDNA triggering of the dumbbell probe (DP), thus achieving the cascade amplification of the target. Finally, the DNS loaded with plenty of electroactive substances can be captured on the electrode via cDNA for further enhancing the electrochemical signal and highly sensitive detection of miR-21. The proposed electrochemical biosensor exhibits a wide detection range of 1 aM to 0.1 nM and a low detection limit of 0.58 aM. The excellent selectivity allows the biosensor to discriminate miR-21 from other miRNAs, even the one base-mismatched sequence. Moreover, the practicability of the biosensor is investigated by analyzing miR-21 in human serum and cancer cell lysate. Therefore, our proposed nicking endonuclease-assisted PER cascade amplification strategy provides a powerful platform for the early detection of miRNA-related disease and molecular diagnosis.

Novel DNA nanoflower biosensing technologies towards next-generation molecular diagnostics

DNA nanoflowers (DNFs) are topological flower-like nanostructures based on ultralong-strand DNA and inorganic metal-ion frameworks. Because of their programmability, biocompatibility, and controllable assembly size for specific responses to molecular recognition stimuli, DNFs are powerful biosensing tools for detecting biomolecules. Here, we review the current state of DNF-based biosensing strategies for in vivo and in vitro detection, with a view of how the field has evolved towards molecular diagnostics. We also provide a detailed classification of DNF-based biosensing strategies and propose their future utility. Particularly as transduction elements, DNFs can accelerate biosensing engineering by signal amplification. Finally, we discuss the key challenges and further prospects of DNF-based biosensing technologies in developing applications of a broader scope.

Aptamer-conjugated carbon-based nanomaterials for cancer and bacteria theranostics: A review

Aptamers are single-stranded oligonucleotides that link to various substrates with great affinity and selectivity, including small molecules, peptides, proteins, cells, and tissues. For this reason, they can be used as imaging agents for cancer imaging techniques. Multifunctional nanomaterials combined with imaging probes and drugs are promising cancer diagnosis and treatment candidates. On the other hand, carbon-based nanomaterials (CNMs), including such as fullerene, carbon nanotubes, carbon-based quantum dots, carbon nanohorns, graphene oxide and its derivatives carbon nanodots, and nanodiamonds, are sort of smart materials that can be used in a variety of theranostic applications, including photo-triggered therapies. The remarkable physical characteristics, functionalizable chemistry, biocompatibility, and optical properties of these nanoparticles have enabled their utilization in less-invasive therapies. The theranostic agents that emerged by combining aptamers with CNMs have opened a novel alternative for personified medicine of cancer, target-specific imaging, and label-free diagnosis of a broad range of cancers, as well as pathogens. Aptamer-functionalized CNMs have been used as nanovesicles for targeted delivery of anti-cancer agents (i.e., doxorubicin and 5-fluorouracil) to tumor sites. Furthermore, these CNMs conjugated with aptamers have shown great advantages over standard CNMs to sensitively detect Mycobacterium tuberculosis, Escherichia coli, staphylococcus aureus, Vibrio parahaemolyticus, Salmonella typhimurium, Pseudomonas aeruginosa, and Citrobacter freundii. Regrettably, CNMs can form compounds defined as NOAA (nano-objects, and their aggregates and agglomerates larger than 100 nm), that accumulate in the body and cause toxic effects. Surface modification and pretreatment with albumin avoid agglomeration and increase the dispersibility of CNMs, so it is needed to guarantee the desirable interactions between functionalized CNMs and blood plasma proteins. This preliminary review aimed to comprehensively discuss the features and uses of aptamer-conjugated CNMs to manage cancer and bacterial infections.

Construction of branched DNA-based nanostructures for diagnosis, therapeutics and protein engineering

Branched DNA with multibranch-like anisotropic topology serves as a promising and powerful building block in constructing multifunctional-integrated nanomaterials in a programmable and controllable manner. Recently, a series of branched DNA-based functional nanomaterials were developed by elaborate molecular design. In this review, we focused on the construction of branched DNA-based nanostructures for biological and biomedical applications. First, the molecular design and synthesis method of branched DNA monomer were briefly described. Then, the construction strategies of branched DNA-based nanostructures were categorially discussed, including target-triggered polymerization, enzymatic extension and hybrid assembly. Finally, the biological and biomedical applications including diagnosis, therapeutics and protein engineering were summarized. We envision that the review will contribute to the further development of branched DNA-based nanomaterials with great application potential in the field of biomedicine, thus building a new bridge between material chemistry and biomedicine.

