**5. Conclusion**

*Novel Nanomaterials*

particles [133].

irrespective of the capping agents, at high concentrations (20–50 μg ml−1), whilst larger AgNPs did not display significant cytotoxic effects at all tested concentrations. The group additionally reported that at non-cytotoxic concentrations (10 μg ml−1), significant DNA damage was observed for all AgNPs independent of size and coating. In contrast, panda *et al*. reported no genotoxicity of AgNPs capped

Overall, it is difficult to establish the cytotoxic effect of AgNPs due to the differences in nanoparticle synthetic methods, their various sizes and capping agents and lastly the diverse evaluation tests used to determine toxicity. In fact, by using different organisms and/or culture cells there is no conclusive evaluation of AgNP toxicity [127]. However, bearing in mind the results presented in this review, it can be tentatively suggested that smaller sized AgNPs are more cytotoxic than larger

The physiochemical characteristics of metal nanoparticles render them applicable across a genre of multi-disciplinary fields for a variety of uses including catalysis [128]; micro-electronics [129]; solar energy conversion [130] amongst many others [131]. They have also been recognised for their potential in a number of medical applications [132]. However, the use of nanoparticles derived from physical and chemical synthetic routes raises health and toxicity concerns due to the nature of the reaction conditions which may ultimately affect the properties of the derived

Biologically derived nanoparticles provide a greener alternative to nanoparticles

With respect to biologically derived AgNPs, their major exploitation exists in the development of antimicrobial agents due to their renowned microbial inhibitory activities and with the current status on antimicrobial drug resistance, these particles are being extensively sought after as possible alternatives to antibiotics [1, 8].

derived from the aforementioned routes since, the synthesis methods used to derive these particles are clean and non-toxic [9]. As a result, they are suitable for a number of biomedical applications (**Table 1**) including: cancer therapy; drug delivery; tumour detection; genetic disorder diagnosis; tissue repair; cell labelling; antimicrobial development; targeting and immunoassays and yet to be discovered

**Plant Applications Reference** *Moringa oleifera* Anti-microbial [137] *Eclipta prostrata* Anti-protozoal [138] *Gelidiella acerosa* Anti-fungal [139] *Melia azedarach* Anti-cancer [140] *Lampranthus coccineus* Anti-viral [141] *Malephora lutea* Anti-Alzheimer [142] *Melia azedarach* Wound healing [143] *Ocimum sanctum* Anti-diabetic [144] *Allium sativum* Antioxidant [145]

*Selective applications of silver nanoparticles synthesised using plant extracts.*

with protein at 20–80 μg ml−1 for 24–55 nm sized particles [126].

**4. Potential applications of biologically derived nanoparticles**

sized particles at higher concentrations.

applications [37, 114, 132, 134–136].

**268**

**Table 1.**

In conclusion, it can be established that green synthetic strategies using plant and bacterial based extracts are promising alternatives to produce AgNPs. However, to produce AgNPs with enhanced bioactivities, morphological characteristics such as size and shape need to be finely tuned. Furthermore, the use of extracts with known medical value provides with attractive capping substrates that may potentially enhance the bioactivities of the produced particles.
