Design,Synthesis And Biomedical Applications Of Emerging Two-dimensional Mxene And Silicene

Two-dimensional?2D?nanomaterials represent an emerging category of nanomaterials that feature sheet-like microstructure with the lateral-size ranging from a few nanometers to hundreds of nanometers and even larger,but the thickness of single-or few-atom.Novoselov,Geim and co-workers exfoliated graphene from graphite using the mechanical cleavage method in 2004.Although the exploration of2D layered materials dates back several decades,the marked ultrathin 2D atomic crystal-graphene?graphene?was exfoliated from bulk graphite by Novoselov and Geim in year 2004 using Scotch tape,a method currently known as micromechanical cleavage technique.The 2D materials feature unexpected physical,chemical,and electronic properties owing to the electron confinement in two dimensions.Nowadays,many new types of ultrathin 2D materials,such as transition metal dichalcogenides?TMDs?,hexagonal boron nitride?h-BN?,graphitic carbon nitride?g-C3N4?,black phosphorus?BP?,layered metal oxides,layered double hydroxides?LDHs?,2D metal organic frameworks?2D MOFs?,have been exploited in recent years.Such promising graphene-like 2D materials exhibit versatile properties on account of their similar structural features but varying compositions from graphene.The explorations on graphene and its analogues materials further enriched 2D materials families and the corresponding applications,such as electronics/optoelectronics,electro-or photocatalysis,energy storage and conversion,biomedical engineering,sensors,and more.Novel 2D nanomaterial systems derived from synthetic chemistry possess diverse physicochemical properties different from matrix materials,stimulating the emergence of many theranostic solutions and strategies for combating various pathological abnormalities.Inspired by the opportunities and challenges emerging in interdisciplinary science of nanomedicine,this study focused on the explorations for fantastic physicochemical performances of emerging 2D materials families?MXene and silicene?aiming for theranostic practices of disease models.From the perspectives of material design and synthesis,we investigated various aspects of phototherapy,diagnostic imaging and in vivo safety/compatibility of cancer therapy,and proposed potential solutions based on these novel 2D nanomaterials.The chapter two illustrates that MAX ceramic biomaterials exhibit the unique functionality for the photothermal ablation of cancer upon being exfoliated into ultrathin nanosheets within atomic thickness?MXene?.Ceramic biomaterials have been investigated for several decades,but their potential biomedical applications in cancer therapy have been paid much less attentions,mainly due to their lack of related material functionality for combating the cancer.As a paradigm,biocompatible Ti₃C₂nanosheets?MXenes?were successfully synthesized based on a two-step exfoliation strategy of MAX phase Ti₃AlC₂ by the combined HF etching and TPAOH intercalation.Especially,the high photothermal-conversion efficiency and in vitro/in vivo photothermal ablation of tumor of Ti₃C₂ nanosheets?MXenes?were revealed and demonstrated,not only in the intravenous administration of soybean phospholipid modified Ti₃C₂ nanosheets but also in the localized intratumoral implantation of a phase-changeable PLGA/Ti₃C₂ organic-inorganic hybrid.This chapter promises the great potential of Ti₃C₂ nanosheets?MXenes?as a novel ceramic photothermal agent used for cancer therapy,and may arouse much interest in exploring MXene-based ceramic biomaterials to benefit the biomedical applications.The chapter three demonstrates that MAX ceramic biomaterials exhibit unique functionalities for dual-mode PA/CT imaging and highly effective in vivo photothermal ablation of tumors upon being exfoliated into ultrathin nanosheets within atomic thickness?MXene?.Compared to Ti₃C₂ MXenes,these Ta₄C₃nanosheets possess biocompatible Ta element with high atomic number?Z=73?,which endows them with superior X-ray computed tomography?CT?contrast for CT imaging.As a paradigm,two-dimensional ultrathin tantalum carbide nanosheets?Ta₄C₃ MXenes?with nanosized lateral sizes were successfully synthesized based on a two-step liquid exfoliation strategy of MAX phase Ta₄AlC₃ by combined HF etching and probe sonication.The structural,electronic,and surface characteristics of the as-exfoliated nanosheets were revealed by various characterizations combined with first-principle calculations via Density Functional Theory.Especially,the superior photothermal-conversion performance?efficiency?of 44.7%?and in vitro/in vivo photothermal ablation of tumor by biocompatible soybean phospholipid-modified Ta₄C₃ nanosheets were systematically revealed and demonstrated.Based on the large family members of MXenes,this chapter may offer a paradigm that MXenes can achieve the specific biomedical applications?theranostic in this work?providing that their compositions and nanostructures are carefully tuned and optimized to meet the strict requirements of biomedicine.The chapter four introduces a novel type of 2D niobium carbide?Nb₂C?MXene with highly efficient in vivo photothermal ablation of mouse tumor xenografts in both NIR-I and NIR-II windows.The 2D Nb₂C nanosheets?NSs?was fabricated by a facile and scalable two-step liquid exfoliation method combining stepwise delamination and intercalation procedures.The ultrathin,lateral-nanosized Nb₂C NSs exhibited extraordinarily high photothermal conversion efficiency?36.4%at NIR-I and 45.65%at NIR-II?,as well as high photothermal stability.Most importantly,the Nb₂C NSs intrinsically features unique enzyme-responsive biodegradability to human myeloperoxidase,low phototoxicity and high biocompatibility.Especially,these surface-engineered Nb₂C NSs present highly efficient in vivo photothermal ablation and eradication of tumor in both NIR-I and NIR-II bio-windows.This chapter significantly broadens the application prospects of 2D MXenes by rationally designing their compositions and exploring related physiochemical properties,especially on phototherapy of cancer.Silicon-based biomaterials play an indispensable role in biomedical engineering,however,due to the lack of intrinsic functionalities of silicon,the applications of silicon-based nanomaterials have been largely limited to only serving as carriers for drug delivery systems.Meanwhile,the intrinsic poor biodegradation nature for silicon-based biomaterials as typical inorganic materials,also impedes their further in vivo biomedical use and clinical translation.The chapter five introduces that the rational design and wet chemical exfoliation synthesis of the two-dimensional?2D?silicene nanosheets.The traditional zero-dimensional?0D?nanoparticulate nanosystems have been transformed into 2D material systems,silicene nanosheets?SNSs?,which feature intriguing physiochemical natures for photo-triggered therapeutics and diagnostic imaging and greatly favorable biological effects of biocompatibility and biodegradation.Combining with DFT-based molecular dynamics?MD?calculations,the underlying mechanism of silicene interactions with bio-milieu and its degradation behavior have been probed under the specific simulated physiological condition.This chapter introduces a new form of silicon-based biomaterials with 2D structure featuring biodegradability,biocompatibility and multifunctionality for theranostic nanomedicine,which is expected to promise high clinical potentials.