**Conflict of interest**

*Multidisciplinary Approach for Colorectal Cancer*

ATP-binding cassette subfamily G2 (ABCG2) porphyrin-based targeted PDT.

Single chain variable fragments (scFvs), antibody fragments

HER2 receptor or jacalin, a lectin specific for carbohydrate T antigen on PEG Gold nanoparticles

*Active Targeting PDT PS drug delivery mechanisms within in vitro and in vivo CRC.*

Peroxisomal proliferator-activated receptor gamma (PPARγ) ligand troglitazone

*In vitro* **and** *in vivo* **PDT CRC research Photosensitizer Active drug delivery system**

Pyropheophorbide-a (PPa) protoporphyrin

Pyropheophorbide-a methyl ester (PPME)

Zinc phthalocyanine

Verteporfin succinimidyl ester

(C11Pc)

**Table 3.**

**54**

**Acknowledgements**

**8. Conclusion**

actively enhancing PS drug uptake.

From this chapter it can be observed that PDT is most definitely a highly effective and alternative therapeutic treatment for CRC [8]. However, conventional PS drug delivery applications have numerous limitations in relation to solubility and poor tumor subcellular localization specificity [26]. Nevertheless, NP PS drug delivery systems which are surface functionalized with various tumor-targeting moieties can help overcoming some of these limitations be passively, as well as

HER2-) cells.

**Remarks Ref.**

[111]

[112]

[44]

[113]

PS drug delivery was improved within *in vitro* HT29 cells show high levels of ABCG2 expression with

Enhanced uptake in DLD-1 CRC *in vitro* cells, with significant growth retardation and apoptotic cell death in a PDT dose-dependent manner.

Improved uptake and within *in vitro* and *in vivo* PDT applications it effectively killed tumor LoVo (CEA+,

HT-29 CRC cells reported enhanced targeted PDT

with 80–90% cell death being noted.

significant PDT induced cell damage.

In this chapter, we have shown that there are many positive and promising research studies being conducted *in vitro* and *in vivo*, for the use of PDT in CRC treatment (**Table 1**). We have also evidenced the remarkable potential of passivation NP PS drug carrier platforms (**Table 2**) and specific receptor based PS drug active targeting (**Table 3**), in order to promote the selective absorption of PS drugs in target CRC tumor sites only and so avoid unwanted side effects, as well as overall enhance the PDT treatment of CRC. However, it must be noted that the research studies which have been reported in **Tables 2** and **3** are within early stages of *in vitro* and *in vivo* research and no clinical trials have been performed as of yet. Thus, researchers need to start further exploring specific functionalized NP PS drug delivery platforms for the targeted drug delivery of PSs and effective PDT treatment of CRC within pre-clinical and clinical trials in order to develop optimized standards for this form of CRC therapy [8]. The findings from these studies should drive the application of targeted PDT PS drug delivery to the forefront of oncological interventions as a possible treatment modality for the eradication of CRC.

The authors sincerely thank the University of Johannesburg, South African Research Chairs Initiative of the Department of Science and Technology and

The authors confirm that this chapter has no conflict of interest.
