**Author details**

also observed that immobilized enzyme shows cooperative interaction to enhance enzyme efficiency. Similarly, metal ions, such as copper, calcium and manganese, may also help enzyme in catalysis. Copper (Cu2+) is the most widely used metal with different enzymes. Cu2+ and laccase enzyme MPHN have been developed for detection of phenols. The prepared MPHN was adsorbed on filter, and a mixture of phenol and 4-aminoantipyrine was added to it. Laccaseassisted reaction of both compounds produced red antipyrine dyes in 5 minutes. The changes in color will be visible with the naked eye, and UV-visible spectrophotometer can be used for quantitative detection. The MPHN-coated filters are reusable and are much faster than chromatography and mass spectrometry based methods. Likewise, MPHN of Cu2+ and horseradish peroxidase was prepared for detection of phenol and hydrogen peroxide. This MPHN was able to detect very low amounts of phenol (1 μM) and hydrogen peroxide (0.5 μM) as change in color was observed with the naked eye. It has been found that hydrogen peroxide induces cell death at concentration higher than 50 μM and the limit of detection of free enzyme is around 20 μM. Thus, these MPHNs will be very efficient to detect slight changes in hydrogen peroxide efficiently even below its threshold level. Cu2+ and trypsin MPHN have been used to carry out proteolysis which is an important step in protein identification. The enzyme efficiency of proteo-

Another form of nanoflowers is synthesized using deoxyribonucleic acid (DNA) which, like proteins, possesses high number of nitrogen molecules and serves as a template for nanoflowers. In one study, a drug and a dye molecule was bonded to DNA that was used to synthesize nanoflowers. These nanoflowers showed multimodel property of drug delivery and imaging by using FRET technology. More recently, capsular MPHNs have been prepared with improved characteristics. This technique involved coating of MPHN with protamine and silica. Then, metallic core is removed from capsular MPHN system. Capsular nanoflowers show higher enzyme efficiency and improved stability in harsh environmental

Silica has been widely used in drug delivery due to its nontoxic and biocompatible nature. Silica shell has been applied to metallic nanoparticles to reduce their toxicity in various biomedical applications. Mesoporous silica nanoparticles (MSNPs) are silica materials with mesopores of up to 50 nm. They are also termed as hollow mesoporous silica nanoparticles due to the fact that mesopores are hollow. The advantages of MSNP are enhanced surface area and that hollow mesopores can be loaded with therapeutic molecules. First, MSNPs were loaded with drugs. Later, MSNPs were used for the delivery of different dyes and macromolecules such as enzymes. MSNP hybrids have been prepared with both organic and inorganic materials. One problem with the use of MSNP is the leakage of drugs from pores. Sreejith et al. [117] used graphene oxide (GO) coating on MSNP to prevent leakage of drugs. After drug loading, GO coating is applied which acts as blanket to physically block the pores. GO coating also prevents encapsulated drug from environmental degradation. In addition to

applications in drug delivery, MSNPs are also used for diagnosis and imaging.

Maji et al. [118] prepared MSNP-GNP (gold nanoparticle) hybrids for detection of hydrogen peroxide. They coated MSNP with graphene oxide, and GNPs were coated on this surface.

lytic MPHN is similar or superior to free enzyme but are fast and reusable.

conditions.

**4.4. Mesoporous silica hybrid nanoparticles**

76 Advanced Technology for Delivering Therapeutics

Asadullah Madni\*, Nayab Tahir, Mubashar Rehman, Ahmed Raza, Muhammad Ahmad Mahmood, Muhammad Imran Khan and Prince Muhammad Kashif

\*Address all correspondence to: asadpharmacist@hotmail.com

Faculty of Pharmacy and Alternative Medicine, The Islamia University of Bahawalpur, Bahawalpur, Pakistan
