Nano Diamonds And Surface Functionalization

Introduction

In current scenario, the term nanotechnology is used world wide in context to pharmacologicals namely in biomedical science with its applications in bio-labelling, biosensors etc. and in novel drug delivery system for its implications in targeting. The applications of nanotechnology in different fields are necessary to change outlook of pharmaceutical industries for future prospective. Such issues like toxicity, incompatibility, instability, low safety regarding to predominant (traditional) drug, which allows scientists to established a new concept for drug delivery. To get the success upon dealing with such issues, term nanotechnology were came into the picture in 1990. With the help of this technology, it is possible to achieve improved characteristics of poorly water-soluble drugs, targeted drug delivery, visualization of specific drug target, loading capacity of drug for therapeutic agents, overcoming resistance and safety and biocompatibility of drug. Similarly, various types of nanomaterial are used for the biomedical applications and diagnostic purpose. Different types of nanomaterial like carbon nanotube, nanoparticle, metal rubber, quantum dots, Nano pore and fullerenes are available, but they have highest toxicity and less biocompatibility. So to overcome this issues, allotropes of carbon material known as a Nano diamonds have recently been included in this category.

Nowadays, Nano diamonds, a recent member of carbon nanomaterial are used frequently in the field of biomedical as well as non-biomedical by surface functionalization. Due to its versatile surface chemistry, Nano diamonds have also been discovered as a targeted drug delivery by surface modification with therapeutic agents like anti-cancer, anti-bacterial, anti-inflammatory etc. these nanoparticles are rhombus of carbon, having particle size of 5-20nm. Apart from this, proteins and polymers can be delivered safely and effectively by conjugation with Nano diamonds. This review article basically focuses on the surface functionalization of Nano diamonds with functional groups, biomolecules and polymers with its applications.

History

Most focusable zone in recent years of nanotechnology, defined as a nanodiamonds which were invented in 1963 in Russia. In Ukraine, there were Russian militarymen; who were continously tried to produce explosives materials such as bombs, missiles by detonation synthesis which led to generation of by-products in the form of dust particle or soot formation. There was an Ukranian scientist who observed this process continously and examined the dust particle. After research on those particles; Vladimir Denilenko found that; it was a nanoparticle having size of 2-10nm, which he termed as a nanodiamonds. His valuable observation is used to find out Nano diamonds. These Nano diamonds are also termed as a detonation Nano diamonds. Crude detonated Nano diamonds termed as a raw Nano diamonds is being produced in Russia and China since about 1990 by using expired product of composition B as a raw material by detonation synthesis.

Composition B includes 1:1 mixture of TNT (trinitrotoluene) (C7H5N3O6) –Hexogen (C3H6N6O6) on industrial scale. In last century, as a treatment option, DOX (doxorubicin) was prescribed but later due to its high toxicity and adverse effect of myelosuppression and cardiotoxicity, there was a need to replace It successfully, which provoked an intellect for exploring nanodiamonds. There lies an emerging need for better life and affordable healthcare, which demands extensive research in nanodiamonds.

Properties

Such problems like biocompatibility, safety, toxicity and many more was found in case of drug without Nano diamonds, hence to overcome these problems; therapeutic agents which are conjugate with the Nano diamonds for targeted drug delivery. Surface functionalization on the surface of Nano diamonds is safe and effective due to special characteristics as well as properties are observed in Nano diamonds. Nano diamonds have a useful properties like structural, biological, chemical, and optical.

• Structural: Nano diamonds are small size of primary monocrystalline particle. They are Available in variable size and narrow size fractions. Nano diamonds are small scale Nano particle having particle size about 2-10 nm so it is having Large surface area.
• Biological: High biocompatibility and low toxicity was observed in Nano diamonds which is very important properties of Nano diamonds. One advantageous characteristic of NDs is it can readily bind with bio-active substances with retained functional group.
• Chemical: It is a pH stable and radiation resistance. Vital properties of NDs is High chemical purity and large no of unpaired electrons are present on the surface, so functional groups, biomolecules and polymers can easily attached leads to effective surface functionalization.
• Optical: NDs having optical properties such as Photoluminescence, non-photo bleaching, nonblinking, high refractive index and optical transparency.

Production

Nano diamonds were obtained from natural sources like oils from various layers of earth, extra-terrestrial (meteorites and star system) and detonation soot. They were produced in industry by Russia and China from last few years. It is manufactured via different processing systems. Production of Nano diamonds includes three stages such as synthesis, processing and modification. Nano diamonds can be synthesized by using various techniques such as: Detonation, Ultra-sound cavitation, Laser ablation, Irradiation of graphite, Chlorination of carbon, Chemical vapor deposition, high pressure high temperature (HPHT), Micro-plasma-assisted ND formation, irradiation of graphite by ion beam and carbon onions irradiated by electron, but the most common and reliable method to synthesize Nano diamonds is by detonation process and the Nano diamonds which are obtained from this process are called as detonated Nano diamonds. After the synthesis of NDs, processing can be done by following three steps:

1. Purification: NDs are used in several biomedical applications so this phase become very important and crucial in processing. Throughout the production of NDs, they can be contaminated by various kinds of impurities such as metal, metal oxides, graphite carbon, reagents and various critical parameters of detonation process. To minimize these problems, NDs can be purified via different purification treatments including ozone treatment, heat treatment, membrane technology, ion-exchange techniques, microwave and certain reagents like ethylenediaminetetraaceticacid (EDTA) and diphenylamine.
2. De-aggregation: To prevent NDs from an aggregation, this step is required. Nano particles form an aggregate during synthesis and processing. Methods for de-aggregation are ball milling, jet milling, matrix assisted milling, ultrasonic disaggregation and dispersion, beads assisted sonic disintegration and thermal and chemical treatments.
3. Fractionation: NDs are generally dispersed into particular solvents to achieve fraction of define size range. High colloidal stability of ND Particles and alternatively density gradient centrifugation; methods used for fractionation.
4. Modification: In today’s era, NDs are repeatedly used in biomedical applications. Thus to improve certain characteristics of NDs, modification of purred NDs are essential.