Spherical nucleic acids for biomedical applications

Spherical nucleic acids(SNAs)are a 3D spherical nanostructure composed of highly oriented,dense layers of oligonucleotides conjugated to a hollow or solid core.This structure allows SNAs to show resistance to nuclease degradation,enter into nearly all cells without transfection agents and enable precise interactions with target molecules.Based on superior biological properties,SNAs can be tailored for diverse biological applications,rendering them a flexible and biosafe tool for biological applications as well as an enabling platform for therapy.In this review,we mainly discuss the structure and conjugation mode of SNAs and focus on recent advances in their applications,such as biomedical detection,imaging,and drug delivery.Finally,the remaining challenges and future directions of SNAs are also discussed and proposed.

Ultrasound-responsive spherical nucleic acid against c-Myc/PD-L1 to enhance anti-tumoral macrophages in triple-negative breast cancer progression

Triple-negative breast cancer(TNBC)is the most challenging breast cancer subtype because of its aggressive behavior and limited therapeutic targets.c-Myc is hyperactivated in the majority of TNBC tissues,however,it has been considered an“undruggable”target due to its disordered structure.Herein,we developed an ultrasound-responsive spherical nucleic acid(SNA)against c-Myc and PD-L1 in TNBC.It is a self-assembled and carrier-free system composed of a hydrophilic small-interfering RNA(si RNA)shell and a hydrophobic core made of a peptide nucleic acid(PNA)-based antisense oligonucleotide(ASO)and a sonosensitizer.We accomplished significant enrichment in the tumor by enhanced permeability and retention(EPR)effect,the controllable release of effective elements by ultrasound activation,and the combination of targeted therapy,immunotherapy and physiotherapy.Our study demonstrated significant anti-tumoral effects in vitro and in vivo.Mass cytometry showed an invigorated tumor microenvironment(TME)characterized by a significant alteration in the composition of tumor-associated macrophages(TAM)and decreased proportion of PD-1-positive(PD-1+)T effector cells after appropriate treatment of the ultrasound-responsive SNA(USNA).Further experiments verified that tumor-conditioned macrophages residing in the TME were transformed into the anti-tumoral population.Our finding offers a novel therapeutic strategy against the“undruggable”c-Myc,develops a new targeted therapy for c-Myc/PD-L1 and provides a treatment option for the TNBC.

R11 peptides can promote the molecular imaging of spherical nucleic acids for bladder cancer margin identification

One of the critical problems in bladder cancer(BC)management is the local recurrence of disease.However,achieving the accurate delineation of tumor margins intraoperatively remains extremely difficult due to the lack of effective tumor margin recognition technology.Herein,survivin molecular beacon(MB)and R11 peptide-linked spherical nucleic acids(SNAs)were synthesized as nanoprobes(AuNP-MB@R11)for sensitive detection of BC margins.Physicochemical properties proved that R11 peptides and survivin MB were successfully loaded onto the surface of SNAs.AuNP-MB@R11 had good stability against nuclease activity and high sensitivity and specificity to detect survivin single strand DNA(ssDNA)in vitro.According to cytology,R11 peptides could increase the BC targeting ability and membrane penetrability of SNAs.Notably,R11 peptides significantly promoted the disintegration of lysosomes and the release of SNAs to enhance fluorescence imaging quality.Further RNA sequencing proved that some genes and pathways related to endocytosis and lysosomes were significantly regulated,such as AGPAT5,GPD1L,and GRB2.In orthotopic BC models and a clinical sample from a patient with BC,AuNP-MB@R11 showed a more legible cancerous fluorescence margin and offered remarkably improved detection compared to those achieved by SNAs.R11 peptide-linked SNAs present promising potential to identify BC margin,which may help to improve the R0 resection rate in surgery and improve patients’quality of life.

Spherical Nucleic Acid-Amplified Digital Flow Cytometric Bead Assay for the Ultrasensitive Detection of Protein and Exosome

Comprehensive Summary,Most conventional digital bioassays rely on the use of fully-sealed microchambers as independent units to compartmentalize the target molecules and the signal generation reaction,which require specialized equipment or proprietary reagents/consumables.Herein,we report a microchamber-free and spherical nucleic acid(SNA)-amplified digital flow cytometric bead assay(dFBA)for ultrasensitive protein and exosome analysis with simple workflows,easily accessible instruments/reagents,and high discriminating ability towards the fluorescence-positive and fluorescence-negative beads.In this dFBA,microbeads are employed as independent carriers to anchor the single target molecule-initiated signal amplification reaction,avoiding the use of sealed droplets or microwell microchambers.Meanwhile,antibody-functionalized SNAs(FSNAs)with a high density of DNA probes act as a bridge for efficiently amplified target-to-DNA signal conversion,which allows the use of DNA-based rolling circle amplification(RCA)as the fluorescence signal amplification technique to quantify non-nucleic acid targets.Even a single target-induced on-bead RCA and fluorescence enriching are sufficient to make the target-loaded bead bright enough to be clearly discriminated from the negative ones just by use of a most common flow cytometer(FCM).This dFBA has successfully realized the digital analysis of ultralow levels of protein and exosome biomarkers,enlarging the toolbox of digital bioassays for clinical applications.

Cascaded DNA circuits-programmed self-assembly of spherical nucleic acids for high signal amplification

Signal amplification is an important issue in DNA nanotechnology and molecular diagnostics.In this work,we report a strategy for the catalytic self-assembly of spherical nucleic acids(SNAs)programmed by two-layer cascaded DNA circuits through integrating an entropy-driven catalytic network,a catalytic hairpin assembly circuit,and a facile SNA assembly-based reporter system.This integrated system could implement^100,000-fold signal amplification in the presence of 1 pM of input target.Possessing powerful amplification ability of nucleic acid signal,our strategy should be of great potential in fabricating more robust dynamic networks to be applied for signal transduction,DNA computing,and nucleic acid-based diagnostics.

Spherical nucleic acids:Organized nucleotide aggregates as versatile nanomedicine

Spherical nucleic acids(SNAs)are composed of a nanoparticle core and a layer of densely arranged oligonucleotide shells.After the first report of SNA by Mirkin and coworkers in 1996,it has created a significant interest by offering new possibilities in the field of gene and drug delivery.The controlled aggregation of oligonucleotides on the surface of organic/inorganic nanoparticles improves the delivery of genes and nucleic acid–based drugs and alters and regulates the biological profiles of the nanoparticle core within living organisms.Here in this review,we present an overview of the recent progress of SNAs that has speeded up their biomedical application and their potential transition to clinical use.We start with introducing the concept and characteristics of SNAs as drug/gene delivery systems and highlight recent efforts of bioengineering SNA by imaging and treatmenting various diseases.Finally,we discuss potential challenges and opportunities of SNAs,their ongoing clinical trials,and future translation,and how they may affect the current landscape of clinical practices.We hope that this review will update our current understanding of SNA,organized oligonucleotide aggregates,for disease diagnosis and treatment.