DNA Functional Nanomaterials for Controlled Delivery of Nucleic Acid-Based Drugs

Nucleic acid-based drugs exhibited great potential in cancer therapeutics. However, the biological instability of nucleic acid-based drugs seriously hampered their clinical applications. Efficient in vivo delivery is the key to the clinical application of nucleic acid-based drugs. As a natural biological macromolecule, DNA has unique properties, such as excellent biocompatibility, molecular programmability, and precise assembly controllability. With the development of DNA nanotechnology, DNA nanomaterials have demonstrated significant advantages as delivery vectors of nucleic acid-based drugs by virtue of the inherent nucleic acid properties. In this study, the recent progress in the design of DNA-based nanomaterials for nucleic acid delivery is summarized. The DNA nanomaterials are categorized according to the components including pure DNA nanomaterials, DNA-inorganic hybrid nanomaterials, and DNA-organic hybrid nanomaterials. Representative applications of DNA nanomaterials in the controlled delivery of nucleic acid-based drugs are exemplified to show how DNA nanomaterials are rationally and exquisitely designed to address application issues in cancer therapy. At the end of this study, the challenges and future development of DNA nanomaterials are discussed.

Digital Counting of Biomolecules Using Engineered Functional DNA Superstructures

There is currently a great need for developing a simple and effective biosensing platform for the detection of single biomolecules (e.g., DNAs, RNAs, or proteins) in the biological, medical, and environmental fields. Here, we show a versatile and sensitive fluorescence counting strategy for quantifying proteins and microRNAs by employing functional DNA superstructures (denoted as 3D DNA). A 3D DNA biolabel was first engineered to become highly fluorescent and carry recognition elements for the target of interest. The presence of a target cross-links the resultant of the 3D DNA biolabel and a surface-bound capturing antibody or DNA oligonucleotide, thus forming a sandwich complex that can be easily resolved using traditional fluorescence microscopy. The broad utility of this platform is illustrated by engineering two different 3D DNA biolabels that enable the quantification of β-lactamase (one secreted bacterial hydrolase) and miR-21 (one overexpressed microRNA in cancer cells) with detection limits of 100 aM and 1 fM, respectively. We envision that the approach described herein will find useful applications in chemical biology, medical diagnostics, and biosensing.

Fast-responding functional DNA superstructures for stimuli-triggered protein release

Strategies that speed up the on-command release of proteins (e.g., enzymes) from stimuli-responsive materials are intrinsically necessary for biosensing applications, such as point-of-care testing, as they will achieve fast readouts with catalytic signal-amplification. However, current systems are challenging to work with because they usually exhibit response times on the order of hours up to days. Herein, we report on the first effort to construct a fast-responding gating system using protein-encapsulating functional DNA superstructures (denoted as protein@3D DNA). Proteins were directly embedded into 3D DNA during the one-pot rolling circle amplification process. We found that the specific DNA-DNA interaction and aptamer-ligand interaction could act as general protocols to release the loaded proteins from 3D DNA. The resulting gating system exhibits fast release kinetics on the order of minutes. Taking advantage of this finding, we designed a simple paper device by employing protein@3D DNA for colorimetric detection of toxin B (Clostridium difficile marker). This device is capable of detecting 0.1 nM toxin B within 16 minutes.

Multifunctional DNA dendrimer nanostructures for biomedical applications

DNA nanomaterials have attracted ever-increasing attention over the past decades due to their incomparable programmability and multifunctionality. In particular, DNA dendrimer nanostructures, as a major research focus, have been applied in the fields of biosensing, therapeutics, and protein engineering, benefiting from their highly branched configuration. With the aid of specific recognition probes and inherent signal amplification, DNA dendrimers can achieve ultrasensitive detection of nucleic acids, proteins, cells, and other substances, such as lipopolysaccharides (LPS), adenosine triphosphate (ATP), and exosomes. By virtue of their void-containing structures and biocompatibility, DNA dendrimers can deliver drugs or functional nucleic acids into target cells in chemotherapy, immunotherapy, and gene therapy. Furthermore, DNA dendrimers are being applied in protein engineering for efficient directed evolution of proteins. This review summarizes the main research progress of DNA dendrimers, concerning their assembly methods and biomedical applications as well as the emerging challenges and perspectives for future research.

Best served small: nano battles in the war against wound biofilm infections

The global challenge of antimicrobial resistance is of increasing concern, and alternatives to currently used antibiotics or methods to improve their stewardship are sought worldwide. Microbial biofilms, complex 3D communities of bacteria and/or fungi, are difficult to treat with antibiotics for several reasons. These include their protective coats of extracellular matrix proteins which are difficult for antibiotics to penetrate. Nanoparticles (NP) are one way to rise to this challenge; whilst they exist in many forms naturally there has been a profusion in synthesis of these small (<100 nm) particles for biomedical applications. Their small size allows them to penetrate the biofilm matrix, and as well as some NP being inherently antimicrobial, they also can be modified by doping with antimicrobial payloads or coated to increase their effectiveness. This mini-review examines the current role of NP in treating wound biofilms and the rise in multifunctionality of NP.